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Discussion Starter #1
Hi!

What is the stock single exhaust size on a M50 320i?

Have installed a single 60mm pipe with two straight through glasspack mufflers.....no cat convertor. Very quiet at idle and cruise.

What power gains should I expect?

TIA
 

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hi i wouldnt of thought very much,maybe 5-10bhp but dont quote me on that as could be a bit less or a bit more,trouble is with de-catting you wont get an mot without it and car could run rich or lean,unless you are going to put it back on for mot which im sure you will lol!:)
 

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hi i wouldnt of thought very much,maybe 5-10bhp but dont quote me on that as could be a bit less or a bit more,trouble is with de-catting you wont get an mot without it and car could run rich or lean,unless you are going to put it back on for mot which im sure you will lol!:)
Doubt they have MOT in SA :hihi

Stock size is 52mm IIRC. Hard to say how much you will gain, not uncommon for the car to actually loose power sometimes..
 

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Discussion Starter #4
Just wondering, the 2.5L gets 48mm dual exhausts and the 2.0L gets a 52mm single? If a de-cat and free flow exhaust supposedly make power on a 325i, shouldnt the same apply to the 320i with a more restrictive system?

mikey28,

No MOT:thumbsup

Wont the DME adjust the fueling according to the new airflow through the engine?

ShamM3,

You are right about losing power sometimes with a freer exhaust, but thats only if the engine runs lean. Usually, with the right AFR, the power-band is shifted higher.
 

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iv spoke to many people about this and the answer is always the same... its not worth it. the maximum gain you should see is about 3hp which you would never notice, and by doing this you make your car illegal.
 
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