wakeech

...actually it's 10 chambers vs. 12... the 11 seconds isn't in the engine alone.

...haven't gotten off my lazy (metaphorical) *** and researched rule changes or changes in Mazda's racing program, staffing, partners, difference in weather conditions, track/racing circumstances, or anything like that yet... and hence am completely unconvinced that the rotary engine (which was banned the year following its victory, and slowly deregulated back in) is the big difference there.

rxeightr

This is the part of the RX-8 I am looking forward to exporing. I'm anxious to explore what power & mpg I get with normal commute driving, and then see the difference under aggresive useage.

I believe the RX-8 will satisfy my needs under both driving situations, which will truely make it a remarkable driving experience.

Skyline Maniac

I think rotary is an interesting technology, it functions like a automobile version of the motorcycle two stroke engine: High revving, gas/oil hungry, low torque, high horsepower, and relative simple design. To that extend, I'd say the rotary has more potential in small light cars and motorcycles.

You have to understand that Mazda holds the patent to rotary engine and they are not going to make this technology an open source. Imagine if a company like Honda gets a hold of rotary technology and builts one better than Mazda.... that would be the nightmare scenario for Mazda. Rotary will stay in the niche market because it is an exclusive technology, and applicable to a small number of specialized vehicles. Overall, rotary engines are more expansive to built (calculating R&D, manufacturing, parts sharing...) less confident inspiring, significant less torque and difficult to repair due to limited knowledge. To top it off, the general public were not very impressed by the reliability of the last rotary engine available on the market on the FDTT. (I know about the NA arguement, but most people wouldn't care)

wakeech

i'm gonna have to punch a bunch of holes in the stuff you're saying, but not to be a jerk

first off, the wankel motor is pretty thirsty fuel-wise, but it's a performance motor first: i'm not going to make excuses for that. the RENESIS has come a long way, but it's a performance motor first. the analogy between 2 and 4 stroke motors is, well, alright, but it's really like neither... in fact, i'd say it combines most of the best attributes from both, has a few unique advantages in itself, and but, i have a problem with saying that it's "oil thristy": this is just not correct. it does meter in a small amount of oil while the motor is running, which is purposefully burnt off as you know, but to say that its "thirsty" is a gross overstatement. the RENESIS is suppost to consume it at something like 1q / 10 000mi, which isn't half as bad as many normal econo-box engines as they get older, and consume oil as the ring seals weaken a little. its not a big cost issue, and something which has been refined a great deal too (from trickling down the carb to meter'd-direct-injection), and ought not to be a problem.

secondly, the wankel-type architecture has been fair game since the 60's. GM, Mercedes, and many, many, many-many others HAVE built (or at least tried to) rotary engines, and failed... to an upstart, know-nothing little Japanese car maker out of Hiroshima (3 guesses). Mercedes actually had a really rippin' 4 rotor, and GM made a rotary engine for the Corvette which never saw production, but it was Mazda that beat them all to it (by a lot) to get it to get it to work, get it into production, and get it to last.
now, of course anyone could again pick up the idea and try and build one better than Mazda, and i'd be all for it, but the problem is that Mazda has all the patents on all the right ideas, and is decades' worth of steps ahead of anyone else in terms of human capitol and patents on all the nifty stuff that makes the RENESIS the RENESIS.

lastly, yes, the wankel engine will probably always be a niche market engine, as a performance motor. this is because it's what the motor does best: burn tons of gas fast, in a small, light, and simple package... in fact, that's why i like it better than the piston engine: it's far better at it.
i'm lost as to why you say it's more expensive: the official statement from Mazda is that building the RENESIS, by hand, in its Ujina factory (or wherever) is cheaper (at least not more expensive) than building the V6's they put into their 6's. 'nuff said.

