What size exhaust?
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From: North Jersey
the whole point of changing your exhaust is for it to be less restrictive... by starting with a 3" downpipe, then going to a 2.5" catback, youre creating the very restriction you're trying to avoid by swapping the pipes... i would keep it all the same size
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Yes you lose torque, if you go from a 2.5" to a 3". Why else would DWK5150 be looking to go back to a 2.5" exhaust? New Era Performance, who's a vendor on here, dyno'd a modded Cobalt SS/SC. They started with a 2.5" magnaflow cat-back and went to a 3" cat-back. Again, this is a MODDED, pullied, cobalt, that already had a header and downpipe. They showed a 0 horsepower gain, and a 2+ft lb of torque LOSS ACROSS THE BOARD.
As for your comment about it being pointless to open up the flow before the cat, that just shows your ignorance on modding FI cars. Headers work great at getting rid of heat, decreasing boost, and killing KR. As for the JBP website comment, sure, if you go from stock to a 3" exhaust at the same time as you do the header, you're going to show gain. DUH. But if you do a test on a car that already has a header/downpipe, and then switch from 2.5" to a 3", then you'll see a torque loss. I've spoken to someone that had corsa, and then went to vibrant, and noticed a definete torque loss in the bottom rpms.
As for your comment about it being pointless to open up the flow before the cat, that just shows your ignorance on modding FI cars. Headers work great at getting rid of heat, decreasing boost, and killing KR. As for the JBP website comment, sure, if you go from stock to a 3" exhaust at the same time as you do the header, you're going to show gain. DUH. But if you do a test on a car that already has a header/downpipe, and then switch from 2.5" to a 3", then you'll see a torque loss. I've spoken to someone that had corsa, and then went to vibrant, and noticed a definete torque loss in the bottom rpms.
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From: Midwest
My reasoning for going with the 3" downpipe and 2.5" cat back is because I don't have to mess with the downpipe later on if I want to swap things around. But honestly, I have a 3" exhaust on the Talon, and it's just too loud.
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From: North Jersey
Yes, he has complained about sound. However, if you think about it, if sound was the ONLY reason, he'd just find a bigger resonator and a quieter muffler. I've talked with him via PM's, and he lost alot more low end torque than he wanted.
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From: J-Town, Wisconsin
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Iam currently in the process of re-doing my whole exhaust, 3inch is just to much for me, its loud, and the loss of torque down low is just a killer for me, iam doing a 2.5" header back, with cat this time, i cant stand the sound of this car catless, sounds like a honda buzing down the street.
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