[Blue2]

I've read anecdotal stories of people feeling less "low end torque" after doing a muffler delete on the M235i/335i. Has anyone here experienced that? Are there any dyno sheets to support/debunk the claim?

[mike@x-ph.com]

There will be no noticeable loss of power

[Fabspeed Motorsport]

Mike is correct. After installing my Muffler Bypass (with Sport Cat Downpipe) there was no noticeable loss in power. The Muffler Bypass is mainly a sound changer. It really opened up the exhaust note coupled with the Sport Cat.

[XutvJet]

Loss of ultimate power? Nope. Loss of part-throttle response in the lower rpms? Very likely. Reduced throttle response can give the perception of reduced power. My guess is this is what people are referring to.

Why does this happen? It's due to volumetric efficiency, exhaust pulses, and cooling of the exhaust as it travels through the exhaust pipe. By running a high flow exhaust and driving at lower rpms (especially off boost), the exhaust gases can cool quickly thus reducing their flow. What you feel is reduced throttle response and bogginess. In naturally aspirated cars the effect can be very apparent. Once you go full throttle, the exhaust gases are hot and will flow quickly plus turbos don't like restriction downstream of the turbo. OEM exhaust design on performance cars try to accomplish the best drivability for all situations.

This is just another case of "race car parts on street cars sometimes isn't ideal".

[Blue2]

Thanks!