The gearing ratios for the rx-8 are one unknown that we haven’t really discussed in much detail. There has been some talk and much speculation about the rx-8’s top speed, mileage, 0-60 times, ¼ mile times etc but they are *all* dependent on gearing.

Since the rx-8 was designed to seat 4 people and the gearing/diff ratios should take that into account and be much higher than the ratios on the last rx-7. What would everybody like to see the gearing ratios end up at?

I would propose the following aggressive and closely spaced gearing to give the best 0-60, ¼ mile, mileage and utility. Gears 1 thru 5 are aggressively geared and closely spaced. 6th gear is only overdrive gear and is spaced a bit apart from 5th . The .84 6th gear is mainly for fuel economy at highway/freeway speeds but will also lead to a very high top speed. Because of the renesis' wide power band and flat torque curve, the rx-8 will be very driveable (until we hear the dang buzzer). :D

Rear wheels = 225 45 18
Diff - 4.1
1st – 4.02
2nd – 2.46
3rd – 1.77
4th – 1.33
5th – 1.08
6th - 0.84

1st gear at 3500 rpm would be approx 16 mph.
2nd gear will hit 60 mph near the hp peak.
55 mph would be approx 2750 rpm in 6th gear.

Would there be any reason why the above gearing would not be practical? Below is also a chart which gives the speeds per rpm for each gear.

RPM 1 2 3 4 5 6
1000 4.6 7.5 10.4 13.8 17.0 21.9
1500 6.8 11.2 15.6 20.7 25.5 32.8
2000 9.1 14.9 20.7 27.6 34.0 43.7
2500 11.4 18.7 25.9 34.5 42.5 54.6
3000 13.7 22.4 31.1 41.4 51.0 65.6
3500 16.0 26.1 36.3 48.3 59.5 76.5
4000 18.3 29.8 41.5 55.2 68.0 87.4
4500 20.5 33.6 46.7 62.1 76.5 98.3
5000 22.8 37.3 51.9 69.0 85.0 109.3
5500 25.1 41.0 57.0 75.9 93.5 120.2
6000 27.4 44.8 62.2 82.8 102.0 131.1
6500 29.7 48.5 67.4 89.7 110.5 142.1
7000 32.0 52.2 72.6 96.6 119.0 153.0
7500 34.2 56.0 77.8 103.5 127.5 163.9
8000 36.5 59.7 83.0 110.4 136.0 ----
8500 38.8 63.4 88.2 117.3 144.5 ----
9000 41.1 67.2 93.3 124.2 153.0 ----

If the rx-8 were geared as such, the 0-60 times will *easily* be well less than 6 seconds and the 1/4 mile might be less than 14?
:eek:

Brian

Oops, the tabs in the chart disappeared. I think the below chart will be easier to read:

RPM````````1`````````2`````````3 `````````4`````````5`````````6
1000``````4.6``````` 7.5``````` 10.4`````` 13.8`````` 17.0`````` 21.9
1500``````6.8``````` 11.2`````` 15.6`````` 20.7`````` 25.5`````` 32.8
2000``````9.1``````` 14.9`````` 20.7`````` 27.6`````` 34.0`````` 43.7
2500``````11.4`````` 18.7`````` 25.9`````` 34.5`````` 42.5`````` 54.6
3000``````13.7`````` 22.4`````` 31.1`````` 41.4`````` 51.0`````` 65.6
3500``````16.0`````` 26.1`````` 36.3`````` 48.3`````` 59.5`````` 76.5
4000``````18.3`````` 29.8`````` 41.5`````` 55.2`````` 68.0`````` 87.4
4500``````20.5`````` 33.6`````` 46.7`````` 62.1`````` 76.5`````` 98.3
5000``````22.8`````` 37.3`````` 51.9`````` 69.0`````` 85.0`````` 109.3
5500``````25.1`````` 41.0`````` 57.0`````` 75.9`````` 93.5`````` 120.2
6000``````27.4`````` 44.8`````` 62.2`````` 82.8`````` 102.0`````131.1
6500``````29.7`````` 48.5`````` 67.4`````` 89.7`````` 110.5`````142.1
7000``````32.0`````` 52.2`````` 72.6`````` 96.6`````` 119.0`````153.0
7500``````34.2`````` 56.0`````` 77.8`````` 103.5`````127.5`````163.9
8000``````36.5`````` 59.7`````` 83.0`````` 110.4`````136.0`````----
8500``````38.8`````` 63.4`````` 88.2`````` 117.3`````144.5`````----
9000``````41.1`````` 67.2`````` 93.3`````` 124.2`````153.0`````----


Brian

I'd rather see it a little shorter than that, but maybe that's just me. Perhaps 5-10 MPH lower in each gear at redline. I don't do a lot of high-speed cruising, but I do value quick acceleration.

Looks good,

I agree with Grimace to some extent, perhaps a little shorter... not as much as 10Mph though...

I do think that 6th should be a real long legged cruiser as suggested... I often cruise near 90-100Mph and when in germany I had the chance to cruise at 135+ for about 200 miles.... don't want to be ragging the engine at high speed cruising...

One thing though.... If you want to reach 60 in second, for 0-60 times... it must be 62 not 60 before the rev limit... because european tests are to 100Kph (62Mph).

Originally posted by BlueAdept
One thing though.... If you want to reach 60 in second, for 0-60 times... it must be 62 not 60 before the rev limit... because european tests are to 100Kph (62Mph).

Hi BlueAdept,

With the gearing that I suggested, 2nd gear would actually be going at 67.2 mph at the rev limit and 63.4 at the hp peak. I am hoping that the rx-8 will come out as aggressively geared from 1st thru 5th as my example (or even a little shorter).

The renesis is really different than anything out there though. Does anyone know any other production engine that comes close to (or beats?) 6000 rpm of greater than 90% torque?!?!?!

Brian

Originally posted by BlueAdept
I do think that 6th should be a real long legged cruiser as suggested... I often cruise near 90-100Mph and when in germany I had the chance to cruise at 135+ for about 200 miles.... don't want to be ragging the engine at high speed cruising...

If the rx-8 6th gear was .84 as in the example, 135 mph would still be approx 1200 *below* the torque peak. The car would be *begging* you to at least take it 1200 more rpms to it's torque peak at 163 mph (or whatever the electronically limited top speed would be). :D

You wouldn't be ragging the engine and probably wouldn't even notice the revs were that high until you heard the buzzer. :D

Brian

Originally posted by Buger


If the rx-8 6th gear was .84 as in the example, 135 mph would still be approx 1200 *below* the torque peak. The car would be *begging* you to at least take it 1200 more rpms to it's torque peak at 163 mph (or whatever the electronically limited top speed would be). :D

You wouldn't be ragging the engine and probably wouldn't even notice the revs were that high until you heard the buzzer. :D

Brian

Oh, absolutely,, I wasn't complaining about your numbers... but Grimace was suggesting lowering the ratios... I don't mind that, but 6th must be long legged...

As for the 0-62 thing... I don't think we are exactly sure where the redline will be...

Originally posted by BlueAdept

Oh, absolutely,, I wasn't complaining about your numbers... but Grimace was suggesting lowering the ratios... I don't mind that, but 6th must be long legged...

As for the 0-62 thing... I don't think we are exactly sure where the redline will be...

Unfortunately, we will probably have to wait until at least January before we get more concrete info on many of the particulars. :(

Brian

Gear ratios OK to me. Perhaps a little taller, if anything.

Originally posted by Donny Boy
Gear ratios OK to me. Perhaps a little taller, if anything.

I can't see taller myself... we're talking about a 6 speed box that can get to 60 in second.... even that's probably a sacrafice to get good 0-60 times.

Originally posted by BlueAdept


I can't see taller myself... we're talking about a 6 speed box that can get to 60 in second.... even that's probably a sacrafice to get good 0-60 times.

Taller would be a mistake. You wouldn't get into the power band above 3500 RPM in first gear for 18-odd MPH. I'd favor shorter so that people get into the 4000 RPM powerband quickly. That way it feels more powerful. SHorter gearing takes advantage of the high-RPM, low-torque nature of the engine, while tall gearing would actually make the car feel sluggish.

Originally posted by PatrickB


Taller would be a mistake. You wouldn't get into the power band above 3500 RPM in first gear for 18-odd MPH. I'd favor shorter so that people get into the 4000 RPM powerband quickly. That way it feels more powerful. SHorter gearing takes advantage of the high-RPM, low-torque nature of the engine, while tall gearing would actually make the car feel sluggish.

Exactly... I agree they could all be a little shorter, except 6th which is just about right in my eyes,

I was playing around with CarTest (a car performance calculator) to see how different gearing might affect the acceleration of the RX-8. On my own, I came up with these values for gearing:

Final - 4.10
1st - 3.70
2nd - 2.65
3rd - 1.90
4th - 1.45
5th - 1.05
6th - 0.75

My ratios give the following results:

0-60: 5.35
1/4: 14.0 @ 102.0
Top Speed: 161 MPH in 121.6 seconds

The values suggested by Buger - His 1st and 2nd are shorter, while his 3rd, 4th, and 5th are taller:

Final - 4.10
1st - 4.02
2nd - 2.46
3rd - 1.77
4th - 1.33
5th - 1.08
6th - 0.84

Here are CarTest's results for Buger's ratios:

0-60: 5.40
1/4: 14.0 @ 101.4
Top Speed: 160 in 111.96 seconds.

This is only a computer simulation, so take it for what it is worth, but it appears that my slightly taller first two gears will actually help 0-60 and 1/4 acceleration, albeit ever so slightly. However, Buger's taller 3rd and 4th seem to greatly improve time to top speed. It seems that taller is better from this starting point. I'll play around with the numbers some more and see if I can improve on things.

Note that 6th gear has no effect on any of these tests, as top speed occurs at redline in 5th for both of our gear sets.

Other note: The simulations were based on a 2800 weight.

RedRotaryRocket

Good posts from you and the others. Why not use 2970 for the weight instead of 2800 like you've done. until we hear differently, we are better off using the last weight given by Mazda. if they better it by production, all the better but for now, let's see what the simulations come out with at the weight of 2970.
Just a suggestion.:rolleyes:

Boowana,

Ask and you shall receive. :D Actually, the numbers using 2800 lbs are probably too optimistic, since the software assumes that the weight includes the driver.

I re-ran the simulation using a weight of 3170 (2970 + 200 lb driver). Here are the results:

My gear set:
0-60: 5.9
1/4: 14.6 @ 98.2
Top Speed: 160 in 140.03 seconds

Buger's gear set:
0-60: 6.0
1/4: 14.5 @ 98.3
Top Speed: 159 in 124.62 seconds

Howzzzat?

Originally posted by RedRotaryRocket
Boowana,

Ask and you shall receive. :D Actually, the numbers using 2800 lbs are probably too optimistic, since the software assumes that the weight includes the driver.

I re-ran the simulation using a weight of 3170 (2970 + 200 lb driver). Here are the results:

My gear set:
0-60: 5.9
1/4: 14.6 @ 98.2
Top Speed: 160 in 140.03 seconds

Buger's gear set:
0-60: 6.0
1/4: 14.5 @ 98.3
Top Speed: 159 in 124.62 seconds

Howzzzat?

Interesting software....

I don't think it could be that hard to write somthing along those lines that did an "Auto optimisation"...

And the nissan guys just realized what power to weight ratio meant. I hope those new calculations are too conservative because I would love to easily be in the 13's with a few mods. That really shows how weight effects performance.

Have you plugged in stats from known cars and seen how they matched up?

I also just realized that none are 1:1 which one of them will have to be. In most sets it is fourth but your fifth is close @1.08 so try the scenario with it like that please?

The software actually comes with stats from many vehicles...generally it's within 2 or 3 tenths as far as 0-60 or 1/4 mile times are concerned. Plus or minus 2 or 3 tenths is still a pretty big spread, but it's not too bad for getting "in the ballpark"

Originally posted by SPDFRK
I also just realized that none are 1:1 which one of them will have to be. In most sets it is fourth but your fifth is close @1.08 so try the scenario with it like that please?

Hi spdfrk,

I was aware that 4th was usually the 1:1 gear but before coming up with my original gear ratios, I found that the s2000 had the below gearing:

Final - 4.10
1st - 3.133
2nd - 2.045
3rd - 1.481
4th - 1.161
5th - 0.971
6th - 0.811

Oddly enough, the s2000 has no 1:1 gear. Honda geared the s2000 so that the gears are nicely spaced and it actually has 2 overdrive gears. Too bad the s2000 doesn't have a renesis torque curve. ;)

Originally posted by RedRotaryRocket
I was playing around with CarTest (a car performance calculator) to see how different gearing might affect the acceleration of the RX-8. On my own, I came up with these values for gearing:

Final - 4.10
1st - 3.70
2nd - 2.65
3rd - 1.90
4th - 1.45
5th - 1.05
6th - 0.75

Nice numbers RRR! I like that your 2nd thru 5th gears are a little shorter than mine. I think the only thing hurting your 0-60 time is the taller 1st gear.

I also think that your 6th gear is probably more in line with what Mazda has done in the past as rx-7s usually had their top gear rpms at around 2100 - 2200 at 55 mph.

That cartest software is pretty cool too. I downloaded the demo version and it puts out tons of graphs and info, even a mpg graph per gear! The demo version only lets you analyze the cars already in its database though. How about some revised gearing numbers:

Final - 4.10
1st - 4.10
2nd - 2.61
3rd - 1.84
4th - 1.39
5th - 1.06
6th - 0.75

I like your very short second gear but I made it just a *little* longer. I also made 1st gear shorter to maintain even spacing and because a sports car with seating for 4 adults should have ample torque in first gear. I slightly shortened gears 3 thru 5 and made 6th gear even longer as one of the goals of Mazda was that the car have much improved mileage. Could you try the below gearing numbers in Cartest?

Brian

Brian,

I ran your new numbers, but I made a change to your 5th gear...I made it 1.03 as that maximizes top speed.
Here's the results using your revised gearing (with 1.03 5th):

0-60: 5.80
1/4: 14.5 @ 98.0 MPH
Top Speed: 160.3 in 145.13 seconds

That's based on a test weight of 3170 lbs, so compare these numbers to the later set I generated...you've picked up 0.2 seconds to 60...pretty good!

Eric

Originally posted by RedRotaryRocket
Brian,

I ran your new numbers, but I made a change to your 5th gear...I made it 1.03 as that maximizes top speed.
Here's the results using your revised gearing (with 1.03 5th):

0-60: 5.80
1/4: 14.5 @ 98.0 MPH
Top Speed: 160.3 in 145.13 seconds

That's based on a test weight of 3170 lbs, so compare these numbers to the later set I generated...you've picked up 0.2 seconds to 60...pretty good!

Eric
It's DEFINATELY going to be 2940 lbs or LESS, so re-do those figures and lemme see those times again :)

Originally posted by Hercules

It's DEFINATELY going to be 2940 lbs or LESS, so re-do those figures and lemme see those times again :)

yeah herc but ya gotta add the weight for the human ( or rotorhead) driving:p

Originally posted by zoom44


yeah herc but ya gotta add the weight for the human ( or rotorhead) driving:p
Hrmm good point :)

How do they test cars in magazines and such?

Try it with 3115 lbs :)

That's so it accounts for ME in the car :P (175 lbs hehehe)

Originally posted by Hercules
Try it with 3115 lbs :)

That's so it accounts for ME in the car :P (175 lbs hehehe)

I just bought cartest2000 and have some good news. According to the help menu in the program:

"CAR CURB WEIGHT: Enter the curb weight of the car excluding the driver, passengers, or fuel. "

Furthermore, if you click "create car specific model parameters", you will see where you can specify the "weight of driver". :D

Unfortunately, I just got done with a long day at work and I'm going to sleep now. I will try entering the rx-8 hp curve values into the program tomorrow morning and see what the program will come up with for a curb weight of 2900 lbs. :)

Brian

Cartest normally uses a hp/torque curve profile for cars which is modified to match the peak hp/torque numbers that are entered. Since the renesis hp/torque curves are very different than a normal piston engine, I modified the hp/torque curves to match the renesis. (see attachment)

Below are some of the parameters that were used:

hp:........... 250 @ 8500
torque:.... 159 @ 7500
redline:.... 9000 rpm
wheels: ... 225/45R18

Diff - 4.1
1st - 4.10
2nd - 2.61
3rd - 1.84
4th - 1.39
5th - 1.06
6th - 0.75

curb weight:........ 2900 lbs
driver weight:..... 160 lbs
drag coeff:.......... .29 (estimated using value from Mazda Millenia)
grnd clearance:... 4.9" (estimated using value from Mazda Millenia)
launch rpm: ........ 2000 (optimum est by cartest using all data)

Below are the some of the results:

0-60: ........... 5.74 seconds
1/4: ............. 14.36 @ 99.08 MPH
Top Speed: .. 160.69 in 131.37 seconds
Mileage: ....... 20.4/32.1 mpg (combined 24.4)

Below are some results with a 3000 lb curb weight:

0-60: ........... 5.89 seconds
1/4: ............. 14.49 @ 98.19 MPH
Top Speed: .. 160.39 in 134.70 seconds

Below are some results with a 2800 lb curb weight:

0-60: ........... 5.6 seconds
1/4: ............. 14.23 @ 99.97 MPH
Top Speed: .. 160.97 in 127.44 seconds

It will be interesting to see what the final weight and gearing specs end up at. This should give us all some idea of what may be possible.

