[cssnms]

Does anyone know the stock exhaust pipe diameter from the cat back to the muffler?

The pipeing is more of an oval shape from the DPF to the cat, then it becomes a standard round pipe as it exits the cat. Trying to figure out if it's closer to 57mm or closer to 63mm. My guess is it's closer to 57mm at the widest point and crimped down at the bends to a smaller 53mm.

[spirocheter]

Sorry I can't help with dimensions, though just interested in why you are asking? Considering a replacement??

[cssnms]

Originally Posted by spirocheter

Sorry I can't help with dimensions, though just interested in why you are asking? Considering a replacement??

Yes I have a fabricator that will be making up a cat back mandrel bent stainless steel exhaust. Looking for weight savings, improved sound and hopefully a slight increase in hp. To improve flow I was thinking of increasing the diameter of the piping a little vs stock. Thinking of going with 70mm but also considering 77mm to stainless resonators rather a typical performance muffler.

After reading a number of threads by some of the pioneers in the UK it sounds like there is no sound benefit when installing a performance muffler designed for the petrol e90 and to get any sound one needs to go straight pipe or resonators.

Also sounds like hp gains are negligable, but would like to hear from the guys at Evolve after testing the Supersprint system or Scorpian. Both of these threads have totally died. Guess if the results were worth posting about they would have shared.