it is harder to find a guy who can tear down and rebuild your engine 150-200k miles down the road, if you wanna do that before it breaks itself, but its not like none exist anywhere. unless you live in the boonies (which i doubt anyone who's going to buy a $30k sports car is) there is one in the nearest urban centre. trust me, there is. aside from that, maintenance isn't rocket science. change the oil, filters, plugs, wires, coolant, misc lube, wipers... uhh... i mean, none of this stuff is different between a piston engined car and a wankel engined car. it's not that big a deal, or at least shouldn't be a deterrant to someone seriously considering the car.

the low torque comment... ouch. i know, i know, lets not all get into it, but for those who're new (welcome) you can tune a motor for low rpm operation, or high rpm operation. this is a performance motor, is only 1.3L in displacement, and revs to 9k rpm. it's a short stroke (10mm, yes, 10mm), "big bore" (it's really really oversquare) motor, yet makes 160lb/ft of torque. considering the last 13B made about 160hp at 7k rpm, and 140lb/ft of torque at 4k rpm, the RENESIS is a freakin' monster... no displacement increase, no big secrets. it's all in the side-ports. anyways, no, the geometry that Mazda has opted for isn't condusive to stump-pulling torque, but that's what revs are for :p.

the public may not have much confidence in the motor, but they will see, they will see. for 12 years the RX-7 reliably provided fun at a reasonable price, and only 3 model years of production won't completely erase that reputation Mazda has (with mucho credito for the Miata) for building good sports cars. in time we'll see, they'll see, everyone will see how this motor does.
sure, there'll be sh*t disturbers who claim to buy the car and storm onto the forum and just spout putrid things about whatever they can from every oriface, but they'll (hopefully) only be individuals. *shrug* now's the time to just wait and see.

revhappy

I agree with you wholeheartedly from a performance/racing perspective that the rotary is king. Pound for pound the piston engine can not produce nearly the same amount of power. You can produce the same amount of power (though less torque, but its not as big a deal on a racetrack) from a far smaller engine that gives you a lighter and better balanced car.

Unfortunately, in the real world fuel economy IS a limiting factor. There is the gas guzzler tax in the USA (that's ridiculously low at something like $1,000), but more importantly the CAFE standards. I think if they went with a significant increase in displacement on say the next RX7, I think that could be a concern (I know SUVs are currently measured on their own, but I thought I saw some proposed legislation that would include them with passenger vehicles, but I could be wrong). Of course, the average Joe who buys it could be concerned (as we are seeing with some people on the RX8). Maybe they can use a 1st to 4th shift like Chevy does on the vettes, but I personally just don't see a NA rotary with a large increase in displacement (unless there is a magic bullet breakthrough in fuel efficiency). An exotic with limited production could get away with that consumption, but i'm not sure about a $35-40K sports car? Thus in the real world where fuel consumption can not be absurdly below the competition, the NA rotary engined car will be at a power disadvantage (even on the track).

I think the only choice is to go with a super light car with a similar displacement to improve acceleration and keep fuel economy from becoming ridiculous compared to the competition. On the other hand, perhaps they can increase the compression ratio, but I'm not sure if they can do it and keep the engine reliable?

m477

Wrong. The RENESIS is smaller and lighter than the nearest piston equivalent, the F20C, but produces MORE torque. And more power. And gets better fuel economy.

Sure you could try to compare it to some big V-8 or whatever, but that's really apples to oranges...

Quote:

but I personally just don't see a NA rotary with a large increase in displacement (unless there is a magic bullet breakthrough in fuel efficiency).

There is. It's called less weight. A 2500lb RX-7 will have great (for a sports car) fuel economy, even with a 1.5 - 1.6 liter engine.

Also, a 1.6 liter Renesis even in the heavier RX-8 would still get about the same fuel economy as the 350z.

revhappy

I said an advantage of a rotary engine is that it can produce the same amount of power from a SMALLER displacement, but it will have less torque. The S2000 IMHO opinion is a lot closer to its theoretical maximum output than the renesis is so its really not an apples to apples comparison. Let's use the 2.6 L equivalent piston displacement (I know some argue for 3.9 L). If so, all other things being equal, you'd probobly have greater power from the rotary, but greater torque from the Piston engine (i'm sure it would not rev as high), but on a racetrack the rotary would be superior. However, this was not the point of the post.