Brian

Thanks Buger for the great info! Do you know it the 0-62 (0-100km/h) will be very different?

holy effin' eff... 0-60 mph in 5.6s?? again, holy...

i know that this approximation (using approximated and guesstimated numbers) is only an approximation (using approximated and guesstimated numbers), but still man, that's pretty damn fast for a sports sedan...

Thanks.:D

Much better.:p

I can see I will have to go on a major diet:( Oh well, it'll be worth it. Now I have a real reason to drop a few.

Buger,

Nice numbers. It sounds like your version of cartest is much more sophistocated than mine...mine must be some old demo version or something...it's dos based and I downloaded it for free almost two years ago! Needless to say, mine doesn't have a help menu and only accepts one weight, entitled "test weight". Since you've got the fancy-schmancy version, we'll let you generate the numbers from now on :D

Does CarTest2000 account for drivetrain configuration and losses?

That's a big 10-4 good buddy.

Or....

Yes.

:)

Originally posted by sheylen
Thanks Buger for the great info! Do you know it the 0-62 (0-100km/h) will be very different?
Hi Sheylen,

It shouldn't make much of a difference. Add about .02 seconds at that speed to the 0 - 60 time.

Originally posted by RedRotaryRocket
Nice numbers. It sounds like your version of cartest is much more sophistocated than mine...mine must be some old demo version or something...it's dos based and I downloaded it for free almost two years ago!

I got the new version from www.cartest2000.com. I think the same guy has been tweaking it a bit. I can run some other numbers if anybody wants to but it would be good to buy a version to reward the guy for all of his work.

Originally posted by BryanH
Does CarTest2000 account for drivetrain configuration and losses?

Yes, it appears to estimate drivetrain losses pretty closely but you can modify the losses if you have more specific information. See the attached screenshot of some of the parameters.

Brian

Thanks again:cool:

Here is the attachment with some of the drivetrain loss parameters (it was too big earlier):

The performance of the 1999 Mustang gt coupe and the estimated performance of the rx-8 are pretty close. It would be interesting to look at how two closely matched performance cars with vastly different approaches compare. The Mustang has far greater torque but the Rx-8 will have a much higher redline.

Attached are a couple of curves comparing the 1999 Mustang gt coupe and the rx-8 acceleration in first gear. The graph on the left illustrates how the renesis can pull over a much wider rpm range (almost 60% longer) than the Mustang v8.

In the graph on the right, you can see how the torque curve of the example rx-8 was shortened to approx the same speed range of the Mustang by shorter gearing. Although the Mustang engine has a huge advantage in torque(302 - 159), it is also approx 300 pounds heavier in this example (3205 vs 2900). The Mustang still pulls harder (by approx .1g) at its torque peak but we can see that the sample rx-8 pulls harder at the low and high ends of its curve.

The example rx-8 has the following gearing:

Diff - 4.1
1st - 4.10 * 4.1 = 16.81
2nd - 2.61 * 4.1 = 10.701
3rd - 1.84 * 4.1 = 7.544
4th - 1.39 * 4.1 = 5.699
5th - 1.06 * 4.1 = 4.346
6th - 0.75 * 4.1 = 3.075

The 99 Mustang GT has the following gearing:

Diff - 4.1
1st - 3.37 * 3.27 = 11.02
2nd - 1.99 * 3.27 = 6.507
3rd - 1.33 * 3.27 = 4.349
4th - 1.00 * 3.27 = 3.27
5th - 0.67 * 3.27 = 2.191

With the above gearing, the renesis will turn almost 17 times before the rear wheels turn once in first gear. The mustang engine will turn a little over 11 times before its rear wheels turn once in first gear. The difference in gearing and weight mitigate the peak torque advantage that the mustang has. With the above gearing, simulated world (not real world) testing shows that the rx-8 actually beats the mustang in 0-60, 1/4 mile and top speed.

Two more graphs compare the drive power of the 2 cars thru the gears. You can see how the higher drag coefficient affects the top speed of the mustang.

If you would could you try adding 50 hp to the top end. Just to show us what kind of times the mazdaspeed version of the rx8 would produce. I would think the 50 hp would come in late in the powerband.

Thanks
Ryan Fritts

What kind of swept area are you using for the top speed calculation? If the RX-7 had about 1.9 square meter frontal area, how does the RX-8 compare.

What was the coefficient of drag of the RX-7? 0.35?

Also since the Miata 6 speed has a 1:1 5th gear, so should the RX-8. That benefits top speed because the power doesn't flow through a gear mesh in the transmission.

Originally posted by MikeW
What kind of swept area are you using for the top speed calculation? If the RX-7 had about 1.9 square meter frontal area, how does the RX-8 compare.

What was the coefficient of drag of the RX-7? 0.35?

Also since the Miata 6 speed has a 1:1 5th gear, so should the RX-8. That benefits top speed because the power doesn't flow through a gear mesh in the transmission.

0.35 is very high these days... I'd be surprised if a modern design was above 0.30... infact I'd be surprised if the RX-7 was that high!

A quick web search seems to indicate that the FD RX-7 had a drag coefficient of 0.30.....

Originally posted by fritts
If you would could you try adding 50 hp to the top end. Just to show us what kind of times the mazdaspeed version of the rx8 would produce. I would think the 50 hp would come in late in the powerband.

Hi Ryan,

I am at work now but will try using the single turbo torque profile with the extra 50 hp and the added weight tomorrow morning at home.

Originally posted by MikeW

What kind of swept area are you using for the top speed calculation? If the RX-7 had about 1.9 square meter frontal area, how does the RX-8 compare.

What was the coefficient of drag of the RX-7? 0.35?

Also since the Miata 6 speed has a 1:1 5th gear, so should the RX-8. That benefits top speed because the power doesn't flow through a gear mesh in the transmission. .

Hi Mike,

As there has been no real info on the frontal area of the rx-8, I let cartest estimate it from the given parameters. It is an optional field and the help menu says that "CarTest will estimate it if it is not known more precisely". I could probably try some values to geta ballpark figure of what cartest is using though.

The drag coefficient of the 3rd gen rx-7 was .29. I estimated .29 for the rx-8 as well since the Mazda Millenia also had the same coefficient. Surprisingly, even the 2003 Toyota Corolla has a low drag coefficient of .296. It may be more conservative to estimate the rx-8 drag as .30 but no more than that. A convertible version of the rx-8 (if it is ever made) might have a drag of something close to .35 but the rx-8 coming out next year should have .29 or .30.

It is a good idea to try a 1:1 ratio in 5th gear as it is much more common on 6 speeds than the gearing #s I used. There are several cars out there without a 1:1 ratio gear but you make a good point that having a 1:1 5th gear could marginally reduce frictional losses for that gear.

I think the best ratio for top speed was somewhere around 1.04 or 1.05 to 1 because the drag losses curve meets the 5th gear torque curve close to the highest peak. A 1:1 5th would be more fuel efficient though and would probably be more in line of what Mazda is planning. I will try a 1:1 5th tomorrow morning and move 3rd and 4th to space them evenly with the new 5th gear.

Brian

A google search on the web comes up with conflicting info for the Cd of the 3rd gen. Most places generally quote .29 or .30.

I remember reading that the base had a .29 Cd while the r1 had a .31 because of the added body items.

I also remember reading that the 2nd gen rx-7 had a similar Cd of .29 to .31 depending on the model.

I fully expect the rx-8 to come in at a similar range of .29 - .30 for the base model. The Cd doesn't make too much of an impact at lower speeds but is the major factor in limiting top speeds of cars.

The top speed of the rx-8 is definitely not a factor for me as I would not like risking a ticket at anything over 100 anyway.

Brian

Most Japanese/German (soon to be american) companies like to use Cw instead of Cd. Well Honda doesn't.

The Insight is 0.25 Cd, Toyota claims that the Lexus LS430 is also 0.25 (my ass!!!) I would believe 0.25 Cw if the car was lowered to its bump stop (air suspension) and the wheels weren't rolling in a wind tunnel.

Cw differs from Cd in that Cw is what the drag from blowing air at a car. Cd is what results from hitting stationary air (Real Driving)


I would hope that the RX-8 has low front/rear lift rather than a remarkably low Cd

Originally posted by MikeW
Most Japanese/German (soon to be american) companies like to use Cw instead of Cd. Well Honda doesn't.

Cw differs from Cd in that Cw is what the drag from blowing air at a car. Cd is what results from hitting stationary air (Real Driving)



How do you test Cd then if stationary in a wind tunnel doesn't cut it?

Originally posted by MikeW
What kind of swept area are you using for the top speed calculation? If the RX-7 had about 1.9 square meter frontal area, how does the RX-8 compare.

What was the coefficient of drag of the RX-7? 0.35?

Also since the Miata 6 speed has a 1:1 5th gear, so should the RX-8. That benefits top speed because the power doesn't flow through a gear mesh in the transmission.

Trying different values, it appears that cartest estimated the frontal area to be 23.821 sq ft. This seems a bit high to me as I found a website that had the Mazda 929 at 20.76 while being both wider and taller than the rx-8. Whatever the case, 20.44 sq ft (1.9 sq m) seems to be reasonable number so I will use that number for the rx-8 from now on. A quick check on cartest shows that the change in frontal area increased top speed by 5 mph and marginally decreased the 0-60 and 1/4 mile times.

While researching some of the variables of drag, I found some good info on Cd and frontal area. An excerpt from the site (http://www.thirdgen.org/newdesign/tech/groundeffects.shtml) is below:

Coefficient of drag is the most widely used number in relating the Aerodynamic efficiency of a car, and is very misleading. It is just a measure of how much out of 100% (like a barn door) a vehicle lets air flow around it. Typically sports cars have coefficients of between .28 and .45 (Viper roadster uggh!). The better (lower) the number is, the easier it is for air to pass around a car. It can be misleading because I recently read an ad in MT,and it claimed that the '97 Infiniti Q45 has the best CD of any production car (I think it was .27). You don't realize that the car has 10" more height, and a few inches more width than a third generation f-body (length isn't a factor). This means that it has more sq feet of air to push out of the way.

A good example of frontal area is the Mazda Miata. The car has a greater CD than an f-body (camaro?), but because its frontal area is tiny (I think it is 16.5 sq ft), it is more aerodynamically efficient.I use an equation to compare cars with different CD and Frontal Area figure, the number generated is merely a factor to be compared 1:1.

CD x Frontal Area(sq ft) = factor #
It works well for direct comparisons, because doing it the long way would take 10 minutes to compute (true engineering method).

Trying different values in the optional field tire circumference, it appears that cartest estimated the value to be 82.44 inches while a 225/45R18 should have a tire circumference of 81.59 inches. Real world circumference will be a little smaller because of the weight of the car so I just used a value of 81 inches. Note that this has the effect of additionally gearing the car an additional 1.75%.

The changed parameters for the new test are below:

frontal area: ................ 20.44 sq ft (instead of cartest est 23.821)
wheel/tire circumference: 81 inches (instead of cartest est 82.44)

Diff - 4.1
1st - 4.10 * 4.1 = 16.81
2nd - 2.65 * 4.1 = 10.865
3rd - 1.83 * 4.1 = 7.503
4th - 1.33 * 4.1 = 5.453
5th - 1.00 * 4.1 = 4.1
6th - 0.75 * 4.1 = 3.075

curb weight:........ 2900 lbs
launch rpm: ........ 1800 (optimum est by cartest using new data)

Below are the some of the results:

0-60: ............ 5.64 seconds
1/4: ............. 14.32 @ 99.32 MPH
0-160: ........... 57.28 seconds
Top Speed: ....... 168.49 in 144.82 seconds

Brian

Brian,
Is that estimated 0-60 time for the 300 hp mazdaspeed version?

Originally posted by fritts
Brian,
Is that estimated 0-60 time for the 300 hp mazdaspeed version?

That was for the na version with revised gearing, front area and wheel parameters.

I just did a quick run with 100 pounds added weight and using the standard torque curve with the turbo profile and the below hp/torque figures:

hp: .......... 300@8500 rpm
torque: ... 220@6500 rpm

The rest of the parameters are the same as for my previous post. Below are the some of the results:

0-60: ............ 4.77 seconds
1/4: ............. 13.43 @ 107.49 MPH
Top Speed: ....... 178.47 in 171.67 seconds

I really wanted to do some research to estimate what numbers would be reasonable to input but I didn't have the time. The above numbers seem a bit unreal don't they?

Brian

Those top speed seem very unrealistic. I would hope that the RX-8 (regular) would do 160, and a 300 hp version should do 170 (hopefully).


A wind tunnel can be used for estimating the aero drag, and so can a computer model. Empirical testing determines how much high the real Cd is.

Anyone remember 'roll down' testing in Motor Trend many many years ago.

Originally posted by MikeW
Those top speed seem very unrealistic. I would hope that the RX-8 (regular) would do 160, and a 300 hp version should do 170 (hopefully).


A wind tunnel can be used for estimating the aero drag, and so can a computer model. Empirical testing determines how much high the real Cd is.

Anyone remember 'roll down' testing in Motor Trend many many years ago.
Not like it matters anyway, you'll never get up to that speed, even on a track, unless it's an oval :D

I have gotten up to 150 in an E36 M3 on a straightaway, but otherwise I stay around the 80-85 limit on the highways.

Excuse me. I'm not as smart as you guys are when it comes to cars, but I do know more than most. Why haven't made 7 speed manuals yet?

Originally posted by ilovepotatos
Excuse me. I'm not as smart as you guys are when it comes to cars, but I do know more than most. Why haven't made 7 speed manuals yet?

6-speed manuals are already reaching top acceleration and top speeds in 5th gear, with the 6th gear for highway cruising. With 7 you'd either be adding a wasteful cruising gear, or making the low-end shift-points even closer together. Obviously we don't want the former; the later is only justifiable from a performance point of view if it increases gearing enough to offset the increased shifting. From a drivability point of view, it also makes the car more cumbersome to drive in stop-and-go traffic. And all of this has to take into account the increased cost of a 7-speed.

Thanks Pat!

Originally posted by PatrickB


6-speed manuals are already reaching top acceleration and top speeds in 5th gear, with the 6th gear for highway cruising. With 7 you'd either be adding a wasteful cruising gear, or making the low-end shift-points even closer together. Obviously we don't want the former; the later is only justifiable from a performance point of view if it increases gearing enough to offset the increased shifting. From a drivability point of view, it also makes the car more cumbersome to drive in stop-and-go traffic. And all of this has to take into account the increased cost of a 7-speed.
This is also the reason that the 3 series BMW are only 5 speeds, there is really no reason for a tall 6th gear.

http://www.rx8forum.com/showthread.php?s=&postid=14964#post14964

has information on the top speed for 1st - 3rd gears on the rx-8. Usnig that information, we can see that the gearing will be:

1st gear... approx 18.778
2nd gear.. approx 10.783
3rd gear... approx 7.134

The latest information from several sources (including the mazdausa site) also has the torque peak as being 159@5500 rpm. While we always knew that the middle lobe of the torque curve was approx 159@5500 , Mazda may be understating the hp and torque at 8500 because most people will appreciate a torque peak at 5500 rpm over one at 7500 rpm.

Using the new parameters in Cartest2000...

hp:........... 250 @ 8500
torque:.... 159 @ 5500
redline:.... 9000 rpm
wheels: ... 225/45R18

Diff - 4.1
1st - 4.58
2nd - 2.63
3rd - 1.74
4th - 1.33
5th - 1.00
6th - 0.80

curb weight:........ 2950 lbs
driver weight:..... 165 lbs
drag coeff:.......... .31 (conservative estimate)
grnd clearance:... 4.9" (estimated)
launch rpm: ........ 1600 (optimum est by cartest using all data)

Below are the some of the results:

0-60: ........... 5.73 seconds
1/4: ............. 14.4 @ 98.99 MPH
Top Speed: .. 156 mph

Brian

Below is a simplified way to calculate rear wheel torque. Get the total gearing ratio and multiply by the engine torque then subtract drivetrain losses (approx 20%).

