Boost and Exhaust

NFAM3 · 05-03-2011, 09:20 PM

Hey everyone. I'm new to the M3 family but I've been in the performance scene for a very long time. I have a question. Here goes...

I have my M3 and I decide to go buy a AA exhaust w X-pipes. These exhaust are made to give you more power and torque correct. The diameter of the piping is a certain size to give you just enough back-pressure. Car runs great. I'm very happy.

Now I decide to supercharged my car. Wouldn't the piping need to be bigger now since I would need less back-pressure to make more power?

I'm asking bc in my old car, you wanted back pressure when you were all motor but once you went turbo, you wanted bigger piping. Does the same not apply to these cars? Won't they make more power w bigger piping once force induction is introduced?

ScorpionT · 05-03-2011, 10:04 PM

Backpressure and torque gains are a myth. Dont worry, its a pretty common mis-understanding. Because you have a positive pressure source on the intake side, you essentially want the most free flowing exhaust possible. The stock headers are sufficient (I would guess until a minimum of 600whp), but I would use high flow cats or test pipes and pair it with a good cat back.

05-03-2011, 09:20 PM	#1
NFAM3 Lieutenant 157 Rep 522 Posts Drives: 2011 M3 Join Date: Apr 2011 Location: Miami, FL iTrader: (0)	Boost and Exhaust Hey everyone. I'm new to the M3 family but I've been in the performance scene for a very long time. I have a question. Here goes... I have my M3 and I decide to go buy a AA exhaust w X-pipes. These exhaust are made to give you more power and torque correct. The diameter of the piping is a certain size to give you just enough back-pressure. Car runs great. I'm very happy. Now I decide to supercharged my car. Wouldn't the piping need to be bigger now since I would need less back-pressure to make more power? I'm asking bc in my old car, you wanted back pressure when you were all motor but once you went turbo, you wanted bigger piping. Does the same not apply to these cars? Won't they make more power w bigger piping once force induction is introduced?
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05-03-2011, 10:04 PM	#2
ScorpionT Private First Class 6 Rep 101 Posts Drives: 335i, SL65 Join Date: Apr 2011 Location: Arctic Circle iTrader: (0)	Backpressure and torque gains are a myth. Dont worry, its a pretty common mis-understanding. Because you have a positive pressure source on the intake side, you essentially want the most free flowing exhaust possible. The stock headers are sufficient (I would guess until a minimum of 600whp), but I would use high flow cats or test pipes and pair it with a good cat back.
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