Power mods for the I-5

[ChevyHighPerformance]

Originally Posted by f5fstop

Hope that is not from the southwest and some "GM engineer." Just a note, I can take any dyno graph and change it the way I like it. Not saying this is what happened, but, if GM could raise the HP (safely) with a tune, and a new cat back system and airbox, they would have already done it. I say safely, but I also mean legally.

This is not my dyno graph. This is from another post from another H3 forum. I was just providing it as an example. You can look in Colordao/Canyon forums for other dynos. Here is a dyno on a dynojet by K&N for an H3. In stock form the drivetrain efficiency (on this inertial dyno) was 75% or 25% loss (0.25 * 220 HP = 55 hp loss)

http://www.kandn.com/dynocharts/77-3044.pdf

I'm not surprised by the 65% drivetrain efficiency with dyno that properly loads down a 4WD vehicle like a Mustang dyno. Here is another dyno from K&N for a colorado same 3.5 L engine but 2WD and the stock HP is 180 hp (compare to 165 hp for the H3).

http://www.kandn.com/dynocharts/63-1095.pdf

The difference peak HP is due to the drivetrain efficiency ~82% for the 2WD colorado and 75% for the H3 on an inertial dyno.

GM has to tune for the masses. Because of production tolerances, different environments, different local fuel, etc. GM can't tune to the performance edge. GM uses a consevative ~11.9:1 A/F at WOT when most tuners bump that to 12.8:1 or so for more power.

GM has noise goals to meet. In the past, GM would ship a Z28 to SLP to have and intake, exhaust, etc. put on and SLP would not have to meet the noise requirements that GM had to meet. A new H3 airbox that eliminates the resonator will have more noise as well as a free flowing exhaust. For the new Z06, GM designed a cutout, so when you went to WOT (which does not have noise requirements) the cutouts opened for more power and substanially more noise.