Rx-8
1st - 4.58 * 4.1 = 18.778 * 159 = 2985.7 * .8 = 2388.6 ft-lbs
2nd - 2.63 * 4.1 = 10.783 * 159 = 1714.5 * .8 = 1371.6 ft-lbs
3rd - 1.74 * 4.1 = 7.134 * 159 = 1134.3 * .8 = 907.2 ft-lbs
4th - 1.33 * 4.1 = 5.45 * 159 = 866.6 * .8 = 693.3 ft-lbs
5th - 1.00 * 4.1 = 4.10 * 159 = 651.9 * .81 = 528.0 ft-lbs
6th - 0.80 * 4.1 = 3.28 * 159 = 521.5 * .8 = 417.2 ft-lbs

While the 3rd gen rx-7 had much more engine torque than the rx-8 will, we can see that it barely had more wheel torque than the rx-8 is estimated to have.

1994 Rx-7 twin-turbo
1st - 3.483 * 4.1 = 14.28 * 216 = 3084.48 * .8 = 2467.2 ft-lbs
2nd - 2.015 * 4.1 = 8.26 * 216 = 1784.16 * .8 = 1427.3 ft-lbs
3rd - 1.391 * 4.1 = 5.70 * 216 = 1231.2 * .8 = 984.9 ft-lbs
4th - 1.000 * 4.1 = 4.10 * 216 = 885.6 * .81 = 717.3 ft-lbs
5th - 0.719 * 4.1 = 2.95 * 216 = 637.2 * .8 = 509.8 ft-lbs

Rear wheel torque for 1st and 2nd gear on the rx-8 is estimated to be only 3% and 4% less than the 3rd gen rx-7. The rx-8 will hit it's top speed in 5th gear so 6th gear can be geared specifically for higher EPA highway fuel economy.

http://www.rx8forum.com/attachment.php?s=&postid=14970

That may be a little misleading.. you should take speed into account, and plot the difference over a given MPH range (not a given gear ratio range). You need to account for the fact that you might be able to be in a lower gear in the RX-7 at the same speed or that the torque curve could favor one over the other despite the gearing difference. I don't know how that would pan out, I haven't done the math. You seem to have some time on your hands, though :) In other words, make the same speed/torque graph for the RX-7 as you did for the RX-8 and overlay them. How much grunt available in a given gear is less important to the consumer than how much grunt is available at a given speed, me thinks.

Originally posted by Macabre
That may be a little misleading.. you should take speed into account, and plot the difference over a given MPH range (not a given gear ratio range). You need to account for the fact that you might be able to be in a lower gear in the RX-7 at the same speed or that the torque curve could favor one over the other despite the gearing difference. I don't know how that would pan out, I haven't done the math. You seem to have some time on your hands, though :) In other words, make the same speed/torque graph for the RX-7 as you did for the RX-8 and overlay them. How much grunt available in a given gear is less important to the consumer than how much grunt is available at a given speed, me thinks.
You are absolutely correct in that the 3rd gen rx-7 can stay in a lower gear through a higher speed range than the rx-8. The Rx-8 is geared approx 24% more but the redline is only approx 11% higher.

Of course the point wasn't to spend too much effort to analyze all of the performance differences between the 3rd gen rx-7 and the rx-8. I'm not trying to overstate the rx-8s case against the 3rd gen rx-7.

I believe the main concern that most people have is the relatively low torque peak of 159 ft-lbs. The point of the previous example was to illustrate that a car (which many of the readers here are familiar with) with 26% more engine torque does not necessarily have huge amounts of extra torque to the wheels.

There is no way the stock rx-8 can beat a stock 3rd gen rx-7 in a straight line because it is heavier, it still has less torque to the wheels and the rx-8 wheels/tires are bigger. For a practical 4-door sedan though, I would say it does a heck of a job trying though...

Brian

Hey guys,

As a current S2000 owner, I can add my impressions of the car. First off, the S2000 undergoes a gear reduction in the tranny before the final drive. In other words, at the end of the transmission, after the power has gone through the 6 speeds, and before it gets to the driveshaft, there is another reduction. Don't know the exact figure but I think it's around 10%.

The first time I rode in the car, after 5 minutes, my thoughts were "this car is geared too high". I still bought it, though, and I am still VERY unhappy with the gearing. It needs to be lower. The car is fine on a racetrack, but with all the power above 6k rpm, you come out of corners and stuff below the VTEC range. The aftermarket does make lower gears for the car (4.3, 4.44 and 4.77) so it can be fixed but I might just trade it in on an RX8.

The key reason why the RX8 will be a better street engine than the F20C is its powerband. It will be very linear, and have a lot of available torque in the mid range. Whereas I am always caught out in the S2000 at between 4-6k rpm (130lb/ft of torque here), the RX8 should have about 25lb/ft more in this range, and it will have a much more linear powerband.

Don't even get me started about the wimpy clutch or the weak rearend (Miata sized Torsen, not RX7 sized Torsen. :eek: )

Overall, I think that the Mazda will one-up the S2000 in terms of building a lightweight, hirevving sports car. I'm really looking forward to seeing the car at the Detroit Auto Show.

Anyways, just some food for thought.

Originally posted by Buger
http://www.rx8forum.com/showthread.php?s=&postid=14964#post14964

has information on the top speed for 1st - 3rd gears on the rx-8. Usnig that information, we can see that the gearing will be:


Oddly enough, I can't find the article with the speeds at 9000 anymore. I think the thread above was moved to a different section so the link doesn't work anymore?

How about another torque curve with the latest specs? The torque peak was lowered at 7500 so that the peak is now at 5500?

torque peak: ... 159
rev limit: ..... 10000
engine band: ... 9300 (10000 - 700)
95% or > tq: ... 44.1% (4100/9300)
90% or > tq: ... 61.3% (9000-3300 = 5700, 5700/9300)
80% or > tq: ... 86.0% (10000-2000 = 8000, 8000/9300)

Realize that this is still all speculation and all of the rx-8 torque curves that have been posted here have been derived from the torque curve found on the Swiss Mazda media site (http://media.mazda.ch/dossiers/Wankel/images/hi-res/skizze-05.jpg). That curve was first posted on the rx-8 forum by stan11003.

Buger, it's guys like you that I copied off of in math class in high school.;)

Could you compare your RX-8 numbers to the ones for the new Nissan 350Z?

I know that the RX-8 is going to out handle the Nissan, but I would like to see how they will compare in 0-60 and 1/4.

BTW, I'm in top of the list at my dealer (I already put moneydown), so I'm not a "Nissan troll".

Right now I have two cars, an Audi TT (APR, Borla, eibachs, 18” etc... but not room for my 1 year old baby) and a BMW 330i that my wife drives. She does not like to drive the TT, so I need a "sporty car” with room for my baby. I think that for the price the RX-8 is what I need. If the car is a disappointment then I'll have to spend 10k more and get the 330i Performance package (.5 seconds faster) that will go on sale early next year.

If anybody wants to buy a very fast, very good looking TT around March.... please let me know.


Alfonso in Austin

TT will sell for around 22K

Originally posted by Niebla
Could you compare your RX-8 numbers to the ones for the new Nissan 350Z?

I know that the RX-8 is going to out handle the Nissan, but I would like to see how they will compare in 0-60 and 1/4.

BTW, I'm in top of the list at my dealer (I already put moneydown), so I'm not a "Nissan troll".

Right now I have two cars, an Audi TT (APR, Borla, eibachs, 18” etc... but not room for my 1 year old baby) and a BMW 330i that my wife drives. She does not like to drive the TT, so I need a "sporty car” with room for my baby. I think that for the price the RX-8 is what I need. If the car is a disappointment then I'll have to spend 10k more and get the 330i Performance package (.5 seconds faster) that will go on sale early next year.

If anybody wants to buy a very fast, very good looking TT around March.... please let me know.


Alfonso in Austin

TT will sell for around 22K Isn't a "good looking TT" an oxymoron :D

Just kiddin with ya :)

Well.... this is a "better looking that normal" TT, the car has a sport suspension (lowered) and very nice 18" wheels.

To compensate with the cars "lossing the rear" problems that they had cornering at high speeds, I opted for getting pretty big tires in the back (even if the car is a not a rwd) so that will never be a problem.

The fronts are 225x40x18 (on 18x8'5) and the rears are 255x35x18 (on 18x10) RH Cup wheels. one more thing, the car is one of the first cars with the original "concept weight", so the car weight is only 2800 lbs, 4 months later the weight went up ...

If anybody interested I'll post some pics.

I'm not interested, but post the pics anyways. Show off for us. Make us envy you, and therefore bring yourself to a TIMELY end.
I'm just that bad.:D

Originally posted by Niebla
Well.... this is a "better looking that normal" TT, the car has a sport suspension (lowered) and very nice 18" wheels to compensate with the cars "lossing the rear" problems that they had cornering at high speeds

oh, i thought taht the reason for teh grip loss was aerodynamic, as the smooth sloping back would (does) create a lot of lift, hence the factory addition of the small spoiler... if you find this solution gives you better grip, hey cool, but wider tyres don't necessarily mean greater amounts of grip: it may even mean less. your car has some mass at any given time, yes?? that mass then needs a specific amount of normal force from the ground, and thus your tyres will get only as much normal force on the contact patches as the mass of your car causes (omitting downforce, 'cause nearly no street car produces any considerable amount of this... ya, i know about supercars, they don't count ;)), and thus only so much force will be applied to a specific area of rubber.
if you get wider tyres (ie. larger contact patch), you're then starting to spread that same amount of normal force over a larger area, then causing no net increase in grip, and decreasing the speed at which the rubber will heat (which, as i'm sure you know, is a major factor in tyre grip) up.

but again, if this solution worked for you, cool beans. :)

Wakeech, get on MSN.
Uhh.......I enjoy the RX-8....?

first off, you people are sick......i love it blahAHA

Second off lol, the wider tires increase grip because they create a larger area that the car is on to have a grippable amount of friction. The friction between the road and the tires of your car (ie the road and the tires rubbing together) is what you feel as GRIP

I always get the last word. PizzaflavouredRX8

god your sick, i love it blahAHAHA
________
Vaporizer Net (http://vaporizers.net)

Originally posted by P00Man
wider tires increase grip because they create a larger area that the car is on to have a grippable amount of friction.

welcome to the forum POOMan

well, what i was saying before was that this isn't necessarily true. the friction in this case is created (according to physical theory) by the ground pressing up on the tyre, which is exactly equal and opposite to the force of the vehicle presses on the ground (through the tyres). when you have a wider tyre, this force is distributed across a wider area, thus reducing it linearly as the area is increased. this linear decrease in force between the rubber and the ground creates then a similarly linear reduction in the "density" of the friction created by the tyres. what i mean is that the overall level of friction of the tyre is the same, but the specific amount of friction generated by some amount of area is reduced.

now, this can negatively affect grip as the level of adhesion a tyre has increases, to a point, with an increase in tempurature in the rubber of the tyre. the heat in the tyres comes from some some amount of rubber generating a specific amount of friction, translating the resistance to the lateral momentum of the car into heat (which heats the ground, the air, and the tyre). if the specific amount of friction an area of the tyre makes is reduced, the effective heating also is reduced, which will end up hurting grip (if the tempurature levels are below optimum).

sooooooo, long story short, more rubber means you need more force on them to get them to temp, and less rubber means it'll heat up higher, faster, and if there's not enough of it, blister.
in racing applications, where cars can use aerodynamically generated downforce, they can just add "weight" to their cars without adding "mass" allowing them to keep inertia low while heating really really big tyres to their optimum tempurature AND a whole lot of friction-producing "normal" force (force up from the ground), generating maximum grip.

the friction in this case is created (according to physical theory) by the ground pressing up on the tyre
Actually Wakeech, you're totally wrong. How can ground press up on something? Oh. Is it going to come up and smack it with a cane?
Is it the ground a pimp now?
Mr.SFU...disappointing.
when you have a wider tyre, this force is distributed across a wider area, thus reducing it linearly as the area is increased. this linear decrease in force between the rubber and the ground creates then a similarly linear reduction in the "density" of the friction created by the tyres. what i mean is that the overall level of friction of the tyre is the same, but the specific amount of friction generated by some amount of area is reduced.
What he's saying in the quote is, in actual fact. Blah blah blah blah blah. [Ben Stein Voice]
He discusses "linear reduction in the 'density' of the friction"
Well in actual fact there is no such thing as friction. Just a whole bunch of screwballs running around Surrey in a Toyota Echo.
sooooooo, long story short, more rubber means you need more force on them to get them to temp
Keech, what are you talking about. Tires don't run good at temp. You need COLD tires. Why do you think they have races in Northern China? Because they have Snow. People race as much as they can with cold tires. A common practise in F3000 is to get Liquid Nitrogen and pour it over the tires. Those babies are gonna last. And they give you a whole bunch of grip, because they become more denser than the concrete and they compact themselves onto it. They then thrust tiny particles of rubber into the concrete and create a line of force. Frozen tires ownZ j00.
And who says soooooooo anyway?
Keech, you really blew it this time.
TIMBER!

okay potatoehead, that's enough...
ROFL... jesus, change your name to Sarcastro or something, seriously...
please, don't get mad at him, he's just an idiot... ;)

I am just an idiot. But William Andrew, we've seen the pictures, drop the Chalupa.
And we all know the proper name for the so called FC is the FD:D

Don't anyone bother telling me I'm wrong. Cold tires own.
It says right here on my hand...wait a minute. It says up yours on it. Oh wrong hand. Right here, cold tires perform best. Go buy your Liquid Nitrogen today!

What's more annoying than listening to Keech yap?
Listening to Keeck say tire. TIRE TIRE!
NOT TYRE!

Well in actual fact there is no such thing as friction. Just a whole bunch of screwballs running around Surrey in a Toyota Echo.

thats pretty damn funny potatohead!! rotflmao:D and drop the chalupa :D

Originally posted by P00Man
Second off lol, the wider tires increase grip because they create a larger area that the car is on to have a grippable amount of friction. The friction between the road and the tires of your car (ie the road and the tires rubbing together) is what you feel as GRIP
Wider tires do not increase grip because they create a larger area/contact patch. Wider tires only CHANGE the shape of the contact patch, the actual area stays the same if you compared it to a narrower tire.

:D

Originally posted by Quick_lude
...Wider tires only CHANGE the shape of the contact patch, the actual area stays the same if you compared it to a narrower tire. That is completely incorrect. Wider tires at the same tire pressure do in fact have a larger contact patch.

---jps

I gotta agree with Quick_lude here...assuming equal inflation pressure for the smaller and larger tire.

Roughly 725 lbs to be supported by each tire (1/4 the car's weight) at an inflation pressure of 40 lbs per square inch gives a contact patch of a little over 18 square inches.

A wider tire gives you a wider, but less deep, contact patch. And better cornering grip.

Is not just the tire that is wider, the wheel went from a 17x7'1/2 to a 18x10. There is a 2 1/2 inch diference of contact surface before you start.....

I'm correct only if the overall diameter is set, so when doing plus 1 or plus 2 upgrades. Example, original whee/tire is 195/60/15, upgrade is 205/50/16. In this case "wider" tires don't mean larger contact patch, just different shape.
I'm sure a 305/35/18 tire has a larger patch than a 195/60/15.

Shear strength. If the tires were 185's on the rx-8, then when undergoing performance driving the tires would shred away to nothing.

So when the stock 225/45 18 reach their end of life, the replacements will probably be 235/40 18. This is a roughly a 1.5% smaller overall circumference. compared with 225/40 18 3.5% smaller than 225/45 18 (rough average from TireRack numbers).

I see that 235/40 18's 'want' an 8.5 inch width wheel, but if Audi can do it with the new S4 (4000lbs & 60/40 weight distribution) so can the Rx-8.(3000 lbs & 50/50)

bottomline, the rx-8 is gunna grip like a tank and speed like a bullet blahAHHA
________
NEW MEXICO MEDICAL MARIJUANA DISPENSARIES (http://newmexico.dispensaries.org/)

Originally posted by Quick_lude
I'm correct only if the overall diameter is set, so when doing plus 1 or plus 2 upgrades. Example, original whee/tire is 195/60/15, upgrade is 205/50/16. In this case "wider" tires don't mean larger contact patch, just different shape. How do you figure? A 205 is wider than a 195 (by 10mm), whether or not you're changing the sidewall height and/or wheel size.

That said, it's possible to get tires that are too wide for the car (especially in lighter cars). You spread out the low weight of the car over a large area of the tire, yielding little pressure on each square inch of the contact patch.

Originally posted by BryanH
it's possible to get tires that are too wide for the car (especially in lighter cars). You spread out the low weight of the car over a large area of the tire, yielding little pressure on each square inch of the contact patch.

<<cough>> thatswhatisaid <<cough cough>>

jeez, winter is sucky 'cause it makes me sick. :D

Oops. :o That's what I get for skimming some of the posts. ;)

Originally posted by Niebla
Could you compare your RX-8 numbers to the ones for the new Nissan 350Z?

I know that the RX-8 is going to out handle the Nissan, but I would like to see how they will compare in 0-60 and 1/4.

