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

 

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.

 

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.

 

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...

 

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 ...

 

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).

 

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

 

+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