I just put 640 miles on my car ('07 Sport MT) and ran my G-Tech pro (led version) for 3 runs.

I ran it ealier at about 400 miles and pulled consistant 175 hp. Air temp was around 50F. I entered just above 3600 pounds and I had a nearly empty tank (dealer gas).

Tonight at 640 miles I pulled a 199, 185, and 195. The air temp read 47F
I entered 3640 for my curb weight which is a guess since my tank was 3/4 full (Shell Gas).

I will do some more runs later this week. I need to get on a scale to see what the real weight is, but since I entered about the same amount each run, I don't see the weight being a major factor for increase in HP.

I feel pretty good about it.

weight is NOT a factor in how much horsepower is made. It CAN BE/IS a factor in how efficiently that power is delivered to the wheels though. there is a very nice thread somewhere around about sprung/unsprung weight, rotational masses, etc that explains in detail how that works

the testing should be done with 0 to 60 and .25 mile times..

and i got to tell you... if you are putting in 3600lbs.. you have 3 very fat riders... with a full tank of fuel...

beers :beer:

weight is NOT a factor in how much horsepower is made. It CAN BE/IS a factor in how efficiently that power is delivered to the wheels though. there is a very nice thread somewhere around about sprung/unsprung weight, rotational masses, etc that explains in detail how that works

With an accelerometer weight has everything to do with the net results. If my car accelerated at the same rate but weighed twice as much then I could expect to see higher HP numbers.

As for my weight I simply added to front and rear weight to arive at my total weight as seen from the door jam.

Like I said before, I will need to get on a scale to know the real weight of the car, along with my four other fat friends. I will try using 3000 pounds next time. With the lower weight I would expect to see a decrease in HP.

Interested in seeing your results. I had my car weighed, and with me in it and a half tank of gas it was 3155 lbs. My numbers are nowhere near 190 HP. I wondering how much altitude has to do with it (4000+ft).

EDIT: Forgot to mention... I tried a few 2nd gear pulls as directed in the user's manual and I tried a few 1/4 mile runs. The HP results were within a couple HP from each other, didn't seem to make that much difference. Curious to see the effect of DSC on the numbers.

With an accelerometer weight has everything to do with the net results. If my car accelerated at the same rate but weighed twice as much then I could expect to see higher HP numbers.

As for my weight I simply added to front and rear weight to arive at my total weight as seen from the door jam.

Like I said before, I will need to get on a scale to know the real weight of the car, along with my four other fat friends. I will try using 3000 pounds next time. With the lower weight I would expect to see a decrease in HP.

The numbers on the door jam are GVWR. That is the MAXIMUM weight of the car when fully loaded.

The actual weight of an RX-8 is around 3000 lbs plus fuel and driver (maybe a bit less, but 3000 is a good starting point)

I just ran a 18 hr, each way, trip from Chicago to Daytona for the 24hr race. After stopping for gas in Georgia, I notice the car had a lot more power and a different exhaust note.
I think the car needs to be run hard for a long distance (500 + miles) every once in a while.

I recall a few others on here with GTech's averaging around 130-bhp readings, 140 max, which everyone knows isn't how much power the 8's are putting to the ground.
And 3600-lbs is super heavy- that's 350Z weight! Try 3100 next time.

Well, I went out again, but I still have not weighed the car yet.
The reason I went out is because I filled up at an overpriced station and I couldn't bring myself to fill up with 91, so I filled up with 89.

Lower octane should produce more power, so I wanted to see if it did.

I go to the same street everytime, and to make an objective test I entered in the same 3600 lbs as before and hit go.

This time the variables were; air temp 52F, 3/4 tank, and 840 miles on Odometer.
Pass 1 - 211 HP - Down the straight shifting just past the buzz - lots of wheel spin
Pass 2 - 201 HP - Return Pass same shifting - no wheel spin
Average: 206 HP

Then I did two more runs at 3000 on the dot this time starting at the opposit end of my track.
Pass 1 - 165 HP - Pissed but not surprised...I chose to call it a night
Pass 2 - 145 HP - Next street over same length and incline - couldn't help but go again -- Really sucky, I should have just left.
Average: 155 HP

Results: Not sure, but the numbers are a tad higher, but the data is very thin and I'm not sure they hold much value.