QUOTE]Originally posted by m477


And gets better fuel economy. [/QUOTE]


The renesis does not getter better fuel ecomomy than the F20C (18/24 per EPA for the Renesis and 20/26 for the F20C). The F20C seems to do better than the EPA estimates in the real world (I have seen several owners on www.s2ki.come get over 30 mpg on the highway while I have not seen figures like that from Z owners - the Z has the same EPA estimates).


[/B][/QUOTE]

Well less weight certainly improves fuel economy, but I don't believe that the fuel consumption from an approximate 20% increase in displacement is going to be more than offset by that decrease in weight.

QUOTE]Originally posted by m477

Also, a 1.6 liter Renesis even in the heavier RX-8 would still get about the same fuel economy as the 350z. [/QUOTE]
[/B][/QUOTE]

Hmm...so this 1.6 liter renesis is going to get better fuel efficiency than the 1.3 L current version?? The Z already gets 10% better fuel economy!!!!

m477

Now you've gotten totally off track. The point was hp and torque PER POUND, not per liter. In which case the renesis beats the f20c at both. Also FWIW, SAE, whose job it is to set standards, considers the displacement of the renesis at 1.3 liters so your assumption that 2.6l is some sort of universal standard is flawed, but as I mentioned, displacement isn't relevant to the current discussion.

Quote:

The renesis does not getter better fuel ecomomy than the F20C (18/24 per EPA for the Renesis and 20/26 for the F20C)

Um, I thought it was 30mpg highway, at least that's what I've seen in every printed publication for the past several months.

revhappy

Yes, I agree with you that FOR ITS WEIGHT it should produce more power and torque (though both would not produce significant amounts at this displacement) than a piston engine of equivalent weight. The assumption of a 2.6L equivalent piston displacement comes from the folowing linked thread:

http://www.rx8forum.com/showthread.p...t&pagenumber=1

The bottom line is that the rotary is better from a racing standpoint in that you can produce more power from less weight.

However, the point of this post was to say that in the real world...the rotary's poor fuel efficiency limits its ability to compete with more fuel efficient piston competitors. Thus, its going to be at a power disadvantage with its competition as I think has been the case for the 1st and 2nd generation Rx7 and the RX8. A couple of ratios can make this point more clear:

Average EPA Fuel Economy/Road and Track's 0-60 and 1/4 mile times (higher numbers equal more efficient):
0-60 1/4 mile
350Z: 23/5.6 = 4.11 23/14.3 = 1.61
G35 Coupe= 23.5/6.1= 3.85 23.5/14.6 = 1.61
WRX 23.5/5.7 = 4.12 23.5/14.4 = 1.63
RSX-S 27.5/6.7 = 4.10 27.5/15.2 = 1.81
S2000 23/5.5 = 4.18 23/14.1 = 1.63
EVO = 22/5.1 = 4.31 22/13.5 = 1.63
RX8 = 21/5.9 = 3.56 21/14.5 = 1.45

Now someone can say well the renesis's poor fuel efficiency is offset by the superior handling and braking it yields:

As for the handling part, the OBJECTIVE scores do not reflect this:
R&T Slalom (MPH) R&T Skidpad (Gs)
350Z: 65.6 .89
G35 Coupe 67.7 .92
WRX 62.8 .84
RSX-S 66.8 .82
S2000 65.9 .90
EVO 68.7 .98
RX8 65.4 .88

As for the braking the RX8 does well, but let's see how well when we take its fuel efficiency into account:

Average EPA Fuel Efficiency/60-0 Ft. Braking Distance (higher numbers are more efficient)

350Z: 23/119 = .19
G35 Coupe= 23.5/117 = .20
WRX 23.5/138 = .17
RSX-S 27.5/146 = .19
S2000 23/123 = .19
EVO = 22/117 = .19
RX8 = 21/114 = .18

The point of this is that the renesis (at least as part of the RX8) is not as efficient (in terms of fuel consumption) as its piston competitors at producing power and performance. A higher performance version will likely have to solve this lingering rotary problem OR be a very lightweight vehicle without a significant increase in displacement.