BTW, I'm in top of the list at my dealer (I already put moneydown), so I'm not a "Nissan troll".

Right now I have two cars, an Audi TT (APR, Borla, eibachs, 18” etc... but not room for my 1 year old baby) and a BMW 330i that my wife drives. She does not like to drive the TT, so I need a "sporty car” with room for my baby. I think that for the price the RX-8 is what I need. If the car is a disappointment then I'll have to spend 10k more and get the 330i Performance package (.5 seconds faster) that will go on sale early next year.

If anybody wants to buy a very fast, very good looking TT around March.... please let me know.

Alfonso in Austin

TT will sell for around 22K
Hi Niebla,

Sorry I didn't respond to your above sooner but I posted something comparing the 350z and rx-8 0-60 and 1/4 mile times at the following thread: http://rx8forum.com/showthread.php?threadid=1499

Brian

Ahh!
I got scared again by buger.

Any one see in the Car and Driver article where he (writer/test driver) hit 190kph/118 mph and said the engine was approaching peak power, was that in 4th or 5th gear?

Originally posted by ilovepotatos
Ahh!
I got scared again by buger.
I am hungry for Potato chips! :)

But I'm just a bunch of plastic and poly fibres!

Originally posted by MikeW
Any one see in the Car and Driver article where he (writer/test driver) hit 190kph/118 mph and said the engine was approaching peak power, was that in 4th or 5th gear?

With the gearing that I earlier estimated, 118 mph would be at approx 8350 rpm in 4th gear and 6250 rpm in 5th gear.

Originally posted by BryanH
That said, it's possible to get tires that are too wide for the car (especially in lighter cars). You spread out the low weight of the car over a large area of the tire, yielding little pressure on each square inch of the contact patch.

Contact patch size is a subject that many people disagree about. The below link does a pretty good job of explaining tire stuff: http://www.autospeed.com.au/A_0996/page1.html?src=suggestions

An excerpt is below:

"Myth 1: Wider tyres have a larger contact patch than narrow tyres

What actually influences the size of the tyre's contact patch? Is it the width of the tyre, or the profile? The simple answer that it is neither of these; the size of the tyre's contact patch is related to:

the weight on the wheel
the tyre pressure.

For example, say that the weight on the tyre was 900lb, and the tyre pressure was 10 psi. That internal pressure means that each square inch of area can support 10lb, so, in this case, the contact patch will be 90 square inches. If the tyre pressure was 30 psi, the contact area would be 30 square inches, and if the pressure was 90 psi, the contact area would be 10 square inches. This has been found to be almost exactly correct for most tyres (the exceptions being so-called run-flat tyres, or tyres with extremely stiff sidewalls). For most other tyres, carcass structure will have an effect, but by far the major factor is tyre pressure.

So, as you can see, the size of the contact patch of a tyre is not related to the width of the tyre - it is, in fact, proportional to the tyre pressure. What will change with the fitting of a wider tyre is the shape of the contact patch - it will get wider, but shorter longways."

buger i think that is what rich said in a similar thread months ago. i'll search later to see if i can find it. unless you beat me to it

here is what rich had to say

Not sure if this is what you're looking for, but...

To the best of my knowledge, there’s no “right” answer to many of your questions. I’ll start off with a few cold, hard facts that can’t (I don’t think…) be disputed. I’ll go into a bit of detail on things you say you already understand because I think the groundwork needs to be laid before we get into how things work in a particular application. This first post is basically wheels and tires 101. I’ll try to give some of my thoughts on your question in my next post.
Fact #1: Bigger tires do NOT have an inherently larger contact patch.
Many people think that bigger tires have a bigger contact patch. This is not true. The size of the contact patch is related to the pressure in the tire, the weight that is supported, and the strength of the sidewall. Let’s ignore the sidewall effect for a moment. The pressure in the tire is measured in pounds per square inch (or the metric equivalent, if you live in a civilized country). What does that pounds per square inch measurement really mean? If each tire is supporting ¼ of the 3000 lb. weight of the car, that’s 750 lbs. per tire. If the pressure in the tire is 30 lbs. per square inch, that’s 25 square inches of contact space. This does not change no matter what the size of the tire! If the tire is 6 inches wide, the contact patch will be a hair over 4 inches long. If you stick 12 inch wide tires on, the patch will be about 2 inches long (We’ll get more into this later). Stiff sidewalls can hold up a bit of the weight, so the contact patch will be less than is calculated here, but that is clearly a secondary effect. If that didn’t make sense, try this example. Picture an uninflated balloon. If you set it flat on a table, it will have a fairly large amount of surface area touching the table, because there’s very little pressure in the balloon. Now if you blow it up so that it’s really really full (lots of pressure), only a very small part of the balloon will be in contact with the table. Now, press down with your hand on the balloon. More of the balloon touches the table. You could use this balloon as a scale, if you wanted! All you’d need is the size of the part of the balloon that’s in contact with the table and the pressure in the balloon. Neat!
Fact #2: Unsprung weight is BAAAAD. Unsprung weight is the weight that is not supported by the springs of the suspension. This means everything from the tires, brakes and wheels up to the springs themselves, which are part sprung and part unsprung. It’s much more difficult to explain the physics of why this weight is bad, but I think an example works well. Imagine you’re driving in your car, and a wheel hits a bump. The job of the springs is let the wheel and tire move over the shape of the bump without jolting the car (upsetting its balance) or its occupants (upsetting their coffee). Shocks keep the springs from, well, springing. Left to themselves, the springs would just bounce and bounce and bounce. The shocks dampen this. Ok, what does this have to do with unsprung weight? The more weight the springs have to move, the slower and less effective they are. The more weight that gets moved by the springs, the harder a time the shocks have in settling the springs down. The less weight the springs have to deal with, the more effective they are at doing their job. Now, the sprung weight (everything supported by the springs) factors into this. If you’ve got a very heavy car, you can have beefy springs and shocks which can deal with the heavier unsprung weight better. This is why big wheels and tires have a huge effect on a Miata. Just an extra 7-8 lbs. in each wheel can make a Miata feel like it’s driving through molasses. The RX-8 is going to be about 500-700 lbs. heavier than the Miata, so unsprung weight will be less of an issue, but it’s still an issue. The ratio of unsprung weight to sprung weight is really the important thing.
An interesting aside – Why is it that many Miata drivers use very heavy tires for autocrossing? Simple, autocross courses are usually in a flat parking lot that’s swept before the race. In other words, they aren’t worried about taxing their springs and shocks with up-and-down movements. The stickiest tires are oftentimes heavy, and stick matters more in this context than weight.
Fact #3: Bigger tire circumference has the effect of changing the gearing to hurt acceleration and lowers cruising RPMs. This isn’t inherently bad, it just is. I’m not going to go into the gearing thing again (he hears a collective sigh of relief from the audience), but suffice it to say that if you keep everything the same and just change the wheels and tires, you’ll get more torque to the ground with a smaller rolling circumference than you will with a larger circumference. You will gain acceleration, but your engine will rev higher for any given speed. This isn’t usually a factor, since you screw up your speedometer and odometer if you go with wheels and tires that have a different sized circumference.

also here is the link (http://www.rx8forum.com/showthread.php?s=&threadid=531&highlight=balloon) to the thread if you want to read the whole thing. where is rich anyway?

Originally posted by Buger
So, as you can see, the size of the contact patch of a tyre is not related to the width of the tyre - it is, in fact, proportional to the tyre pressure. What will change with the fitting of a wider tyre is the shape of the contact patch - it will get wider, but shorter longways." Interesting. :) I know from personal experience that between identical tires with identical pressures, between 195/55/14 and 205/55/14 there is a noticeable difference -- the 205s have more grip. It's not in my head either, because I ran the car with the 195s up front and 205s in back, and the other way around, and also with 205s all around. Whichever end had the 205s on it had more grip.

I plan to jump to 225mm race tires next season.

Originally posted by BryanH
Interesting. :) I know from personal experience that between identical tires with identical pressures, between 195/55/14 and 205/55/14 there is a noticeable difference -- the 205s have more grip. It's not in my head either, because I ran the car with the 195s up front and 205s in back, and the other way around, and also with 205s all around. Whichever end had the 205s on it had more grip.

I plan to jump to 225mm race tires next season.
No one is arguing that wider tires don't provide more "grip" This is because the contact patch is now wider and shorter which helps in lateral grip.

Originally posted by Quick_lude
No one is arguing that wider tires don't provide more "grip".

well, it's not an empirical law that they do. i'm not going to repeat myself with all the luncheon meat i was cutting about how changing the area of contact doesn't affect the gross amount of friction created by a tyre, 'cause i've already said that. i've also already said a few things about tyre tempurature and how that's related to the amount of rubber one has on the road, and how that relates to grip.

just a question Bryan, were the tyres you were using exactly the same make, with the same amount of wear, of the same compound, contruction, and tread design?? if not, it's hard to validate your findings as true... i mean in the impirical sense, i'm not doubting whether those tyres you were using had more grip or not. if you say they did, then i trust they did. :)

ahhh!! post 666!! i've gotta do another one, quick!! ;)

hmmmm... one thing i've forgotten: how tyre pressure lends affects tyre tempurature...

For those of you who claim that the contact patch is merely "reshaped" on a wider tire, answer this:

If changing the tire patch so that it is wider is the only thing that makes handling better, then how come braking and launching also improves with wider tires?

Explain that.

---jps

Originally posted by wakeech
just a question Bryan, were the tyres you were using exactly the same make, with the same amount of wear, of the same compound, contruction, and tread design?? They were. :) Purchased at the same time in staggered sizes, otherwise identical.

Tread pattern? What tread pattern? :D
http://home.earthlink.net/~bryan64/pics/thunderhill/v700safter.jpg

Oh Bryan! By the way, I was biking home from work (Whoo hoo! Pizza Hut! Actually I'm not working much anymore, but thats beside the point)
I was biking along past the Bank of Montreal, and I hear this loud and unsettling fart. Now I think I've crapped my pants, but it was someone driving a black MR2 to the bank, very similar to yours! That guy had the worst aftermarket exhaust I've heard, (well 2nd worst, theres a guy at my school who took a Firefly Turbo and put a huge kit on his car, took it from 110 hp @ 3000 rpm to 110 hp @ 6000 rpm
:D
Anyhow, I think this must make you sad, to see a fellow MR2 owner (who was a girl by the way) go and take a quality set of wheels, and Crapify it...and who goes to Bank of Montreal anyways? That persons got their head on backwards.

Meh... rice happens. :)

Wow! I've got almost as many posts As Bryandog!

Ok everyone, here are the final rx-8 torque curves... :eek:

http://www.rx8club.com/attachment.php?attachmentid=625&stc=1&d=1315630388

so why does it appear to go up to 220 after your max torque point?

Final production gearing ratios for Japan (US to be same?)...

Diff - 4.444
1st - 3.760 * 4.444 = 16.7094
2nd - 2.269 * 4.444 = 10.0834
3rd - 1.539 * 4.444 = 6.83932
4th - 1.187 * 4.444 = 5.27503
5th - 1.000 * 4.444 = 4.44400
6th - 0.843 * 4.444 = 3.74629

Not quite as aggressive as the one article that mentioned speeds at redline for the first three gears but the gears are better spaced.

If the curb weight is 2920, Cartest estimates the below:

0-60......... - 5.99 sec
1/4 mile.... - 14.49 sec @ 100.68 mph
Top speed - 158 mph (if not speed limited)

Brian

Nice. Where does this graph come from?

Originally posted by zoom44
so why does it appear to go up to 220 after your max torque point?
That would be a good question to ask Mazda. I did not come up with these torque curves. It appears that the torque curve actually peaks at around 6000 rpm but perhaps Mazda marketing felt like a 5500 torque peak would "sound" better?

Buger,

Using your formula from a few pages back (3.760*4.444*159*.8), I get 2125 ft/lbs of wheel torque in 1st gear.

How does this compare with like g35 or 350z or s2000? I don't really know where to go to look up the numbers.

Originally posted by confucious
Buger,

Using your formula from a few pages back (3.760*4.444*159*.8), I get 2125 ft/lbs of wheel torque in 1st gear.

How does this compare with like g35 or 350z or s2000? I don't really know where to go to look up the numbers.

Hi Confucious,

Off the top of my head, the rx-8 will have more torque than the s2000 and less than the 350z and g35. This is expected as the 350z and the g35 are both several hundred pounds heavier .

Torque is good because it can accelerate a vehicle. But 300 ft-lbs wouldn't mean much if the car weighed 6000 pounds. What is a meaningful way of measuring what we are talking about?

I am at work now but I can graph something that really matters tomorrow morning when I'm home. A graph of accelerative G-forces throughout the rev range will take weight, gearing, powerband, etc into account and show you how the torque is really applied...

Brian

RX8

Diff - 4.444
1st - 3.760 * 4.444 = 16.7094 *159 *.8 = 2125/2920 = .736
2nd - 2.269 * 4.444 = 10.0834 *159 *.8 = 1283/2920 = .439
3rd - 1.539 * 4.444 = 6.83932 *159 *.8 = 870/2920 = .298
4th - 1.187 * 4.444 = 5.27503 *159 *.8 = 671/2920 = .230
5th - 1.000 * 4.444 = 4.44400 *159 *.8 = 565/2920 = .194
6th - 0.843 * 4.444 = 3.74629 *159 *.8 = 477/2920 = .163

S2000

Diff- 4.11

Gear Ratios

1st 3.13 *4.11 = 12.8643 * 153 * .8 = 1575/2790 = .564
2nd 2.05 *4.11 = 8.4255 * 153 * .8 = 1031/2790 = .370
3rd 1.48 *4.11 = 6.0828 * 153 * .8 = 745/2790 = .267
4th 1.16 *4.11 = 4.7676 * 153 * .8 = 584/2790 = .209
5th .97 *4.11 = 3.9867 * 153 * .8 = 488/2790 = .175
6th .81 *4.11 = 3.3291 * 153* .8 = 407/2790 = .146


The RX8 looks pretty good compared to the S2000 and is consistent with Buger's analysis using Cartest a few days back. Can anyone do an analysis of the EVO and STI?

remember torque in that curve is in newton meters which would have a lower ft-lbs torque.. im guessing 159 ft-lbs = 216 newton meters?

Originally posted by Buger
Final production gearing ratios for Japan (US to be same?)...

Diff - 4.444
1st - 3.760 * 4.444 = 16.7094
2nd - 2.269 * 4.444 = 10.0834
3rd - 1.539 * 4.444 = 6.83932
4th - 1.187 * 4.444 = 5.27503
5th - 1.000 * 4.444 = 4.44400
6th - 0.843 * 4.444 = 3.74629

Not quite as aggressive as the one article that mentioned speeds at redline for the first three gears but the gears are better spaced.

If the curb weight is 2920, Cartest estimates the below:

0-60......... - 5.99 sec
1/4 mile.... - 14.49 sec @ 100.68 mph
Top speed - 158 mph (if not speed limited)

Brian

Buger -- did you use the curb weight of 2920 in your calcs? I ask becuase if the car weighs in at 2920, actual race weight with driver and fuel will probably top 3120 lbs. And that may even be optimistic, since I've been hearing curb weight estimates in the 3K lb range.

Unfortunately, I don't see the RX8 breaking 100 mph in the 1/4, although I think it will be close. I suppose we'll know definitively within the next few months.

Even worse, I live in Colorado. Realistically, the RX-8 will be a high 15 second car up here, which is why I, maybe more than most people, desire a turbocharged RX-8.

Originally posted by Zio
remember torque in that curve is in newton meters which would have a lower ft-lbs torque.. im guessing 159 ft-lbs = 216 newton meters?

Hi Zio,

We are aware of the differences in the units used. Us Yankees always seem to need to look at things in our own way so we use hp and ft-lbs. :)

Brian

Many people have posted about the "lack of engine torque" that the rx-8 has. Indeed, many people who don't know any better will automatically think that their car will easily "beat" the rx-8 *simply* because they have more engine torque. Engine torque is just one of many factors though.

I previously mentioned that a graph of accelerative G-forces throughout the rev range will take weight, gearing, powerband, etc into account and show you how the torque is really applied...

Let's do a quick comparison of the Infiniti G35 5spd Auto and the Mazda RX-8 6-spd. I believe both will be priced around 27,000 US (G35 for this comparison is probably a little higher priced). I know that the g35 6 speed is a better performance comparison with the RX-8 but we will save that for later since I'm trying to illustrate how more torque doesn't always mean better acceleration here. ;)

The specs for the G35 are taken from http://www.infinitihelp.com/Infiniti/Models/G35/Specifications.htm.