On a side note, spending a bunch of money on intake, exhaust, headers, ecm, and led mirrors doesn't seem like the brightest thing to do when a tank of lower octane nets better results at a substantually better price.

I'm sure there are people that are making a significant amount of HP over stock with N/A bolt ons, but does it feel faster? Coming from turbo RX-7 owner, 255 turbo HP feels very fast, where as 238 feels painfully slow. Does a 250hp N/A feel as fast as a turbo 250hp?

I think we are now rated at 232hp. Most 8 owners who have dynod stock will pull 170whp-185whp. With N/A mods, you are lucky to get over 200whp. Sadly, the mazda6s is rated at 220hp from mazda and with just an intake those cars can dyno 200whp. Personally the power wasn't the selling point for me to trade my 6s in for an 8. It was everything else.

Use 3100lbs if it's a GT 3000 for a basic.

Then add your weight and fuel weight. your results will be normal, about 175 HP

I had mine weighed on a state scale, with me and a full tank, 3250lbs. I weigh 175lbs.

I had mine weighed on a state scale, with me and a full tank, 3250lbs. I weigh 175lbs.

Perfect, you and I are the same weight. I'm guessing this is close enough to use as a base for future measurements.

Full tank of fuel is 84 lbs, so I'm guessing that anywhere between 3166 and 3250 should be easy to estimate based on fuel level.

I will fill up tomorrow and go give her a run at 3250.


Another side note: I noticed that my numbers were better when I launched the car hard with little wheel spin. Not sure why it matters, but I thought I would leave that tidbit out in the open for others anyway.

Yeah, a high-rpm launch with some wheelspin will give the best times for the 8.

You don't need a hard launch to use the dyno feature on your Gtech. You want an accurate weight, straight and level road and then short shift into second and floor it to get the full power band measurements. Also I'm not sure why you think lower octane will give you more power but give it a try with your Gtech with different octanes. I'm sure people would be interested to see the results...

You don't need a hard launch to use the dyno feature on your Gtech. You want an accurate weight, straight and level road and then short shift into second and floor it to get the full power band measurements. Also I'm not sure why you think lower octane will give you more power but give it a try with your Gtech with different octanes. I'm sure people would be interested to see the results...

As for the octane, all things equal you will extract more combustion from lower octane fuel because the fuel is designed to ignite at lower a temperature (to a point).

Of course with a compensating fuel delivery system like on the RX-8, it may not hold water, but with older vehicles you will extract more power with the lowest/safest octane you can run.

Many people believe in higher octane equals more power, but in reality increasing the ignition temperature point of fuel (higher octane) WITHOUT additional power adders (Turbos, Hi compression, S/C, advanced timing) will remove performance rather than raise it.

The only reason to increase octane is to reduce the likelihood of pre-ignition when aggressive designs are used such as power adders, tuning, and high compression applications.

My hope with the lower octane was to fill up while it still had the premium compensation data and then go for a run and see if it would make more power. In reality I don’t think it made any measurable difference since the variance between each run were so great.

Back on track though, I went for another run with a weight of 3200 lbs at 51F, ¾ Tank 89 Fuel.

1st Pass – 170 HP - Set perfectly at 0 tilt
2nd Pass – 155 HP - set at -1 tilt - Could not get it to level out after 3 minutes
Average – 162 HP

I will try your suggestions the next time out.

there's a mistaken belief on this forum that lower octane doesn't make much difference on an RX-8, very mistaken ...

there's a mistaken belief on this forum that lower octane doesn't make much difference on an RX-8, very mistaken ...

Do you mean it is harmful, or under rated? Couldn't tell by your comments.

Harmful. Any ping is death to a rotary.

Shell gas. It must be in my head, but my car sure feels peppy after I fill up with shell.

