I know there are many threads about the GMPP cat-back. HOWEVER, I don't believe ANYONE has really dynoed their car with the cat-back only. I've searched HIGH and LOW no website (not this nor others) can tell what are the gains.
Then, after hours of searching, I've hit this site: 2007 Chevy Cobalt Exhaust Upgrade - GM High-Tech Performance Magazine
I don't know if everyone read it, but the GMPP performance exhaust was installed on the SS 2.4 the only gains were 1.2HPs??!?!?!? My jaw dropped after looking at their dyno sheet. I understand that maybe perhaps that the 2.4 has a less restrictive exhaust and they have an auto version, but even at that, how much is there to gain from this?!?
This is really disapointing to see, I don't think people's "butt dyno" is very accurate. Sure the exhaust "sounds faster" but I now question it's actualy potential on the 2.2?
If you read on the article, after they drop in the GMPP intake (mine's on the way), they then gained 6.8hp. I assume that's because they already have the exhaust in place, but seriously, almost a grand worth of upgrades for a mere 8 hps? I mean it is a 2.4, but are we going to see better gains than that? It's essentially the same motor, but larger displacement no?