G35
Price : Approx little more than 27,000 US
HP: ... 260 hp
Torque: 260 ft/lbs
weight: 3,336 Base (I used the lighter weight - G35 w/leather was listed as 33 lbs heavier for some reason)
Gearing: Diff - 3.357
........ 1st - 3.54
........ 2nd - 2.264
........ 3rd - 1.471
........ 4th - 1.000
........ 5th - 0.834
Wheels/Tires: P215/55R17 (Sport-Tuned suspension version)

RX-8 (Hi-Performance)
Price : Approx little less than 27,000 US
HP: ... 247 hp
Torque: 159 ft/lbs
weight: 2,920 (We've seen estimates under 2900 but 2920 is a reasonable estimate)
Gearing: Diff - 4.444
........ 1st - 3.76
........ 2nd - 2.269
........ 3rd - 1.645 <-- note that US has diff 3rd gear ratio than Japan
........ 4th - 1.187
........ 5th - 0.843
Wheels/Tires: P225/45R18

Just by glancing at the hp and torque specs, one might think that the G35 must be a lot faster. Taking the 400+ lbs of weight difference into account changes things. What about the gearing and tire size? Cars will accelerate based on their torque curves. Here's a comparison of the G35 and the RX-8 in first gear:


http://www.rx8club.com/attachment.php?attachmentid=663&stc=1&d=1315631652

Note that I used the production rx-8 torque curve. Cartest estimated the G35 curve based on the peak hp/tq figures.

You can see above that the 159 ft-lb rx-8 is estimated to have better acceleration than the 260 ft-lb g35 for the entire powerband in first gear. :eek:

260 ft-lbs of engine torque does not always accelerate faster than 159 ft-lbs of engine torque.

Brian

help me out here buger i'm tired. this means the rx8 pulls harder correct?
edit oops you alredy answered my question

Hi zoom44,

Yes. The g-forces are what you feel when you get pushed back in your seat. The harder you are pushed back, the more g-force you are feeling.

i know what g's are bug's i'm tired and the graphs are kind of fuzzy from my view. i need more caffeine. thanks for the posts though. keep knocking it into peoples head and between you and rich maybe they'll all get it eventualy

hey where can I find that cartest software???

I sure can use it to tune my cars in Gran Turismo 2 ;) :D

from the gearing numbers, looks like the low final gear ratio in the RX-8 (frigging 4.444!!!) is what makes the car pulls so strong :)

I havent used caartest in forever, but I do remeber it could make graphs of speed VS time. I always found those most usefull when bench racing. The g-forces in each gear are cool, but it only tells the tale of the tape in one gear. SO the RX8 will beat the g35 in first, what happens after that shift into second, or third.

What happens when the two cars meet on the road, and the mazda driver nails it from a lower rpm in 3rd rather than downshifting to 2nd? If the G35 leaves the line first, will the rx8 catch up? Is the rx8 going to be one of these engines that feels totaly slugish when it gets heat soaked a lil, like after sitting at a red light for a few minutes? Or is its performance going to be more depoendant on air temps than the g35? which car is going to be easier to launch? These are all things that cartest cant tell you, and will make a big difference in how this rotory is respected.

So in conclusion, if you wouldnt mind posting a speed vs. time graph, I think that will be more helpfull.

Originally posted by ZoomZoomH
hey where can I find that cartest software???

I sure can use it to tune my cars in Gran Turismo 2 ;) :D

from the gearing numbers, looks like the low final gear ratio in the RX-8 (frigging 4.444!!!) is what makes the car pulls so strong :)

Hi ZoomZoomH,

I originally found it by doing a google or yahoo search on cartest. I got the cartest2000 demo and paid 20 bucks or something to unlock the features that let me customize and add new cars to the database.

Brian

Buger-

Can you rerun your numbers through cartest with the 1.645 third gear that is on the North American 6-speed. I believe the numbers you previously posted used the Japanese 1.539 third gear.

How does this effect 0-60 times? I'm guessing that Mazda made this gear change for the US market since we're so hell-bent on 0-60 times.

Thanks,
Robert

No flames intended here, but am I supposed to be impressed by a 6 speed RX8 out accelerating an automatic G35? How about comparing the 6 speed RX8 to the 6 speed G35. Or better yet, compare the 6 speed RX8 to the 5 speed V6 _Altima_. Or the automatic RX8 to the Auto G35 or auto Altima. I think we will all see that those cars compare quite favorably to the RX8.

Plus, in terms of acceleration, Altima versus RX8, guess what. Better driver will probably win. Frankly, I think that's just sad. One of the mags recently tested the Altima at 5.99 seconds 0-60 and 97-99 mph in the 1/4. The New V6 Accord is also fast. 350Zs run the quarter at 102 mph. Maybe I'm wrong, but as I've said before, I don't see the RX8 bettering 100 mph in the 1/4. Need I even mention the $19,000 Neon SRT or the $33K SVT Mustang Cobra with it's built motor, six speed tranny, and fully independent suspension? Ugh.

My point is that the bar has been raised. Many cars these days offer a lot of power at a reasonable price. And I'm not even talking about "sports cars". An Altima for crying out loud? IMO, Mazda is just _barely_ keeping up with the competition in terms of acceleration. Maybe this is one reason why a number of individuals seem to be down on the RX8.

I realize that the original comparison was prepared by Buger to illustrate that low tq <> bad acceleration. It's not the lack of TQ that concerns me. It's the mediocre weight to hp ratio. And all the calcs in the world aren't going to change that fact.

With the RX8 you'd better think twice about who you're racing at the strip, especially if it's an Altima :(

anyone who thinks they can take a RX-8 or a S2000 to the quarter mile and expect to somehow dominate is a dumbass

Originally posted by infinitepat
I havent used caartest in forever, but I do remeber it could make graphs of speed VS time. I always found those most usefull when bench racing. The g-forces in each gear are cool, but it only tells the tale of the tape in one gear. SO the RX8 will beat the g35 in first, what happens after that shift into second, or third.

What happens when the two cars meet on the road, and the mazda driver nails it from a lower rpm in 3rd rather than downshifting to 2nd? If the G35 leaves the line first, will the rx8 catch up? Is the rx8 going to be one of these engines that feels totaly slugish when it gets heat soaked a lil, like after sitting at a red light for a few minutes? Or is its performance going to be more depoendant on air temps than the g35? which car is going to be easier to launch? These are all things that cartest cant tell you, and will make a big difference in how this rotory is respected.

So in conclusion, if you wouldnt mind posting a speed vs. time graph, I think that will be more helpfull.
Hi InfinitePat,

I wasn't trying to bag on the Infiniti. I think it is a very cool car but I wanted to post something about the "torque" issue since a lot of people are not informed about it.

I'm at work now but I'll probably post more stuff about this tomorrow morning. I ran the speed/time graph earlier this morning and from what I remember, the rx-8 was always ahead. A picture of the speed/time graph itself isn't very useful because you just see two diagonal jagged lines. I'll email you a jpg of it if you want.

It will be useful to post a g-force graph for more than 1 gear however. The acceleration of the G35 and RX-8 will not exactly match my earlier posted graph because of stuff like wheel slip, etc. I'll post a g-force graph of the 2 cars from approx 0 - 100 mph though. That would give a better indication of acceleration during every day driving. We should not be going faster than 100 on public roads yes?

Any car will not have as much torque in a higher gear than in a lower one. An Integra can probably beat a Testarossa from 20-50 if the Testarossa was in 5th gear. I'm not sure how much it would prove though. If you think that the rx-8 will be weak at lower rpms, you might want to look at a comparison of the RX-8 torque curve and the S2000 one. I think I'll post an overlay of the RX-8 and S2000 torque curves tomorrow too.

Of course there are many other things that need to be tested and felt while actually driving the car. Unfortunately the RX-8 isn't out yet and only a select few will get the chance to drive one in the next few months (Lucky Dan!).

Don't take this stuff too seriously, if your car doesn't end up faster
than the RX-8. There are many cars that the lower spec G35 can beat and there are many cars that will beat the RX-8. Be happy. :)

Brian

Originally posted by Rx4FUN
Buger-

Can you rerun your numbers through cartest with the 1.645 third gear that is on the North American 6-speed. I believe the numbers you previously posted used the Japanese 1.539 third gear.

How does this effect 0-60 times? I'm guessing that Mazda made this gear change for the US market since we're so hell-bent on 0-60 times.

Thanks,
Robert

Hi Robert,

You might not have noticed but I did use the 1.645 3rd gear in my last cartest thing. It doesn't affect the 0-60 times at all since 2nd gear will go a bit higher than 60 mph. It does affect the 1/4 mile time and speed a little bit though.

Brian

Originally posted by RedRX
No flames intended here, but am I supposed to be impressed by a 6 speed RX8 out accelerating an automatic G35? How about comparing the 6 speed RX8 to the 6 speed G35. Or better yet, compare the 6 speed RX8 to the 5 speed V6 _Altima_. Or the automatic RX8 to the Auto G35 or auto Altima. I think we will all see that those cars compare quite favorably to the RX8.

Plus, in terms of acceleration, Altima versus RX8, guess what. Better driver will probably win. Frankly, I think that's just sad. One of the mags recently tested the Altima at 5.99 seconds 0-60 and 97-99 mph in the 1/4. The New V6 Accord is also fast. 350Zs run the quarter at 102 mph. Maybe I'm wrong, but as I've said before, I don't see the RX8 bettering 100 mph in the 1/4. Need I even mention the $19,000 Neon SRT or the $33K SVT Mustang Cobra with it's built motor, six speed tranny, and fully independent suspension? Ugh.

My point is that the bar has been raised. Many cars these days offer a lot of power at a reasonable price. And I'm not even talking about "sports cars". An Altima for crying out loud? IMO, Mazda is just _barely_ keeping up with the competition in terms of acceleration. Maybe this is one reason why a number of individuals seem to be down on the RX8.

I realize that the original comparison was prepared by Buger to illustrate that low tq <> bad acceleration. It's not the lack of TQ that concerns me. It's the mediocre weight to hp ratio. And all the calcs in the world aren't going to change that fact.

With the RX8 you'd better think twice about who you're racing at the strip, especially if it's an Altima :(
Like I mentioned earlier, I wasn't trying to bag on the Infiniti. I think it is a very cool car but I wanted to post something about the "torque" issue since a lot of people are not informed about it.

A comparison with the 6-spd G35 would be more interesting and I'm sure you read the part of my post where I said I know that the g35 6 speed is a better performance comparison with the RX-8 but we will save that for later since I'm trying to illustrate how more torque doesn't always mean better acceleration here
A 5-speed Altima is another good comparison to do. Perhaps if any other people have Cartest2000, I can give you the customized RX-8 parameters that I am using and some other comparisons can be done a little quicker. I do have the time constraints of having work, family and other interests.

As it is, I wasn't trying to start a flame war about how this car is better than that or anything. I also wasn't trying to impress anybody that is already aware of the effects of weight, torque, gearing, tire size, etc. If straight line speed were the only variable in somebody's decision process, let's be clear that there are faster cars that can be had for less money. The Dodge Neon SRT immediately comes to mind if you want one.

The RX-8 will not get as much fanfare as the 350z but it will not really matter too much. I believe the 626 in it's worst year in the US still did a lot more volume than the 350z is going to ever do. Hopefully the next RX-7 does come along soon. Until it does, we shouldn't bag on the RX-8 for not being like it's older sibling.

Brian

Originally posted by ZoomZoomH
anyone who thinks they can take a RX-8 or a S2000 to the quarter mile and expect to somehow dominate is a dumbass

Good, so we're in agreement. The RX8's acceleration performance is mediocre.

Additionally, I don't recall saying anything about expecting the RX8 to "dominate" at the strip. I merely said that its acceleration performance is comparable to that of an Altima, which I think is unfortunate. I also implied that this fact may negatively impact people's perception of the RX8, and thus sales.

I think we all understand that the RX8 is not going to dominate at the strip.

I say we all relax and wait til the RX-8 comes. Only then we'll know what its capable of. Because right now all we're running off is speculation.:confused:

Originally posted by Buger

The RX-8 will not get as much fanfare as the 350z but it will not really matter too much. I believe the 626 in it's worst year in the US still did a lot more volume than the 350z is going to ever do. Hopefully the next RX-7 does come along soon. Until it does, we shouldn't bag on the RX-8 for not being like it's older sibling.


Brian -- yeah, I never intended to bag on the RX-8. I think it's an interesting car, to say the least. I will admit, however, that I am somewhat disappointed with it's straight-line performance, at least based on the assumptions I can make given the information that's currently available.

Unfotunately, acceleration metrics are important to US buyers -- maybe more important than they really should be. If that weren't true, we probably wouldn't be having a 9 page discussion about why lots of TQ isn't necessary for strong acceleration.

I do, however, realize that the RX-8, in ways, is more like the first and second gen RX7s than the thirds -- and that the first and second gens were actually popular and profitable cars for Mazda. So I definitely see merit in the design. It's just that, most likely, an MPS RX8 will better suit my tastes.

Originally posted by RedRX


Good, so we're in agreement. The RX8's acceleration performance is mediocre.

Additionally, I don't recall saying anything about expecting the RX8 to "dominate" at the strip. I merely said that its acceleration performance is comparable to that of an Altima, which I think is unfortunate. I also implied that this fact may negatively impact people's perception of the RX8, and thus sales.

I think we all understand that the RX8 is not going to dominate at the strip. I wouldn't say mediocre. It's up to par.

Look at the BMW 330. It's getting to 60 in 6 seconds AFTER Car and Driver tested it. It was released with a 0-60 time over 6 seconds from BMW.

My guess is that the RX-8 will reach 60 in 6 seconds from Mazda, and after it goes thru the paces with Car and Driver probably wind up at 5.8. Not too shabby.

Besides, and I've said this before, if you are going to take this car straight line racing and expect to win, yes, you are a freaking moron. 350Z will eat you for lunch.

However take the 350Z to the track and race it, you know.. the tracks with TURNS in them. Two equal drivers in each car... I'll put my money on the RX-8.

Using 804 revs per mile (Potenza S-03) for 225/45 18 tires and the US gearing

The estimated mph/rpm for shifting
1-2 40 mph/9000 rpms
2-3 67 mph/9050
3-4 95 mph/9350 US gearing// 100 mph/9150 Japanese
4-5 131mph/9250
5-6 151mph/9000
6 155 (250 kph) 7800

It looks like 3rd gear cold be 'extended' to 100 if you were able to rev to 9850 rpms. I wonder if that is for drag racing, 1/4:eek: perhaps;)

officially whats the rev limiter going to be? I know redline is at 9.

ZOOM ZOOM ZOOM! :p

I believe the fuel cuts off at 9500, so that should be it.

Boowana has said this engine will reliably spin to 12k, so I won't worry bout overrevving :)

Hey Buger, when you get your shiny new RX8 lets race! I live in Louisville up near Boulder. My torque apparently wont be doing much for me according to this thread, and my car being so much heavier than an RX8 should negate any horsepower advantage I might have! Oh goodie, this will be fun! I'll probably lose but it's not often I can keep up with Japan's latest and greatest http://forums.off-topic.net/images/smilies/fingersx.gif http://forums.off-topic.net/images/smilies/naughty.gifhttp://forums.off-topic.net/images/smilies/wavey.gif

3 things:

1) longest thread ever!
I think at 136 posts and counting we have a winner

2) There are way too many cars out there with way too much horsepower. It has indeed become a numbers game, much like someone made the great reference to the AMD vs Intel.

3) I build my own AMD machines, my parents buy Dells (Intel) and they both work great. Mine beats theres in some benchmarks even though the clock speed numbers would indicate it shouldn't. Their cpu wins in others.

4) ok 4 things. I went to Brown's Fairfax Mazda today in Fairfax, VA and gave them a non-refundable (but transferable - hi ebay) $1000 deposit for my sunlight silver with black/red $33,100:D stock number 0001 (their first order) I was told to expect it in by late june.

9500 fuel cut off I think I'm in love:D . I wish we had the compression ratios already.

:( I don't think 5.0THIS likes us

;) Can you say Apex?

Originally posted by rotisserie
9500 fuel cut off I think I'm in love:D . I wish we had the compression ratios already.

:( I don't think 5.0THIS likes us

;) Can you say Apex?

I'm just givin you guys shit, I have no problem with any of you :) I will race any of you with my Grand-Am! Muahahahahaah! :D

Originally posted by 5.0THIS


I'm just givin you guys shit, I have no problem with any of you :) I will race any of you with my Grand-Am! Muahahahahaah! :D Get on a real track with me and I'll school ya and that 5.0 :)

Torque won't mean much when your heavy boat is leaning side to side on each turn and the rear end slippage has no control because the suspension sucks...

Like they say, beauty lies in the eye of the beholder... even the beauty of the ride in the RX-8.

I drive a Pontiac too. :) Its a 97 Sunfire Gt. Sadly its the fastest thing I've ever driven. I love it though. But that is all gonna change in september :D

I think that the 330i 5 speed should be the benchmark for a 4 door sports sedan, so please do the graph etc of the 330i against the RX-8 that will give us a better idea.

