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Originally Posted by Joey911
Quote:
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Originally Posted by black_vicking
I don't know if this has already been answered, if it was I apologize in advance, but I'm looking to do my 2012 335i quad exhaust by installing a e92 M3 muffler, does anybody knows if it fits in the 335i? I know I will have to change the difuser on the car.
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 to whoever asks this again with no fear of people telling you to search first, or shitting on you
I too wonder the same, more interested in M4 exhaust to E92 335i, since they're both turbo inline 6 engine.
I'm sure people will tell you this: "NA engine needs back pressure whereas FI engine need 0 back pressure."
I recently read this article: http://www.gomog.com/allmorgan/exhaustbackpressure.html
It's about exhaust gas velocity vs piping diameter and such, might explain why people looses low end torque when going for a fatter pipe, but more HP at the top end.
It also mention that BMW uses this technique to control the exhaust gas velocity.... Our muffler flap! Which makes me wonder, does the flap closes at lower RPM makes a little more torque because of the exhaust velocity is higher with the flap closes (so called more back pressure)?
Please read it and discuss 
I want my car to sound like M4 though lol
Joey |
Makes sense. I disabled my flapper to get more sound all the time. But if it is by design.... hmmm making me second guess my plans for a HFDP and PE mod exhaust.
Addendum:
I found this on bimmerfest.
Here is the official BMW explination:-
Thank you for your email to BMW Customer Information.
We can advise that the exhaust flaps adjust at differing engine speeds in order to make the most effective use of the exhaust silencer. When the vehicle is running at idle or at low RPM, the flap ensures that the exhaust gases use as much of the silencer's volume as possible, keeping exhaust noise down, e.g. when you're in slow traffic or driving in high gear.
Whereas when the vehicle is running at high RPM, the exhaust flow characteristics are adjusted by the flap to give the exhaust gases a more direct route through the silencer, thus using less of its volume. This also has the effect of allowing the engine to rev more freely as there is less restriction on the exhaust flow.
The primary reason for the flap is to make the most effective use of the exhaust silencer volume at differing engine speeds.
We trust this information is of some assistance to you but if we can help you further at any time, please do contact a member of the BMW Customer Information Team.
Yours sincerely
BMW Group UK
Elfriede McNeal
Product Information Advisor