Check out mazda's site and their own internal sales guide.

khoney

OK, this is way off-topic, but this thread made me wonder... where's Buger????!!!

chenpin

When you are "mag racing" you should take everything even the so call "objective test" with a grain of salt. Let's take a moment here and try to duplicate how a mag racer thinks.

R/T stats:
350Z: 65.6 .89
G35 Coupe 67.7 .92

wow, the G35c must handle much better then the 350Z.

C/D stats:
G35c 0.86 g
RX-8 0.91 g

can't find slalom from that article...but there is: "Its [RX-8] transient handling is similarly superior. [to G35c and Cobra]"

WOW! RX-8 must out handle G35c and the 350Z!.

Or all time my favorite stat:
Mclaren F1:
.86g
64.5 mph

[sarcastic]What a "crappy" handler![/sarcastic]

Unfortunately, many people actually do think like this. Now how do you reconcile R/T's .92g with C/D's .86g for the G35c? How do you reconcile the fact that R/T's stats state the G35c "handles better" than the RX-8 but C/D states otherwise?

I recommend reading up on the scientific method

revhappy

Whatever, I was showing that the benefits of the rotary (i.e. less weight, better balanced car) did not seem to outweigh its negatives (fuel efficiency). Yes there is variability in these figures due to a myriad of reasons (weather, driver, track, etc.), but using one source will limit that to some extent. Of course there will always be a few odd-ball figures in these handling tests, but that does not make them worthless.

They are a useful tool AS A SUPPLEMENT to subjective handling traits (i.e. steering feel, nimbleness, tossability, confidence inspiring, etc.). Unfortunately, subjective tests are not as easy to compare. Though, if you read between the lines , you will see subjective comments (or as Don would say "Damning with Faint Praise") about understeer, body roll and it being a poor autocross car (in stock form at least). So, I have yet to be convinced that the RX8 has "superior handling" compared to sports/performance cars, especially when taking fuel efficiency into account. Against most sports sedans, I would agree the handling should be better.

The central question is: does the benefits from the rotary (in this case: lighter weight and balance yielding better handling) outweigh its negatives (in this case: poor fuel efficiency)? From what I have seen it is no. Of course here we are putting equal weight on both, but I'm sure in the real world most would not put that much emphasis on fuel economy (well maybe in Europe). However, as a design (at least in the form of the RX8) it does not seem to produce as much performance as its piston competitors when fuel efficiency is considered.

Thus my main point is that if a rotary is not nearly as fuel efficient as its piston competitors, its going to have to sacrifice speed to keep the fuel economy difference from getting ridiculous (which is the case in the real world) UNLESS it is made super light (and lacks the amenities of its piston rivals). So, we are back to it being a niche engine.

Hercules

So then revhappy, let us 'nichers' enjoy the car for what it is.

You have your Evo right?

This topic is WAYY off now from what I started it out to be which is simple: Would the rotary engine be more efficient (in power or efficiency) had it been given the same amount of development time as piston engines.

I think the conclusion here is that had the rotary been given as much money and effort as piston engine, we'd have a far superior engine in EVERY way to the piston engine.

Only a handful of engineers over the last 20 or 30 years have developed a 1.3L wankel that gives out more power per liter than any car on the road today. Imagine if they had millions more and more brilliant minds working on it.

Hercules

Oh, one addendum though...

I fail to realize, and it has been debated thru this thread, what gas mileage has to do with inherent performance of an engine.

Are you buying a fuel miser car, or are you buying a sports car?

If you are buying any of the listed cars (350Z, G35 Coupe, etc) for fuel economy then you're buying them for an unintended (and probably poor choice) purpose. The goal of all these cars is to bring a grin on the face of the person who's driving.

