2.5 inch exhaust vs 3 inch

mtang98 gt

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Hey guys my current set up is leaving me wondering if its time to up the exhaust from 2.5 inch out the back to 3 inch. I currently have a hand ported pi intake manifold, cnc ported heads with fairly large cams, bbk shorty headers running into a offroad xpipe glasspacks and flowmaster tailpipes. Any help is appreciated thanks!
 

Caboose302

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I don't really think a 3" in "needed" until your boosted or pushing a lot of hp. My old Camaro had 360 hp and had that goofy 3" single exhaust and breathed just fine. In some cases I would think the loss of back pressure would cost hp.
 
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mtang98 gt

mtang98 gt

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seems that the general consensus is to keep running 2.5 thanks for the help! now to find a nice set of mac longtubes
 

Caboose302

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Other than stock, where would he find 2.25 exhaust? I think if you're talking about a bolt on car then I don't think you get much difference, but once you start talking about ported heads, intakes and cams, the mandrel bent 2.5 is going to help it breath better.
 

96blak54

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Exactly. ..if all you can budget is swapping out the stock cat H-pipe for a 2.5 aftermarket catless ...thats the major improvement. Ditching the cats is were its at!
 

97stanger

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You are definitely not in the range for needing 3" exhaust. I've seen it become a restriction in the 700rwhp range before on a buddy's car, but unless you are running crazy boost I would just stick with 2.5"
 

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