Thanks for your hard work.

hahahahahahahahahahahhahahHAHAHAHAHHAHAHAHAHahhaha hahaahahahahahahahahahhaahhaahhahHAHAAHHAHAHAHAHAH AHAHAHAHAHAHAHAHAHAHAHAHAhahahhahahahahahAHHAHAHAH AAHAHahahahahah you gotta be kidding me HAHAHAHAHHAHHAHAHAHAHAHAHHAHAHAHAHAHAHAhAhAhAhAhAH AhAhAhAAHAHhAhHAaABHHAHAHAHAHAHahahahahahhahaah
________
Rhode island marijuana dispensary (http://rhodeisland.dispensaries.org/)

Originally posted by P00Man
hahahahahahahahahahahhahahHAHAHAHAHHAHAHAHAHahhaha hahaahahahahahahahahahhaahhaahhahHAHAAHHAHAHAHAHAH AHAHAHAHAHAHAHAHAHAHAHAHAhahahhahahahahahAHHAHAHAH AAHAHahahahahah you gotta be kidding me HAHAHAHAHHAHHAHAHAHAHAHAHHAHAHAHAHAHAHAhAhAhAhAhAH AhAhAhAAHAHhAhHAaABHHAHAHAHAHAHahahahahahhahaah
Please stop wasting bandwith with such nosensical posts.. at least tell us what/whom you are laughing at.. sheesh..

Originally posted by Hercules
Get on a real track with me and I'll school ya and that 5.0 :)

Torque won't mean much when your heavy boat is leaning side to side on each turn and the rear end slippage has no control because the suspension sucks...

Like they say, beauty lies in the eye of the beholder... even the beauty of the ride in the RX-8.

Guess again bud.... I dont own a 5.0, perhaps one of their competitors you'd say. And BTW, name the track bud! I have 3 years road course racing experience, and currently race oval track. Hope you're quick in the turns if you're gonna be schooling me around the track. My car only dynoes 291rwhp, 330rwtq, (about 335 flywheel hp, 385 flywheel torque) so I'm sure your RX8 far outpowers me!

what car do you have 5.0THIS? And do you guys think we're gonna get strong aftermarket support for modding our cars?

Originally posted by RedRX
Unfotunately, acceleration metrics are important to US buyers -- maybe more important than they really should be. If that weren't true, we probably wouldn't be having a 9 page discussion about why lots of TQ isn't necessary for strong acceleration.

Hi RedRX,

You are absolutely right that acceleration metrics probably plays an overly important part in US buyers decisions. One of the main reasons is the (relatively) cheap gas that we pay compared to the rest of the world. The Nissan VQ engine is a great engine and Nissan is smart to use it in as many vehicles as they can.

Car performance is more than just acceleration though. Assuming that people start their cars when they aren't moving and turn their cars off when they aren't moving, we can see that braking is just as important as acceleration. It is probably more important because better braking will save from an accident more than better acceleration. Any Miata owner can probably tell you about handling performance counts as well. A quick comparison of the 350z and the RX-8 performance?

Acceleration: . 350z
Braking: ........ RX-8
Handling: ...... RX-8

The bracing of the "freestyle" doors added a lot of weight to the RX-8 so the acceleration will not match the 350z. An Altima might have acceleration similar to the RX-8 but has nowhere near the braking and handling performance.

Insurance ratings for the RX-8 should be great too because of the 4 doors, great preliminary crash results, airbags, DSC, etc.

Brian

Originally posted by 5.0THIS
Hey Buger, when you get your shiny new RX8 lets race! I live in Louisville up near Boulder. My torque apparently wont be doing much for me according to this thread, and my car being so much heavier than an RX8 should negate any horsepower advantage I might have! Oh goodie, this will be fun! I'll probably lose but it's not often I can keep up with Japan's latest and greatest

Hi 5.0THIS,

I'm not a racer guy and I won't have my RX-8 for awhile since I'm trying to hold out for S-plan pricing.

If you have a 5.0, then you must be talking about straight line performance? ;) If you are talking about handling/autox stuff, you should try driving an RX-8 or Miata. Acceleration : price ratio is the Mustangs forte (since the camaros are gone at least ;) ) and handling : price is more of Mazda's forte.

Brian

Originally posted by 5.0THIS
Guess again bud.... I dont own a 5.0, perhaps one of their competitors you'd say. And BTW, name the track bud! I have 3 years road course racing experience, and currently race oval track. Hope you're quick in the turns if you're gonna be schooling me around the track. My car only dynoes 291rwhp, 330rwtq, (about 335 flywheel hp, 385 flywheel torque) so I'm sure your RX8 far outpowers me!

I would come and watch you guys if you do some autox thing close to here. :) How much have you put into your car 5.0THIS?

Brian

I'll post a g-force graph of the 2 cars from approx 0 - 100 mph though. That would give a better indication of acceleration during every day driving. We should not be going faster than 100 on public roads yes?

InfinitePat wanted more info that first gear. The below graph is from about 0 - 100 mph and takes tire slippage into account too.

How about Velocity Vs. Time Graphs?

Based on the dyno numbers that 5.0This is listing, I'm guessin' he's got an LS1 under the hood. So that means a Vette, Camaro, or Firebird. If he had a Vette, I would think his dyno would have been a bit higher, so I'm guessing he's got an F-Body.

I too have an F-Body. A '98 Z-28 Convertible. It's not stock and is putting down about 320HP at the rear wheels. But I'm still looking at the RX-8. And why you may ask?

'Cause horsepower isn't everything! I've upgraded the suspension and it corners fairly well, for a car that weights over 3600 lbs. But the car just isn't any fun to drive if you are on anything but a straight and smooth stretch of pavement. (Or your just cruisin' with the top down.) Throw in a curve or a bump and you really have to work to keep the car composed. I can powerslide with the best of them (on a track of coarse), but I wouldn't dare push the car to its limits on anything but a well prepared track because one bump, or divot, or patch of sand in the road and it's all over. The solid rear axle just isn't forgiving.

Now the RX-8 is a bit more like it. If I can shed 700+ lbs. get independent rear suspension(not to mention other handling goodies), seating for four (for those rare occasions), better styling(IMO)... I'd be willing to give up some of those ponies. Actually, quite a few ponies. The car would be so much more fun to drive. It would have enough composure at the limit that I'd push the car harder than my Z even though it had less power to do it with.

I haven't decided yet if I will sell the Z-28 when and if I get an RX-8... I may keep it around for those occasions when I just want to cruise with the top down. But I'd bet that if I keep both, the RX-8 would see a lot more miles!

~Robert

Originally posted by 5.0THIS


I'm just givin you guys shit, I have no problem with any of you :) I will race any of you with my Grand-Am! Muahahahahaah! :D

A Trans-Am is probably what he thinks he has, but considering he called it a Grand-Am, he obviously has no idea what he is talking about. Bring your Grand-Am to the track, leave your Trans-Am at home and the Rx-8 will run laps around the Grand-Am.

Are you even old enough to drive? Do you have a car? Get your story straight.:p

I think I'll post an overlay of the RX-8 and S2000 torque curves tomorrow too.

I tried to be a little optimistic when making the s2000 curve in cartest. The s2000 has an incredible engine but there is an engine that is smaller, lighter, and produces more power and torque throughout the rev range... :eek: :eek:

RX-8
torque peak: ... 159 ft-lbs
redline: ....... 9000
engine band: ... 8300 (9000 - 700)
95% or > tq: ... 43.4% (8400-4800 = 3700, 3600/8300)
90% or > tq: ... 59.0% (8900-4000 = 4900, 4900/8300)
80% or > tq: ... 83.1% (9000-2100 = 6900, 6900/8300)

s2000
torque peak: ... 153 ft-lbs
redline: ....... 8900?
engine band: ... 8200 (8900 - 700)
95% or > tq: ... 30.5% (8600-6100 = 2500, 2500/8200)
90% or > tq: ... 41.1% (8900-5500 = 3400, 3400/8200)
80% or > tq: ... 80.5% (8900-2300 = 6600, 6600/8200)

I have a feeling that somebody may try putting a renesis in a s2000 sometime in the future... :)

Brian

buger you da man!

good cartest software usage!

Thanks ZoomZoomH,

I'll try to do a comparison of some other cars tomorrow. I think I remember reading that people wanted to see how Altimas, 330is, 350zs and 6-spd G35 would do in a "bench race" for whatever it's worth. :)

It's too bad that out of handling, braking and performance, people want to always compare the weakest performance metric of the RX-8 to other cars. :(

Brian

Originally posted by Buger


I would come and watch you guys if you do some autox thing close to here. :) How much have you put into your car 5.0THIS?

Brian

Hey man, I was just kiddin with ya earlier. RX4fun was close, I do have a camaro, but it's just an LT1. I've only got some bolt ons, maybe 1500$ or so in stuff that gives it more power, no internal motor work, no blower, no bottle. I myself have not autocrossed before, but have many friends that do in the denver metro area. We'll have to meet up sometime if you want to get feel for the motorsports scene in Denver :)

RX4fun: interesting you should say a vette should have higher dyno numbers.... not necessarily. The engines are essentially the same, despite GM attempting to rate them differently. but the vette has to go through the Getrag transaxle, which soaks up more power than the live axle in the f-bodies, so in many cases the f-bodies put down more power, although they still arent faster because they weigh more.

pmacwill: I have a camaro, not a grand am. I was messing with you guys, apparently some of you are way too easy to get to! I apparently have no idea what I'm talking about. I admit freely that an RX-8 will handle better than an f-body, but 99% of people cant take any car to it's limits. I know how to drive my car, I've been racing for years, 3 years road course racing, and currently race in NASCAR's Weekly Racing Series (let me know if you want me to post a pic of me and my racecar). Exactly how much racing experience do you have? I'll bet if a grand am had equal power to an RX-8 I could run rings around you even with you in an RX8 :) In fact you pick the track... dragstrip, road course, autocross, whatever, and I'll bet you money my camaro could beat you in your RX8 at any venue! And yeah, I'm apparently old enough to drive, and I dont own A car, I own a few cars. Have a good day sir

Take it easy guys.

Andy

5.0This-

I know this isn't an F-body forum so I'll make this quick. The reason I said I didn't think you had a Corvette is because even a stock '97 or '98 Corvette will dyno at over 300rwhp. The stock intake and exhaust on an LS1 Vette are much more freeflowing and the vette motor doesn't have EGR. I agree that the LS1 F-body is underated by GM, but the stock vette does dyno about 10 rwhp higher. If you had a vette that was a 2001, 2, or 3, you should definitely be higher than the dyno numbers you posted.
As it is, you're numbers look pretty good for an LT1 with no internal mods or forced induction mods.

Everyone Else-
Speaking of drive train losses...I wonder what the drive train loss will be in the RX-8. The 6-speed RX-8 is using a composite one-piece drive shaft that is pretty short and 11 lbs lighter than the steel version in the automatic. Mazda also did a lot of work to make sure the tranny, drive shaft, and differential line up to reduce vibration. I would think these would add up to reductions in drive train loss as well. This could result in getting more power to the pavement.

I've heard rumors that the drive train loss on the 350Z is higher than people expected. (That is if the Nissan published HP numbers are accurate.)
It will be interesting to see how the actual RWHP numbers compare between these two cars. (Whoops, I forgot...HP isn't everthing...HP isn't everything...HP isn't everything. Sorry, I've just been a member of the F-Body world too long. There, HP is everything.)

~Robert

Originally posted by Buger


Hi RedRX,

You are absolutely right that acceleration metrics probably plays an overly important part in US buyers decisions. One of the main reasons is the (relatively) cheap gas that we pay compared to the rest of the world. The Nissan VQ engine is a great engine and Nissan is smart to use it in as many vehicles as they can.

Car performance is more than just acceleration though. Assuming that people start their cars when they aren't moving and turn their cars off when they aren't moving, we can see that braking is just as important as acceleration. It is probably more important because better braking will save from an accident more than better acceleration. Any Miata owner can probably tell you about handling performance counts as well. A quick comparison of the 350z and the RX-8 performance?

Acceleration: . 350z
Braking: ........ RX-8
Handling: ...... RX-8

The bracing of the "freestyle" doors added a lot of weight to the RX-8 so the acceleration will not match the 350z. An Altima might have acceleration similar to the RX-8 but has nowhere near the braking and handling performance.

Insurance ratings for the RX-8 should be great too because of the 4 doors, great preliminary crash results, airbags, DSC, etc.

Brian


I wonder just how much weight the freestyle doors and the related bracing added to this car? If this added a significant amount of weight, I think they made a huge mistake here. To sacrifice handling and performance for doors that still require the driver and passenger to get out first seems to be a questionable decision, at least for a sports/sporty car.

I eagerly await the true unveiling of the production model on the 17th at Laguna Seca.

Originally posted by Rx4FUN
5.0This-

I know this isn't an F-body forum so I'll make this quick. The reason I said I didn't think you had a Corvette is because even a stock '97 or '98 Corvette will dyno at over 300rwhp. The stock intake and exhaust on an LS1 Vette are much more freeflowing and the vette motor doesn't have EGR. I agree that the LS1 F-body is underated by GM, but the stock vette does dyno about 10 rwhp higher. If you had a vette that was a 2001, 2, or 3, you should definitely be higher than the dyno numbers you posted.
As it is, you're numbers look pretty good for an LT1 with no internal mods or forced induction mods.



Actually, many corvettes dyno below 300rwhp, even 6 speeds, it is actually quite common for 97-99s. The intake manifold on the vette is the same as f-body motors, and the manifolds are almost identical as well, however, after the manifolds the vette exhaust is indeed much better flowing than the f-body design.

5.0this - you know I was messin with you. I'm not a racer. I am going to use my car to get from point a to point b, and maybe to try to pick up some girls. thats about it. throw up a picture of the race car for kicks though, I'd like to see it.

cheers.

Yeah, lets see this bad boy. :D

Originally posted by pmacwill
5.0this - you know I was messin with you. I'm not a racer. I am going to use my car to get from point a to point b, and maybe to try to pick up some girls. thats about it. throw up a picture of the race car for kicks though, I'd like to see it.

cheers.

No problem man, I too was just messin with you :) I hope you have fun with your car whatever you want it for ;)

Well, I think it would be too big to just show it here, so here's the link to a pic of me and my racecar
http://www.bigwestracing.com/gallery/data/135ssandylewis24.JPG

And here's a pic of my weekend toy, my "grand am", and this pic might not be work safe for some of you :D

http://www.off-road.com/~sspickler/andy/girlsfront3.jpg
http://www.off-road.com/~sspickler/andy/side.jpg

great discussion/analysis buger ( and others)

we in the vw community are watching this car (and the Sti and evo-8 ) with interest :)

Thanks Scotty_Passat,

Hopefully we'll get more info this week after Dan gets to drive some of the pre-production RX-8s at Laguna Seca.

In the meanwhile, a couple of people wanted some speed vs time graphs. I did a more in-depth comparison of the 2003 s2000 and the RX-8. See some of the specs used below:

RX-8 (Hi-Performance)
Price : Approx 27,000 US
HP: ... 247 hp
Torque: 159 ft/lbs
weight: estimated 3,011? :(
Gearing: Diff - 4.444
........ 1st - 3.76
........ 2nd - 2.269
........ 3rd - 1.645 <-- note that US has diff 3rd gear ratio than Japan
........ 4th - 1.187
........ 5th - 1.00
........ 6th - 0.843
Wheels/Tires: 225/45R18
Diameter ......... 25.97"
Circumference .... 81.59"
Revolutions/mile . 776.52

2003 s2000 (from http://www.edmunds.com/new/2003/honda/s2000/2drroadster20l4cyl6m/specs.html?id=lin0018)
Price : Approx 33,000 US
HP: ... 240 hp
Torque: 153 ft/lbs
weight: estimated 2,809
Gearing: Diff - 4.1
........ 1st - 3.133
........ 2nd - 2.045
........ 3rd - 1.481
........ 4th - 1.161
........ 5th - 0.971
........ 6th - 0.811
Wheels/Tires: 225/50R16
Diameter ......... 24.86"
Circumference .... 78.09"
Revolutions/mile . 811.32

Although it appears the RX-8 is geared much shorter in every gear (multiply diff by gear ratio), it's wheels/tires have a bigger circumference. Because of this, the s2000 actually reaches it's redline at a lower speed in every gear except first.

RX-8 approx speeds at redline:
1st gear ... 42
2nd gear ... 69
3rd gear ... 96
4th gear ... 132
5th gear ... 157 but drag limited at approx 155
6th gear ... 186 but drag limited at approx 150

S2000 approx speeds at redline:
1st gear ... 42
2nd gear ... 65
3rd gear ... 91
4th gear ... 116
5th gear ... 139
6th gear ... 198 but drag limited at approx 147

The RX-8 could have had much faster acceleration if it were geared shorter. Many sports cars today are geared so that redline for second gear is reached right around 60 - 65 mph. This is done so that 0-60 figure which many people find so important will be higher. Mazda took a different approach for the RX-8 spreading the gears out so that top speed is reached in 5th gear and 6th gear is specifically for better fuel economy.

