316i sports exhaust lost power

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  1. 316i sports exhaust lost power 
    #1
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    Yesterday I fitted a sports exhaust to my e36 316i compact, it runs from the cat back. I wasn't expecting any performance gain really, just needed a new exhaust, but the car actually feels slower and less willing/eager.

    I can't find any leaks, does anyone know why this has happened and how I can restore the lost performance?

    Do I need a K&N type cone filter or should I chip/remap it now?

    The old standard exhaust was shot, so can't really put that back. Im not looking for more power, just to restore the lost power, the car used to be nippy and free reving. I've looked all over the net and some people think you need the back pressure of the stock exhaust for full power and some say not.

    Any advice would be great, as upto now im really disappointed my new exhaust has made the car slower to drive
     
     

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    #2
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    What pipe diameter was fitted? It's possible you've increased the back pressure too much which would explain the loss of power.
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    got a magnex cat back on mine and mine revved better after fitting and my original exhaust was in good condition so I'd guess it is the diameter
     
     

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    also take your airbox out and the inlet has a cone shape in the bottom take this out and you get a bit more induction roar and makes it rev better opens inlet from 15mm to 38mm held in by a screw underneath takes under 10 mins
     
     

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    Apple_cart (20-08-2011)

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    Thanks for the reply's.

    The new exhaust is a sportex cat back system, with a 3" diameter pipe. The stock exhaust was about 2" diameter, so in theory there should be less back pressure?

    Will try taking out the cone from the induction pipe, that may help. But still doesn't explain the loss of power with the new exhaust. Any other ideas? I can't feel a leak anywhere.
     
     

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    imho a 3" diameter is too large.think that is standard for the m3.so that could be the problem?
     
     

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    Apple_cart (20-08-2011)

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    the 3 inch diameter is to big lost all backpressure which is needed for scavengingin the cylinders 3in is wots fitted to my bros mit evo 5 . Mine is stock diameter to backbox and tailpipe is 3.5 inch
     
     

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    Apple_cart (20-08-2011)

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    Found the problem! I did the test where you put your hand over the tailpipe which should stall the car if there are no leaks and it didn't stall. There are no leaks at the joint with the cat, but the box is faulty, the seam on the box is leaking badly. So im going to return it to the shop. I think after what you guys said about 3" being to big, I will ask for a refund rather than replacement and spend a bit more to get a Scorpion system instead as they are 2" to the box.

    Thanks for all the quick reply's and good advice
     
     

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    glad you got to the root of the problem and good plan with sticking to stock diameter tubing 3in would be fine if it was supercharged but not for n/a
     
     

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    #10
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    Quote Originally Posted by dazza316i View Post
    glad you got to the root of the problem and good plan with sticking to stock diameter tubing 3in would be fine if it was supercharged but not for n/a
    Cheers mate. Can I ask where you got your Magnex system from and are you pleased with it? I don't want a loud system, just a nice burble at idle, would you recommend it?

    Does an extra inch diameter of the pipe from the cat to rear box really make a difference then, I would have guessed that any scavenging would happen before the cat, which is in the middle of the car?

    P.S. Good forum this!
     
     

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