I think that the low weight of the RX-8 (regardless of straight line power) will put a big grin on my face, similarly where you will love the power of the EVO. However being that I don't like AWD it was not a choice for me, and it would be the G35 Coupe that would compete for the RX-8's spot in my garage. On paper it seems the RX-8 would provide the driving experience I want in a car...

Anyways since I'm not a mod here, can we please get this topic either back on track, or split into a different one?

Cheers.

DonG35Miata

I think it would be much better than it is even in Renesis form, but in EVERY way, I am not so sure. Remember my wheel analogy- the basic design is fixed. The wankel is by nature a low-displacement, high-revving engine. This is at cross purposes with low-end torque and fuel efficiency- pretty much the only drawbacks of the engine, when you think about it!

I guess supercharging, etc could come in to play here, but in its raw form, I don't have the imagination to guess at what could make the engine more powerful or efficient.

wakeech

oh, yes, you could improve on it in every way. with application specific materials (which may, or may not be as utile in piston engines) the thermal losses from the giant surface area in the combustion chambers could be reduced greatly, helping to eliminate the cooler zones in the corners and edges where unburnt fuel goes to waste and eventually gets out and pollutes.

just 'cuase the geometry is fixed doesn't mean you couldn't screw around with the proportions to make a very large displacement, low revving, high compression motor (for diesel application or something)... big big rotors, that're very skinny could maybe get the compression ratio high enough (i've never figured the math, so i'm not sure)...
but you are very right about the fuel consumption being its only drawback... whereas again, i must contest this notion of low torque: it's not low torque. it's low in comparison to a very large, long stroking engine. it's actually pretty damned amazing when you line it up against straight fours, which are (in size-limited application) more similar... smaller, but as (or more) powerful than much larger engines, with the only drawback fuel consumption??? c'mon... it's not THAT bad... it's a couple mpg short of the S2000, which is a couple of bucks per week... sweat it out if you like, but i don't and won't care: gas is the cheapest part of owning a performance car.

as for how to "improve" the engine without resorting to forced induction, it's pretty simple: you can increase the force the engine makes per turn at some speed, or increase the speed at which it can make some amount of force: more rpms, more torque = more power.
to increase the amount of force the engine can make per turn, you have to improve the amount of air + petrol it can burn per turn, in amount (filling the volume as full as possible) and efficiency (losing as little energy as possible to pumping it in and out).

revhappy

Well, I still think fuel efficiency matters, even if you don't care about the gas costs. If fuel efficiency/emissions had NO impact, then I'm sure Mazda would make a larger engine (that would still be smaller than its piston counterparts) and let the thing suck gas and emit black clouds and end all of the talk about it being inferior in a straight line.

The bottom line is that fuel efficiency/emissions does matter in that it can't be ridiculous compared to the competition. Whether that is due to the individual consumer or goverment regulations, it doesn't really matter as the rotary's inefficiencies (in this regard) will put it at a competitive disadvantage. The metrics I posted clearly showed that the RX8 is inefficient (in regards to fuel consumption) at producing power and overall performance. Really, what it shows is that the car should be lighter to increase performance and improve fuel consumption.

Personally, fuel consumption IS a consideration for me, though secondary to performance. Its not due to cost, but I appreciate an efficient design and will encourage ones if I can. I think this is relevant to the discussion as it is one of the primary negatives of the rotary currently.

That being said, this engine has so much potential from a performance point of view. Really, if this problem was licked, I think the rotary would be the engine of choice for many sports cars. Maybe Mazda can hire Wakeech or Buger to work in R&D on this issue?

wakeech

...yeah, i just rememberd you have an EVO... what're your "real world" numbers that you're getting from your (obvious ) spirited driving??