Below are graphs of the comparison. The Edmunds page has the 2003 s2000 0-60 time at 6.1 seconds. Cartest estimated the 2809 lb s2000 a little higher at 6.18:

http://www.rx8club.com/attachment.php?attachmentid=732&stc=1&d=1315631422

Buger, can you make one for the quarter mile please?:D

How about a 3D graph

X= Time
Y= Distance
Z= Velocity (Speed)


Kick Ass Graphs!

If is possible to change the gearing ratios, how much do you think that it will cost and what the gain could be.

Thanks

The graphs show that both cars will be very similar, despite the fact that some have claimed that the RX8 will be able to easily outperform the S2000. And I looked at a few S2000 dynos this weekend and they show at least 85% of max torque from ~3000rpm and up, compared to the claimed 90% on the RX8. It doesn't seem that much different to me, so I'm still looking for the graphs that maybe some people have seen that show the RX8 curve to be way better. Any links?

Originally posted by Buger
RX-8 approx speeds at redline:
1st gear ... 42
2nd gear ... 69

.....

The RX-8 could have had much faster acceleration if it were geared shorter. Many sports cars today are geared so that redline for second gear is reached right around 60 - 65 mph. This is done so that 0-60 figure which many people find so important will be higher. Mazda took a different approach for the RX-8 spreading the gears out so that top speed is reached in 5th gear and 6th gear is specifically for better fuel economy.

:(

Dang it! Mazda threw away one of the biggest benefits to a high revving/high RPM torque engine. You would see the benefit every time you drive with shorter gear ratios, but the longer gear ratios only give you the benefit of a tiny fuel economy increase, from what I can see. Couldn't they shorten 1st and second and end up at the same point for 6th as a fuel economy gear?

This is now my #1 question for Mazda, if I could have a conversation with one of them. If there's anyone here who might have the opportunity to interview someone from Mazda, please ask why the gearing is as tall as it is!

Originally posted by nk_Rx8
The graphs show that both cars will be very similar, despite the fact that some have claimed that the RX8 will be able to easily outperform the S2000. And I looked at a few S2000 dynos this weekend and they show at least 85% of max torque from ~3000rpm and up, compared to the claimed 90% on the RX8. It doesn't seem that much different to me, so I'm still looking for the graphs that maybe some people have seen that show the RX8 curve to be way better. Any links?

Hi nk_RX8,

Who are the people that claimed that the RX-8 will be able to "easily outperform the S2000"? I don't remember reading any posts here that mentioned anything like that?

I posted some similar torque curve stuff on the Car&Driver forum a couple of months ago and found out that S2000 people are very sensitive about the "torque" issue (almost as much as RX-8 people might be! :) ) There were claims that the s2000 had a flatter torque curve than a LS1 Corvette and that the s2000 had 5400 rpms of 90% or greater torque!?!?! :eek:

Perhaps you haven't seen the RX-8 - S2000 torque curves overlayed in http://rx8forum.com/showthread.php?s=&postid=20339#post20339 ? You will notice that I was very conservative in my #s on the RX-8 torque curve. If you can't tell the difference in the engine torque curves by looking at that graph, then I may not be able to help you.

Nevertheless, the below post that I made on the Car&Driver forum that has some links and is pretty much on this topic and may help explain things further...

----------------------------------------------------------------------------

Originally posted by Wizard:
1. S2000's engine makes 90% of its torque from 3000 rpm to about 8400 rpm, that is about as wide torque curve as you're going to see. It is proven by the torque curves posted by Waldorf (at the crank) and by Zorro19 (at the wheels).


So the question is: Does the emperor have any clothes on or not? As I mentioned earlier, I have looked at many s2000 torque curves before. The one that Waldorf posted appears to be the same one at: http://www.autospeed.com/A_0911/page1.html. It even has the same name but unfortunately it is rather small. The curve that Zorro19s posted appears to be graphed from excel but unfortunately has no grid between 100 and 150 so it is a little difficult to determine where the 90% mark is.

Fortunately the s2000 has been out for awhile and there are many sites that have the stock s2000 torque curve.
These are from dynos and have tick marks that make it easy to determine the values:

http://www.dynospotracing.com/s2000.htm
peak wheel torque: ... 137.5 ft-lbs
90% of peak: ......... 123.75 ft-lbs
range above 90%: ..... 5800 to 8600 = 2800 rpms or 31%

http://www.flyinmiata.com/tech/dyno_runs/FM99TvsS2000.pdf
peak wheel torque: ... 139.0 ft-lbs
90% of peak: ......... 125.1 ft-lbs
range above 90%: ..... 6200 to 8600 = 2400 rpms or 27%

This one is a rather small graph of the engine torque but it does have tick marks that make it easier to determine the values:

http://www.cartoday.com/content/technical/jake_venter/2000/power_torque3.asp
peak engine torque: ... 208.0 Nm
90% of peak: ......... 187.2 Nm
range above 90%: ..... 5800 to 8600 = 2800 rpms or 31%

Was I a little generous to the s2000 with my earlier estimates? Perhaps only a small one, unencumbered by bias or a fear of the Emperor, can see that 5400 rpms of 90% or greater torque might be a little exaggerated. Seriously, you love getting pushed back in your seat around 5500 rpms right? That is where your s2000 is starting to enter it's powerband.

And 90% of torque from every engine isn't a comparable number. Had the S2000 engine made 140 lb.-ft at its peak and 100% of the peak torque from 3000 to 8500 rpm, it wouldn't be the same as making 90% of peak torque with a higher torque output.

Quite a ridiculous example but what s2000 owner would care about a flat torque curve? ;) Just joking of course but if it could be geared about 10% more... I would imagine that first gear would go by too quickly. After that the driveability would be incredible. There wouldn't be the same top end "peak" that would be made peakier by the tighter gearing. Seriously though, you shouldn't think about lowering the torque of the s2000. :)

2. S2000 has enough revs to allow for a shorter gearing. There is a reason its short overall drive ratio allows for 44 mph in the first gear and 68 mph in the second. In fact, that is the idea behind getting more horses from the engine. To overcome the limit imposed by displacement in terms of torque output, more horsepower allowed short gearing. Ofcourse, it wouldn't be the car for them who intended a relaxed driver.

If you've read my earlier posts, you would know that I am aware of revs and gearing and I even stated that "The problem that many people have with the s2000 *shouldn't* be the peak torque of 153 ft-lbs. It is more than enough to move the 2800 lb s2000 very well". My problem with high gearing ratios on an engine that has a raised area in the upper 3rd of it's range is that it will make it seem even peakier than it is.

Perhaps some s2000 owners can't appreciate a powerband at low rpms because they have no use for it? Perhaps some people that have a powerband at low rpms can't appreciate a powerband at high rpms because they have no use for it? I don't agree with the trollish attitude the original poster of this thread had but there is something to be said for the driveability of cars with very wide powerbands. Not everyone is going to have the same views as you. If someone is closed minded and is only interested in ridiculing your view, just ignore them because your energy will be wasted on them. After saying that, I'm sure many people are tired of my rambling so I will exit this thread.

Brian
----------------------------------------------------------------------------

Originally posted by rotisserie
Buger, can you make one for the quarter mile please?:D

Hi Rotisserie,

I'll give the Cartest 0-60 and 1/4 mile RX-8 results for a variety of weights from 2950 - 3015 tomorrow morning.

Time to go to work now. :(

Brian

Originally posted by Niebla
If is possible to change the gearing ratios, how much do you think that it will cost and what the gain could be.

Thanks

Hi Niebla,

I'm not sure how much it would cost to change some of the gearing ratios or to change to a higher ratio rear diff. I'm sure that there are some crazy people here who have done that sort of thing to their cars before though. :)

Seriously, are 0-60 times that important to spend the money to do that?

Brian

Originally posted by Rich

:(

Dang it! Mazda threw away one of the biggest benefits to a high revving/high RPM torque engine. You would see the benefit every time you drive with shorter gear ratios, but the longer gear ratios only give you the benefit of a tiny fuel economy increase, from what I can see. Couldn't they shorten 1st and second and end up at the same point for 6th as a fuel economy gear?

This is now my #1 question for Mazda, if I could have a conversation with one of them. If there's anyone here who might have the opportunity to interview someone from Mazda, please ask why the gearing is as tall as it is!
Hi Rich,

I wish the gears were a bit shorter too but Mazda did say from the beginning that two of their main goals were to:

1. Disprove the rotary unreliability idea
2. Disprove the rotary fuel inefficient idea

If Mazda is looking toward the long term future of the rotary, these things may be more important than a couple of tenths of seconds. The production RX-8 may not perform quite as well as some of us were hoping but it will probably sell better to the masses because of some of the compromises. If Mazda can use the RX-8 to make some money and provide economies of scale to produce a new RX-7 for less money, it will be worth it.

Brian

I welcome the taller gear ratios. The car needs to be well rounded, not a drag racer. Buzzing along at high RPM at highway speeds on a long trip gets very old. Its not worth this hassle just to be able to say you can beat an S2000 or whatever. The appeal is the great handling, smooth gearbox, good acceleration and overall utility. If you want a racecar, mod it.

Thanks Buger! :)

I'm just hoping for Aftermarket Support:cool:

Buger,

I didn't mean to sound like I was dogging you or the RX8 because I wasn't intending to. I would much rather have an RX8 than as S2000 (I really don't like convertibles). But I just meant that I got the impression from reading in the forums that the RX8 definetely would have more mid range power than the S2000, especially since it seemed most people agreed that the RX8 has a broader, better torque curve. And from the previous overlay that you showed, that would seem to provide evidence for it. But your latest graphs seem to show that the two cars perform almost the same, or close enough that the difference is insignificant for me. I have ridden in an S2000 countless times, as a good friend of mine owns one, so I am using it as a benchmark in my head to compare against since we can't actually drive the RX8 yet. And I was hoping that the RX8 would feel like it had more 'pull' to it than the S2000, but so far on paper/graphs, it looks like it will feel the same. I like the way the S2000 drives, but I always felt like I wanted just another ~20-25ft/lbs of torque and it would be perfect. Some of what I want in a car may be provided for by the RX8's fatter midrange, but now the speculation is that it may way 200lbs more than an S2000 which kinda negates that. If the RX8 actually ends up being right at 2800lbs or less, than I think it's perfect for me.

I could easily be wrong about this since I haven't owned a rotary, but looking at the numbers for the S2000 and the RX-8 I am not sure what the advantage of the rotary is. The S2000 redlines at 9000rpm same as the RX-8, the torque and horsepower are similar, and I can't imagine the Renesis weighing much less than the 4cyl in the S2000. Can someone tell me why the RX-8 will be better with a rotary than with a 4 cylinder?

well, please don't forget that you're comparing the RENESIS to the most highly developed 4 cylinder engine in the world, which is terribly pricey, made by argueably the best 4 cylinder engine maker in the world.
Mazda is something of a David next to Honda's Goliath, and the rotary engine is a young (invented only in the 1950's) as a fundamental concept, so don't think for a second that these two engines are on the same level developmentally.

the first, and biggest reason, is that the RENESIS obviously has a higher specific, AND (more importantly) total output at peak and over a wider range, with its far flatter and more driveable torque curve. things like fuel efficiency, emissions cleanliness, are things i don't know about...
also, (certainly) the block of the RENESIS, with just the moving parts and stuff, i'm SURE is lighter and smaller than just the block and moving bits in the S2000 engine (isn't it the SA20 or something??)... some of those small displacement Honda engines are surprisingly big...
BUT, then again, these two engines should be compared with all the hardware that they need to work... as crate engines, i've got no idea which'd be smaller or lighter, but i certainly wouldn't be surprised to find out the RENESIS is both.

Originally posted by nk_Rx8
If the RX8 actually ends up being right at 2800lbs or less, than I think it's perfect for me.

seeing this car, with a 3011lb tentative mass coming from the two extra doors, two extra seats (with associated 12" in wheelbase), two more inches in hieght, a real trunk (10.5 cubic feet or something??) stay on par with a 200lb. lighter roadster, which gives up only 10 peak hp, should be nothing short of amazing. of course nothing would be better than to have a car which is magically lighter, but expecting anything south of 2900lbs. is really REALLY counting on too much, unless you're willing to take the base high-power and jettison a whole lot of stuff from the interior of the car.

Originally posted by wakeech


seeing this car, with a 3011lb tentative mass coming from the two extra doors, two extra seats (with associated 12" in wheelbase), two more inches in hieght, a real trunk (10.5 cubic feet or something??) stay on par with a 200lb. lighter roadster, which gives up only 10 peak hp, should be nothing short of amazing.

see if you wait long enough someone posts what you were thinking. thanks wakeech:D

welcome, rotary dog (?)

Hehehe, I keep scrolling down as soon as I see a bunch of numbers, or graphs in Bugers posts!

hahaha "set it and forget it" hahaha:D

Dear god. I'm frying in my own oil!

You may be right, but a man's gotta hope right?:) I'm just so hoping that this car is what I hoping for in a car. Both of my car buddies, knowing what I like in cars/driving, think that this car has my name written all over it and I guess I just have a lot of hopes. And what's great is that one of my buds who was dead set on a Z now has the RX8 as top of his list after listening to me for the past month.:D


Originally posted by wakeech


seeing this car, with a 3011lb tentative mass coming from the two extra doors, two extra seats (with associated 12" in wheelbase), two more inches in hieght, a real trunk (10.5 cubic feet or something??) stay on par with a 200lb. lighter roadster, which gives up only 10 peak hp, should be nothing short of amazing. of course nothing would be better than to have a car which is magically lighter, but expecting anything south of 2900lbs. is really REALLY counting on too much, unless you're willing to take the base high-power and jettison a whole lot of stuff from the interior of the car.

Originally posted by nk_Rx8
Buger,

I didn't mean to sound like I was dogging you or the RX8 because I wasn't intending to. I would much rather have an RX8 than as S2000 (I really don't like convertibles). But I just meant that I got the impression from reading in the forums that the RX8 definetely would have more mid range power than the S2000, especially since it seemed most people agreed that the RX8 has a broader, better torque curve. And from the previous overlay that you showed, that would seem to provide evidence for it. But your latest graphs seem to show that the two cars perform almost the same, or close enough that the difference is insignificant for me. I have ridden in an S2000 countless times, as a good friend of mine owns one, so I am using it as a benchmark in my head to compare against since we can't actually drive the RX8 yet. And I was hoping that the RX8 would feel like it had more 'pull' to it than the S2000, but so far on paper/graphs, it looks like it will feel the same. I like the way the S2000 drives, but I always felt like I wanted just another ~20-25ft/lbs of torque and it would be perfect. Some of what I want in a car may be provided for by the RX8's fatter midrange, but now the speculation is that it may way 200lbs more than an S2000 which kinda negates that. If the RX8 actually ends up being right at 2800lbs or less, than I think it's perfect for me.


Hi nk_Rx8,

You are correct in thinking that both cars will feel like they have similar amounts of "pull" when they are driven with the pedal to the metal and shifted at redline. The S2000's power is all in the upper range of it's rpms and shifting at redline will keep the engine in it's powerband very nicely. In everyday driving, people do not *always* shift at redline however. The great thing about the RX-8 is that you don't have to shift at redline to stay in it's powerband.

As an example, think about you in your [insert favorite color] RX-8 on a leisurely drive. You are in 2nd gear going about 43 mph @ 5600 rpm when you shift up to 3rd gear to cruise. At 42 mph in 3rd gear the renesis will be going about 4000 rpms and will still be well within the upper ranges of it's powerband. If you decide to stomp on the gas, you will still feel a nice amount of "pull" that keeps getting stronger as the torque curve increases till it's peak then basically stays there.

Let's say your friend was in his S2000 doing the same thing. He is in 2nd gear going about 43 mph @ 4900 rpm when he shifts up to 3rd gear to cruise. At 42 mph in 3rd gear the S2000 engine will be going about 3500 rpms and will be far from the upper cam of the S2000 engine where the real torque and power are made. If he decides to stomp on the gas, he will have to wait till his rpms raise from 3500 to around 5000 rpms before he starts to feel the significant pull of the S2000 on it's upper cam. Note that the S2000 torque curve stays the same or actually drops from 4000 to 4500 rpms.

