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Old 06-14-2012, 09:09 AM   #258
diablorojo
Registered User
 
Join Date: Oct 2008
Location: Atlanta, GA ..now Houston, TX
Posts: 318
My Ride: Supercharged 330i
Question

Getting a custom exhaust fabricated today. Didn't plan on it, but when I removed the rear section of the muffler and measured the diameter of the dual pipes I learned that it was only 2 inches. I was surprised because it was a full Borla exhaust that I purchased years back. That may even explain some of the choking I was experiencing down low.

So now for the new exhaust. Research is indicating that the max HP on 3 in single is roughly 400 HP. Dual 2.5 is roughly 500 HP. The problem, it has to single into a three inch to feed the turbo. If I dual 2.5 from the header to a 3 in single, say midway, aren't I still limiting the system as if it were a single 3 in exhaust?

If the answer is yes, then I might as well do a single 3 in all the way back.

As of now I'm thinking the best set up would be dual 2.25, yes 2.25, with dual resonators (thinking the resonators will slow the flow as much as a dual 2.5 inch setup will) into the 3 inch. Quiet is king for me. I know this will choke off on high HP for regular turbos but not sure how a rear mount would respond. Also, I'm trying to maintain balance because the less exhaust flow the more lag the turbo would see.

I'll be dropping the current exhaust off this evening so I have a little time to try and figure this out...
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