Need help with downpipe

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Dec 25, 2007 | 04:18 PM

71chevellels1

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Need help with downpipe

Im running a 76mm turbo and my exhaust outlet on the turbo is 3.5 inches but i want a run a 4 or 5 inch DP. Its just going to be a 90 degree dump so do i buy a 3.5" 90 bend and a 4 or 5 inch to 3.5 reducer? What are you guys using? Thanks

Dec 25, 2007 | 05:21 PM

pwrtrip75

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From: Janesville, WI

depending on how long your exhaust is, each elbow adds the same flow as like 4' of straight pipe (something like that) So the more elbows you use it is better to step it up. If it just a dump, I'd leave it at 3.5" ........my opinion.

Dec 25, 2007 | 07:25 PM

White.Lightning

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From: Aston, PA

Isn't 3.5" sufficient for a 76mm turbo? I see some 88mm guys running 4" DP's.

Andy

Dec 25, 2007 | 08:17 PM

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From: Buffalo

3" is enough for a 76gts, especially if it's dumped.

been there done that

Dec 26, 2007 | 08:01 AM

Big Geek

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From: Montgomery, AL.

I have seen gains made by swapping out a 3-in. DP to a larger 3.5 and 4-in. DP. This is not to say that you can't run the numbers with a 3-in. as I have seen some do just that, but as I stated I have seen cars pick up power and ET by upping the DP size. It is a good rule of thumb to utilize as large a DP as reasonable, it is one of the few areas where most of the time bigger is better. Hope this helps.

Jim C.