This is where you will feel the difference in "pull". The RX-8 will have much more "pull" in the middle ranges of it's powerband than the S2000. Let your friend enjoy the performance of his S2000 while you enjoy the performance and practicality of your RX-8. Remember, he can only fit one girl in his car. :D

Brian

Originally posted by Fëakhelek
I could easily be wrong about this since I haven't owned a rotary, but looking at the numbers for the S2000 and the RX-8 I am not sure what the advantage of the rotary is. The S2000 redlines at 9000rpm same as the RX-8, the torque and horsepower are similar, and I can't imagine the Renesis weighing much less than the 4cyl in the S2000. Can someone tell me why the RX-8 will be better with a rotary than with a 4 cylinder?
Hi again Fëakhelek,

Off the top of my head, here are some reasons why to choose the renesis over the F20C (I think that is the name of the S2000 engine):

Higher redline .......... Renesis 9000 rpms vs F20C 8900 rpms
Higher hp ................ Renesis 247 hp vs F20C 240 hp
Higher torque .......... Renesis 159 ft-lbs vs F20C 153 ft-lbs
Wider powerband ..... However you want to measure it :)
Smoooother ............ Round & round not up & down
Lighter weight ......... Renesis approx 273 lbs vs F20C approx 310 lbs
Smaller size ............ don't know the figures off the top of my head :(

Why would a 4 cylinder be better than a rotary? :)

Brian

If the S2000 (and many other vehicles) has a "4 banger" then wouldn't the RX-8 have a "2 spinner"? :D

Originally posted by Buger

Hi again Fëakhelek,

Off the top of my head, here are some reasons why to choose the renesis over the F20C (I think that is the name of the S2000 engine):

Higher redline .......... Renesis 9000 rpms vs F20C 8900 rpms
Higher hp ................ Renesis 247 hp vs F20C 240 hp
Higher torque .......... Renesis 159 ft-lbs vs F20C 153 ft-lbs
Wider powerband ..... However you want to measure it :)
Smoooother ............ Round & round not up & down
Lighter weight ......... Renesis approx 273 lbs vs F20C approx 310 lbs
Smaller size ............ don't know the figures off the top of my head :(

Why would a 4 cylinder be better than a rotary? :)

Brian

Well, just to play devils advocate I can think of a few reasons.

1. Fuel Efficiency- Renesis 21/23 (est.) v F20C 20/28 [like it really makes a difference :D ]
2. Reliability- although theoretically the Renesis should be fine we won't really know for sure until 3+ years and 60,000+ miles from now
3. Dealer Mechanical Support- the number of Mazda mechanics with hands-on experience with a rotary engine will be very limited

Having said that the RX-8 is currently at the top of my list when I need to get a car with a back seat. I've been lurking around here since this site was put up (and at rotarynews before that) and am looking forward to test driving the car. As the former owner of a FB GSL and the current owner of a S2000, I think the primary advantage of a rotary over an I4 is the smoothness. I suspect the other factors will pretty much even out because of the 200lb (est.) weight difference. Anyway, very nice analysis of the engines and gearing of both vehicles.

If you look at the spec sheets, the quoted gas mileage is 24.4mpg, though I don't know if that's city, highway, or an average of both.

As per reliability, as long as you do your fluid changes on time there's nothing to worry about... the only thing that can go wrong is the apex seals cracking and that's solved by fluid changes, and the other thing that can happen is the rotor housing warping, and that's so unlikely it's not even funny :)

Trying to warp a cast iron block hehehehehe :)

Originally posted by Buger
I'll give the Cartest 0-60 and 1/4 mile RX-8 results for a variety of weights from 2950 - 3015 tomorrow morning.

I did some acceleration estimates for different weights using the US spec gearing ratios. This may give some idea of how the final weight will affect acceleration times.

SPECS:
hp: ............... 250 @ 8500
torque: ........... 159 @ 7500
redline: .......... 9000 rpm
wheels: ........... 225/45R18
driver weight: .... 165 lbs
fuel weight: ...... 30 lbs
drag coeff: ....... .30
Air temp: ......... 65 degrees F

curb weight:........ 2950 lbs :
0-60: ........... 6.03 seconds
1/4: ............. 14.48 @ 98.13 MPH

curb weight:........ 2975 lbs :
0-60: ........... 6.07 seconds
1/4: ............. 14.52 @ 97.92 MPH

curb weight:........ 3000 lbs :
0-60: ........... 6.11 seconds
1/4: ............. 14.56 @ 97.72 MPH

curb weight:........ 3025 lbs :
0-60: ........... 6.15 seconds
1/4: ............. 14.59 @ 97.54 MPH

Brian

Originally posted by cbj
Well, just to play devils advocate I can think of a few reasons.

1. Fuel Efficiency- Renesis 21/23 (est.) v F20C 20/28 [like it really makes a difference :D ]
2. Reliability- although theoretically the Renesis should be fine we won't really know for sure until 3+ years and 60,000+ miles from now
3. Dealer Mechanical Support- the number of Mazda mechanics with hands-on experience with a rotary engine will be very limited

Having said that the RX-8 is currently at the top of my list when I need to get a car with a back seat. I've been lurking around here since this site was put up (and at rotarynews before that) and am looking forward to test driving the car. As the former owner of a FB GSL and the current owner of a S2000, I think the primary advantage of a rotary over an I4 is the smoothness. I suspect the other factors will pretty much even out because of the 200lb (est.) weight difference. Anyway, very nice analysis of the engines and gearing of both vehicles.

Hi Cbj,

Thanks for the compliment. :) The S2000 is a production car so the EPA fuel economy figures can be seen at http://www.fueleconomy.gov/feg/compx2003f.jsp

1. The S2000 gets 20 mpg city / 26 mpg highway in the standardized test that the EPA uses for all cars. I previously estimated that the RX-8 will get 19 mpg city / 27 mpg highway which is a little higher than the 1.3L RX-7s from about 15 years ago had 17/25 EPA figures. The figures that the magazines put out have been wildly varying. We've heard as low as 20/24 to as high as 20/30 (from Car&Driver). It would be something if the RX-8 can beat the S2000 in fuel economy using lower compression ratios and a heavier car wouldn't it? :)

2. I'm not worried about the reliability issue although you are right that nobody will really know until the RX-8 has been out for awhile. One of Mazda's main goals was to erase the memory of the reliability problems of the last twin-turbo rotary. I think that is why they decided to go with a compression ratio of 10:1. A higher compression ratio would have increased power and fuel economy but perhaps Mazda will do this for a future model. By comparison, I think the S2000 has something like a 11.1:1 compression ratio. I've heard that BMW has had many problems with their M3 E46 engine (11.5:1 compression ratio) but I assume the S2000 has been quite reliable? (as Hondas usually are :) )

3. I think the dealer mechanical support is a valid concern. If something does go wrong, you want somebody who really knows what they're doing to work on it. There are many independent "rotary specialists" that are out there because of the demand for them though. Still, the RX-8 will probably have the same 4 year/50,000 mile warranty that Mazda is offering for their other cars so we will have to hope that Mazda makes sure that it's mechanics are competent with the rotary.

I think that many previous S2000 owners would be considering the RX-8. Do you agree? Most of us have to give in to practicality when we have a family and I would think that many S2000 owners would hate to go from their 8900 rpm revving car to some practical car that could only rev to 7500 or something. :)

Brian

Brian,

1. You're right on the 20/26 figure for the S2000. I don't know why 20/28 stuck in my head. I've seen the estimates for the RX-8 all over the board in the magazines as well.

2. Having owned a rotary before I'm not particularly worried about the reliability either. I do think Mazda will have to battle the rotaries= unreliable/inefficient perception some people have.

3. Dealer support is my only real concern. It's bad enough with an S2000 because some dealerships don't do much work on them, but at least it's still a piston engine. The learning curve for Mazda mechanics and the Renesis would be a little steeper. At least that is my gut reaction.

As for S2000 owners looking at the RX-8, I would thinkthere would be a fair number. It really depends on the person. If someone has to replace/add to the S2000 and really likes a good handling, high-reving, high involvement car - then it's a natural fit. Some folks end up wanting more luxury and the lower involvement of a higher torque engine and don't mind giving up a little in handing and adding a few pounds- they will probably end up with BMW 330/M3 or an Infiniti G35. Another group are those owners that might want something for the winter or prefer the upgradability of OEM FI and will look towards the Sti or the Evo.

The S2000 engine has been pretty reliable. There were some issues with a few of the early '99 cars. Also Honda just changed the design on the oil bolts and has done a recall for Europe but not for North America. The only thing I've had to do with mine was a recall for the spark plugs. The plugs were working loose on some cars so they changed the washers and the torque specs.

Most of the other problems with the motor seem to be caused by owner error. The predominate problem is overreving the engine by skipping gears when downshifting. i. e.5 to 2 at 80mph.

Originally posted by Buger
I did some acceleration estimates for different weights using the US spec gearing ratios. This may give some idea of how the final weight will affect acceleration times.

hp: ............... 250 @ 8500
torque: ........... 159 @ 7500
redline: .......... 9000 rpm Unless they've updated CarTest since I last tinkered with it, I think its results are likely to be a little conservative for the RX-8. If you can still only enter peak HP, peak torque and rev limit, there's no way to tell it about the flat torque curve of the Renesis. With just those three numbers to go on, I'll wager it extrapolates a curve that looks more like a VTEC Integra.

The flatter curve of the Renesis should result in less power drop between gears.

Originally posted by eccles
Unless they've updated CarTest since I last tinkered with it, I think its results are likely to be a little conservative for the RX-8. If you can still only enter peak HP, peak torque and rev limit, there's no way to tell it about the flat torque curve of the Renesis. With just those three numbers to go on, I'll wager it extrapolates a curve that looks more like a VTEC Integra.

The flatter curve of the Renesis should result in less power drop between gears.
Hi Eccles,

I used Cartest2000 which does allow you to enter specific parameters for customized torque curves. Both the RX-8 torque curve and the S2000 torque curve that I posted a picture of were from customized parameters that I created.

Of course Cartest2000 also uses profiles to create an approximation of torque curves based on peak hp, torque values adn redline if the specific curve isn't entered in. Their profiles actually do a very good job of estimating performance of the actual curves.

Brian

Originally posted by Buger


Hi Cbj,

Thanks for the compliment. :) The S2000 is a production car so the EPA fuel economy figures can be seen at http://www.fueleconomy.gov/feg/compx2003f.jsp

1. The S2000 gets 20 mpg city / 26 mpg highway in the standardized test that the EPA uses for all cars. I previously estimated that the RX-8 will get 19 mpg city / 27 mpg highway which is a little higher than the 1.3L RX-7s from about 15 years ago had 17/25 EPA figures. The figures that the magazines put out have been wildly varying. We've heard as low as 20/24 to as high as 20/30 (from Car&Driver). It would be something if the RX-8 can beat the S2000 in fuel economy using lower compression ratios and a heavier car wouldn't it? :)

2. I'm not worried about the reliability issue although you are right that nobody will really know until the RX-8 has been out for awhile. One of Mazda's main goals was to erase the memory of the reliability problems of the last twin-turbo rotary. I think that is why they decided to go with a compression ratio of 10:1. A higher compression ratio would have increased power and fuel economy but perhaps Mazda will do this for a future model. By comparison, I think the S2000 has something like a 11.1:1 compression ratio. I've heard that BMW has had many problems with their M3 E46 engine (11.5:1 compression ratio) but I assume the S2000 has been quite reliable? (as Hondas usually are :) )

3. I think the dealer mechanical support is a valid concern. If something does go wrong, you want somebody who really knows what they're doing to work on it. There are many independent "rotary specialists" that are out there because of the demand for them though. Still, the RX-8 will probably have the same 4 year/50,000 mile warranty that Mazda is offering for their other cars so we will have to hope that Mazda makes sure that it's mechanics are competent with the rotary.

I think that many previous S2000 owners would be considering the RX-8. Do you agree? Most of us have to give in to practicality when we have a family and I would think that many S2000 owners would hate to go from their 8900 rpm revving car to some practical car that could only rev to 7500 or something. :)

Brian

The EPA fuel economy estimates are often way off in the real world. A lot of the competing cars (with larger displacement engines/forced induction) with the S2000 have similar EPA estimates, but always seem to do much less in moderate/normal driving. For example, the Lancer Evolution has EPA estmates of 18/26 or 1 MPG combined city/highway less than an S2000. I seriously doubt that will hold true in the real world under NORMAL driving. I've seen many posts on s2ki.com with people getting 30 or more MPG on long trips doing moderate driving (not grandma driving!). Of course, some of these owners get like 7 MPG at the track.:D As for emissions, I remember Buger posted an interesting post about the renesis and the rx8s potential classification under current and new emissions rules. I think itd be interesting how the RX8 compares with some competing vehicles.

As for the reliability, I do think the Renesis will be fine, but I think it needs to build up a good reputation for people to percieve it as such. I think this will take some time and the F20C or similar engines should have the edge for awhile (at least in peoples perceptions).

I agree totally with the lack of rotary mechanics being a real concern. As someone who has had engine troubles far from home (in a pretty rural area), I think it is a valid point.

I think this is the 4th year of production for the S2000. I believe it is one of the last of the Honda's current models using the older generation of VTEC, but I could be wrong. I think all of their models (including the S2000 or some future performance car) are supposed to switch to I-VTEC.

The I-VTEC system offers better mid-range power than the VTEC system currently used in the S2000. I posted sometime back that the RSX-S torque curve was almost identical to the RX8's (albeit with only a peak of 142 lbs-ft with a redline of 7900). Obviously, this engine isn't tuned to to the level of the S2000 (they are both 2.0 liter 4 bangers). EVO magazine had a couple of articles about the RSX Type R (available only in Japan currently :( ) , which is about midway in terms of performance between the RSX-S and the S2000 (220 HP with a redline of 8500) and they seemed to indicate it had much more mid-range power than the integra type r (which was very similar in nature to the F20C). Ironically, they liked the ITR's split personality (i.e. high end power) better (even though the RSX-R put up better numbers)!

I think the Renesis and Honda's VTEC/I-VTEC or similar variant will lie within the best lightweight, low-moderately priced sports cars in the near future (say next 10 years). Though, I tend to think the Renesis has more potential for performance. I guess time will tell.

That's my Opinion, But You're Welcome To It!

Another thing regarding the S2000, I have always thought that convertibles tend to weigh more than coupes..and also tend to be an inferior design (as compared to coupes) for handling (less stiff suspension).

Oh, one other advantage to the F20C as opposed to the renesis, is it can be turbocharged...giving you mid 13s in the 1/4 mile. Though, I'd keep either engine naturally aspirited.

Originally posted by revhappy
...Oh, one other advantage to the F20C as opposed to the renesis, is it can be turbocharged...giving you mid 13s in the 1/4 mile. Sure, it can be turbocharged. Practically any engine can be turbocharged, even the Renesis. The resulting power is just a matter of tuning. But with it's high compression, sleeve-style or "open-deck" block (if I remember correctly), and lack of piston oil squirters (again, IIRC), it isn't built for, nor does it lend itself particularly well to turbocharging.

---jps

I did some acceleration estimates for different weights for the AUTOMATIC rx-8 using the US spec gearing ratios. This may give some idea of how the final weight will affect acceleration times.

SPECS:
hp: ............... 208 @ 7200
torque: ........... 164 @ 5000
redline: .......... 8000 rpm
wheels: ........... 225/45R18
driver weight: .... 165 lbs
fuel weight: ...... 30 lbs
drag coeff: ....... .30
Air temp: ......... 65 degrees F

curb weight:........ 2950 lbs :
0-60: ........... 7.02 seconds
1/4: ............. 15.19 @ 92.45 MPH

curb weight:........ 3000 lbs :
0-60: ........... 7.09 seconds
1/4: ............. 15.24 @ 92.16 MPH

curb weight:........ 3050 lbs :
0-60: ........... 7.17 seconds
1/4: ............. 15.31 @ 91.90 MPH

Brian

i know it's a lot, but take an hour and learn. :D

bump

What a fantastic thread... thanks all, especially buger.

How does the shift / drivetrain action compare between the RX8 and the S2000? This is important in any NA car.

The 8 you can into any gear at any time with great rapidity - which means you can really use the revs. I didn't drive an S2000 when I was looking because I just didn't like the cockpit or driving position, and I think I remember playing with the clutch and shift with the ignition off and going "urgh". Lots of people who've sat in the driver's side of my yellow fellow make remarks like "wow, you could really chuck this around".

why are the whts different on the 8's sold in Europe (11lbs) lighter

What a fantastic thread... thanks all, especially buger.

How does the shift / drivetrain action compare between the RX8 and the S2000? This is important in any NA car.

The 8 you can into any gear at any time with great rapidity - which means you can really use the revs. I didn't drive an S2000 when I was looking because I just didn't like the cockpit or driving position, and I think I remember playing with the clutch and shift with the ignition off and going "urgh". Lots of people who've sat in the driver's side of my yellow fellow make remarks like "wow, you could really chuck this around".

The S2000's shifter is significantly more precise and has shorter throws. The RX-8 is really good, but does not quite match Honda's shifter--it's more rubbery and has longer travel.