LS4 Performance - Dyno Results (05 GXP)

05 GXP, Ivory White, NAV, CAI industries Intake, Magnaflow Cat Back, MGS tune, Really Didn't gain all that much, 347 horse at Engine, 260 wheel horse, 330
foot lbs torque. Thought there would be a little more than that.

No way a 323 lb-ft rated engine puts 330 to the ground with those few mods. Also your dyno operator is using a 25% drive-train loss factor if they are telling you 260 wheel horses translates to 347 at the crank, wildly inflated number there. You need to post your graph, likely you are getting a false torque spike from the t/c. The 260 does sound reasonable based on the mods and what others have been getting stock though, but a more reasonable number for the crank output would be in the 320 horse range. Very respectable numbers, make no mistake, nothing to be disapointed in from the relatively small engine.

edit below, wrote wrong drive-train loss factor, should be 25%, not 33% (fixed). I used the more stock 19% number to calculate the 320 estimate.

I agree something isn't right, I think your dyno operator might be an idiot

yeah. you're seeing the torque that high due to the converter.. should be putting out about 270'ish.. figure tune and the other mods maybe another 10-15 to the tire so around 285 on the high..

See they had a car show in the town I am from and they had a portable Dyno there So I figured that I would put it on just to see what it has. 265.7 wheel horse, 336.9 foot lbs torque, 3rd gear at 163mph wheel speed and 6200 RPM is what the dyno said. A guy that was there was calculating what it would be at engine with a formula he had on his palm pilot and he was telling people what it should be close to so I was going off of that. The dyno's printer was down so the dyno operators said that they would Email the results to me and as soon as they do I will post it. Does anybody know how to figure the HP at the engine from what I have posted. Thanx

Stock ones are putting out about 245 horsepower. With a 303 rating, that gives ~19% loss at the wheels. If the 260 to the ground is right, that same 19% would give you 321 horses. If you go with the 58 horsepower difference between the 303 and the 245 and add that to the 260, you get 318 horsepower. The real number is probably somewhere in between (and within the error rate of a well-run dyno), so see my first post (#2 above); in the 320 horsepower range. Assuming all the measured numbers are correct of course. And his Palm Pilot? All he was doing was (and my number in the #2 post of 33% was wrong, went temporarily insane or something when I typed it, figured the 320 with the correct number originally, just typed it wrong in the post, it really is a 25% drivetrain loss factor, edited now in the above post) using a formula that everyone learned in basic algebra and calculating for X, where X = calculated horsepower. (X-0.25X) = 260 or X = 346.7 The dyno operator wanted people to think their car had substantially more power than it does. What better way to drum up business than to have people all excited about how strong their car is? Still very very nice for 325 cubic inches of 2 valve motor.

Thanks a lot for the input. I thought there was something wrong with the results. I really don't know that much about dyno results. I just wanted to know what it really has. Because they say all this horse power gains but I really didn't feel what the claimed. Like exhaust the claimed 20 hp gain. CAI 3 to 7 hp, Tune 15 to 20%, Jeeez that would be like 30 to 40 hp gain. Now I know what it is. They must not do to much testing when they post results. How much more power do you think we can pull out of these LS4's. Thanks a lot

You have to be real careful when looking at results posted. Perhaps they are at a different air inlet temp, outside temp? Was the car allowed to fully heat up before each run? Were both runs in the same gear? There are a lot of things that needed to be considered to deem two runs equivalent

Here is the Dyno Sheet that was sent to me

Ok, what I see is the converter giving a false reading until the graph starts to jump around (when the engine starts seeing more load), it is right under the peak torque RPM rating of the LS4, so it is probably a pretty decently accurate number, call it 285 lb-ft of torque as a peak. Not sure what a stock one puts out, but I would think you are looking at ~335 lb-ft at the crank and the 260 horses seems to be about right.

I’m a little confused looking at this sheet. I’ve always read that the HP and TQ curves are supposed to cross at 5250. Also I thought the rev limit on these where about 6100 or so and this chart has it making power to 6700.

the scale is not the same, look at each side, one is power the other is torque. If you go to 5252 on the RPM range, you will see that both graphs share the same value relative to their particular side even though the graphic representation does not visually show them crossing at that point.

Interesting, I see what your talking about to match the values. Any idea on the exaggerated power band?

Not stock program, rev limiter is raised. Power drops off around 5800 so probably not really any benefit beyond reving past 6200 or so as the cam/springs seem to limit the peak output to 500 RPM below that. Probably would be faster shifting it just past 6100 and not trying to run it up to 6700

Here is a dyno from a stock vs. tuned 06 MCSS on the same dyno, same day.

Thanks
Mike

If anybody is interested I am selling this GXP or if they know anybody looking for one. I would like to get around 19 for it