When I used my friends G-tech I logged the weight of the veh with driver at 3279 lbs (did not incl my friend @ 210lbs) and shift point was 8500 rpm. I launched between 5000 - 6000 rpms each time with the dsc off. I ran a consistant mid to high 14 with an avg speed between 90 -93 mph in the 1/4. My slowest time was a 14.8. I am only running a Greddy SP2 exhaust and a custom CAI I made several months ago. Overall I was pretty happy especially since I was carrying an extra person that weighs more than I do.

Best times:

60ft - 2.25
1/8 - 9.33 @ 77 mph
1/4 - 14.5 @ 93.6 mph
0-60 was 5.88 sec
AVG WHP was 175.6


60ft - 2.5
1/8 - 9.6 @ 74mph
1/4 - 14.6 @ 92.3 mph
0-60 was in the low 6's

185 RWHP is right in line with a 20% driveline loss, (as normally found on RWD cars).

Shell gas. It must be in my head, but my car sure feels peppy after I fill up with shell.

It could be but my car feels quicker after I fill up with any gas. :dunno:

It could be but my car feels quicker after I fill up with any gas. :dunno:

+1

This is the only car iv'e ever ran out of gas in more than once & I can definately confirm the validity of the above claim

So the factory fwhp is 230?
For US & California Spec models claimed factory HP is 232 in 2006+ SAE standards and 238 in pre'06 SAE standards on unleaded 91 octane (RON).

In europe the bhp is 228 & I would bet my left testicle that it is in the us(maybe not :o: )

In europe the bhp is 228 & I would bet my left testicle that it is in the us, maybe less :o:
You seem to have more issues with the renenis than a uk spec, is it fuel grade or software?

In europe the bhp is 228 & I would bet my left testicle that it is in the us(maybe not :o: )
My UK 05 RX-8 sales brochure says 189.08 hp (141KW) and 227.97 hp (170KW)... remember they have two different reni's there as well.

I recently ran a 15.03 @ 97 MPH with my G-tech. This was my second pass out of two, with the first being a 15.60 @ 91 MPH. Both runs encountered a lot of wheel spin, and looking at the MPH I think a mid 14 is a done deal with a little practice.

185 RWHP is right in line with a 20% driveline loss, (as normally found on RWD cars).

Somewhere on the forum, there is a quote from Speedsource where they indicate their ST class RX-8s were only experiencing losses around 12-13%.

That's why I eschew percentages as driveline losses. There are no "standards".

Frankly, I really don't care too much about losses or how much I started with power number wise. I just care about what was my beginning trap speed, and how much has it improved. Right now I'm NA and could care less. But right before I go FI I will get a baseline trap to measure my improvements, or lack.

I guess the day I can strap a tire on the flywheel and drive with that is the day that I car about fwhp. Less loss fw to wheel or more power at the fw, it still leads to a happier butt dyno.

Although I think the factories claim is a little optimistic, its highly car dependant. These cars seem to dyno bizzarely inconsistently from one to another. They also, as mentioned many times before, seem to vary widely in terms of fuel economy.

Of the two pulls done by stock rx8s at my local DynoDynamics dyno, the HP ranged pretty wildly. The other owners RX8 pulled in the mid 160s, and mine in the 180s (the dyno dynamics is about 7% lower than a mustang dyno and about 15% lower than a dynojet). Both had nice looking curves with the usual dips and no signs of misfire etc.

As an interesting side note, I compared my recent pulls to those of stock wrx pulls performed around the same time. Surprisingly the RX8's peak power was higher than pretty much all of the stock wrx's. Granted the power band was narrower and the torque was much lower. The WRX I believe is rated at around 225 fwhp. So the Mazda claim while high, isn't super outrageous when compared to other industry claims. I think there is just a general HP correction inflation that plauges alot of these cars. People get too fixated on numbers.

What were your launch rpms and clutch technique?

I didn't really pay much attention to the RPMs, but if I had to guess I would say around 6K with a feathered out clucth to WOT.

Traction was a real issue, but on a street I didn't really expect much.

