Hi guys. I see a lot of post of G's with cat back exhaust. I want to gain as much horsepower as I can. I live in a state that doesn't have emissions test. What would you suggest. I have a 2010 S coupe.

 

Welcome to the forum. The most horsepower setup would be test pipes and a custom 3" exhaust. If you've searched around the forum to see the different types of exhaust, then you know that the engine in your G doesn't respond as well to bolt ons as other cars would. The biggest horsepower mod you can do is forced induction. One exhaust is very much like any other, the differences would be build quality and the sound it generates.

GTHaus, Fast Intentions, Motordyne Shockwave, Borla, HKS, Apexi, Greddy, and Stillen are all good brands.

You should be looking for an exhaust with mandrel bends, few sharp angles, and large diameter.

 

Ditto to what Nguyen said. Most of the exhaust are comparable. The differences are really in the appearance, brand, and sound. There may be slight add-ons such as HFC or test pipes that may improve/decrease performance depending on your set-up. Some popular brands for the coupe are: Amuse, M7 Japan, HKS, Fast Intentions, Greddy, Ark, Tanabe, MXP, Invidia, Stillen, Meisterschaft, Fujitsubo among others.

 

Thanks for the info. If I'm going to do the exhaust should I just save up and do the headers at the same time?

 

Your car already has headers, the only upgrades are long tube headers. Did you mean cats? Or an intake manifold? Or intakes?

 

 

 

Recommend 2.25-2.5'' for an NA build.

 

I would still agree with the 2.25 making better power vs the 2.5 making extra noise.
not sure why you would need a total of a 5 inch exhaust system considering it it a dual setup. The gases began to cool down the farther from the headers so smaller pipes would be better for a scavenging effect. Hence the single exit is better for a 6 cylinder car vs the 5 inch catback. I believe the hellcat reduces its factory exhaust system as well and that's a quick production car.