QuestionThanks for answering. I went and checked the diameter of my exhaust, and it is actually about 1 3/4"~2", with the tip around 3 1/4". The GMPP Cat-back upgrade adds 12 hp, but I don't think the diameter will vary much, if anything. Also, GM sells an Extrude-honed Exhaust Manifold, and they say it increases air flow by 7%, but I am feeling skeptical about that amount [everything is current-based knowledge]. So...
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I have a Chevy Cobalt SS Supercharged, 2.0L FWD. I just ordered a new CAI, and I was wondering if it really would be significantly better to get a new header-back exhaust before I get the GM Stage 2 kit for my car. It includes: Shorter belt/pulley system for the s/c, high-flow fuel injectors, and a recalibration of the ECU. Adds 36 hp & 18 ft/lb torque. I guess what I really want to know is: Will the stock exhaust system be too restrictive?
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Do you happen to know the diameter of the exhaust? Generally I would say yes, on a car like yours the exhaust is to restrictive. If the price of a 3” exhaust is a little to much at the moment, put in a high flow catalytic converter until you can afford the exhaust you want. I put a 3" on my SRT-4 and I love it.
AnswerAn upgraded exhaust would give you more benefit than an extrude honed manifold. I would start there and then worry about changing your manifold out. 7% is not unrealistic by any means in regards to increased flow...but it wouldn't make your catalytic converter flow any better.
http://cgi.ebay.com/ebaymotors/MEGAN-Catback-Exhaust-Drift-Spec-06-07-Chevy-Coba
This exhaust system looks to be well built and will out perform (in my opinion) the OE upgrade any day. I have had a few things from Megan Racing and have never had a fitment or quality issue, the price is right too.