I used to drag race my RX-7 and it took a while to get the feel of the clutch slipping yet pulling. Without turbos, the RX-8 feels very different.

I'm going to try a lower release RPM with more feathering to WOT and see if that gains a better ET.

It's such a fine line between wheel spin, bogging and acceleration that I'm sure it will take several passes to get a clean low ET, but I have no doubt it's in the car.

I am curious to see if this technique works as well for you as it does for me; while staged, hold the rpm's at 5K. While quickly releasing the clutch pedal, but not sidestepping it, floor the gas pedal. The objective is to get clutch lockup around 7-7,500 but not totally hammer the driveline. I have used this method for years, even with nitrous, and I haven't broken anything. Not even my trans. What it allows is full-throttle 7K launches that don't burn the clutch disc. Let me know how it goes.

thats the one i use, riding dirt bikes for years taught it to me...

beers :beer:

Have you tried other methods and does this one work the best for you?

yep,

if you are talkin to me.. and i have photos of the clutch to prove it..

best 60 ft for me came with 24lbs of air in rear.. feathered launch at ~5k rpm.. tc and dsc off... air temp 81deg. btw, i dont do this much any more..

beers :beer:

I prefer to let the clutch last a little longer and roast the tires, instead. That's why I don't "feather" it.

I think its sort of a damned if you do damned if you don't situation. The tire roasting launch is hard on other driveline components, just not the clutch. As noted by other members of this board, I'm exceedingly paranoid about the strain put on a car by launching it. Probably to the point of being a little nuts. I guess its all the research I did in deciding not to buy a CTS-V or a GTO as they eat diffs when they are launched.

old and uncoordinated.. are you mocking me????? i thing you have all the good karma points i lost somewhere when it comes to the car.... not that i have had problems.

just from dirt riding you learn to feather the clutch to keep the traction where you want it... and it seems to work with the car as well.... right now everything i do is about the roll on... no stress.

just got back from helping someone with bad 5th and 6 syncros... glad i have a spare tranny...:) :)

beers :beer:

How can anybody be concerned about their driveline after all the hammering I have done to my car over the past three years? I have literally TRIED to blow up my diff by having wheelhop during nitrous use and it still won't die. My tranny-I have missed I don't know how many 3rd gear shifts and it still feels smooth. Of course, I discovered that the problem wasn't me getting old and uncoordinated. It was the pedal bracket. Since then my shifting is smooth as glass and I never miss a gear.

Drag radials/slicks are a different story, though.

Does the 8 get a lot of wheel hop with hard clutch dumps. Never really launched mine, always get on it from a roll. I assumed since the synchros were a little weenie, that the rest of the driveline followed suit. Totally unfounded conclusion apparently.

I'll take your word for it on the hard launches as few people on this board are as credible as a source. That said, I think I'll remain a wuss and not launch my car. Although its still under warranty... See, now I've been corrupted!

Does the 8 get a lot of wheel hop with hard clutch dumps. Never really launched mine, always get on it from a roll. I assumed since the synchros were a little weenie, that the rest of the driveline followed suit. Totally unfounded conclusion apparently.

I'll take your word for it on the hard launches as few people on this board are as credible as a source. That said, I think I'll remain a wuss and not launch my car. Although its still under warranty... See, now I've been corrupted!

yes. tire inflation is important..

beers :beer:

yes. tire inflation is important..

beers :beer:

This is why I don't drag race, I wouldn't even know what way to go with the tire pressure for a good launch! I'm totally un-edjumacated!

wheel hop is a big issue with this car..


beers :beer:

For me, even with nitrous use, the RB swaybars eliminated the wheelhop under 99% of the conditions I have encountered. It was the once or twice that I have run into it that I decided were my chances to try and blow the rear diff. Still works great. I have never liked the factory tires so I use Nitto-555 Extremes. Pretty decent tire.


one of the last things i have not done.. go figure..

beers :beer:

I tried your 5k drop to WOT and all I got was major spin. This was on the street, so perhaps I need to lower it.