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      09-13-2010, 04:13 PM   #64
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Drives: blue
Join Date: Jan 2007
Location: f y'all, I'm from Texas (RGV)

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Originally Posted by Doug007 View Post
2x 2.5" diameter pipes has an area that is about equivalent to a single 3.5" pipe.

I see your point about clearance. You could always try to oval the pipe a bit to maintain the same area with a smaller vertical dimension. As long as it's not too extreme, it won't have a huge effect on backpressure. It's primarily a question of flow area.

The biggest gain will be just replacing/removing that huge catalytic converter. The pipe sizes/arrangements past that will be insignificant compared to a high flow cat or none at all.
What cat? I know on the 335i n55 there are no cats or res on the pipes...
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