...oops, another thread steer'd OT by your truly... oh well... :D

revhappy

Haven't got it yet. I'm on a waitlist for a garage in my apartment complex. It looks like 20-25 MPG is doable WHEN DRIVING REASONABLY based on this thread on evolutionm.net:

http://forums.evolutionm.net/showthr...g&pagenumber=1

Its really not bad when you consider its power, engine torque, weight, AWD and aggressive gearing.

Hercules

Well Mazda got the emissions problem of the rotary fixed... I'm sure as the development takes its turns, then we'll see better and better numbers from the estimates.

Besides, the *best* thing about the rotary, in preparation for the future.... is its ability to combust hydrogen fuels better than piston engines.

And with the Powerball technology emerging (and others like it) for the future, you'll have a nearly unlimited supply of fuel in your car. One load of powerballs, say 5 gallons worth, will give you about 400 miles at 10mpg.

No emissions either

Everything comes in time. From your own words, you support the economical design when you can. I'm supporting the design that will break the mold and *be* the future.

chenpin

You'd be surprised at the variations that can come from these test. Depending on variations in conditions, results can be quite different. Even small changes can have large effects. No, they are not worthless. By the test I can tell the Evo has better grip then an Accord. But if results are close then favorable conditions can easily put one car in front of another UNLESS they are tested at the same time. How many of those reviews are done at the same time? none (except real comparos)

JSG seems to be having no problems with steering feel, nimbleness, confidence, etc. Also, those reviews were done on PROTOTYPE CARS. In the recent Best Motoring video Gan-san states the handling on the production car has improves greatly. "Tires seem to grip better...helps its balance"

Isn't that obvious?

Oh, on our Evo8 we are getting ~18.5 mpg. Shifting~3k

revhappy

Well, I think you are exaggerating just a tad there. Road and Track lists variations of what it considers as immaterial as follows:

Slalom: 1 MPH
Skidpad: .02 G
MPG: .5 MPG

http://www.s2ki.com/forums/showthrea...hreadid=103564

Now, I don't know if those are statistically derived or not. Yes, there is variation between tests, but not many things in life are perfect. Clearly, a rational person can see a trend even if the exact figures aren't 100% perfect. I challenge you to find any one magazine that shows the RX8 getting better slalom and skidpad results (same magazine for both cars). The EPA tests are fairly standarized from what I know.



Well, I guess we'll see, but I'd be surprised if the changes are monumental since they were very close to production when those tests were done.



Not too shabby when you are only 500 RPM away from maximum torque of 273 lb-ft. in an AWD, aggressively geared car that can comfortably sit four. Still, I think your brother is cheating a bit.

chenpin

Car and Driver. RX-8 gets 0.91g while G35c gets 0.86g. Don't have slalom results but RX-8 beats it I think. Oh yeah, these test were done at the same time so....same facilities and same conditions. (unlike R/T which basically cut/paste info)

Yeah, it does kinda irk me that we will probably be getting ~same mpg but he will murdur me in a straight line. But then I just think, "Hey I can just drive his car when I feel the need for speed" :p He probably does cheat! :D

revhappy

I meant between the EVO and the RX8.


Yup, I'm just saying that the rotary's fuel inefficincies put it at a competitive disadvantage. Believe me, if this problem was solved once and for all you would see a lot of rotary powered sports cars.

chenpin

Duh! That's why I stated the "skidpad obviously can tell me an Evo has better grip than an Accord". Big differences are easily seen. If you read my original statement, I stated that if results are close then it would be hard to tell exactly which car is better due to varies inconsistencies. That's just one problem with these test.

Another problem is that these handling test often fail to deliver the "whole story". Case in point: Mclaren F1, .86g, 64.5 mph. The whole point is that you do not drive a spec. sheet. You drive a car, a highly complex machine that can't be described wholely by numbers. Doing that is a lot like....rating how much fun you have in bed by a woman's chest and dress size!

It really does. But I think that if the Renesis is any indication of Mazda's commitment, then we are in good hands. We'll just have to wait and see how well the RX-8 sells. Then we can continue this conversation.