Z3 2.8 new backbox new power?

[id101]

Just had a new custom backbox to replace the old standard one for a bit more sound (too much sound now unfortunately!) But what I think I noticed is a noticible difference when hitting about 4k rpm that wasn't there before. This could be a placebo effect of more sound, but just wondered if the less restriction would make any real difference

 

[JimS]

From my previous efforts at modifying cars you could get 3-5bhp at top end from a less restrictive silencer with no other changes to exhaust. That's similar to changing the paper air filter for something like a KN filter, so that would be my next mod for a bit more noise, which usually tricks your brain into thinking it's a lot faster.
Of course the only real way to know is to have it Dyno tested and preferably the ECU programmed to maximize what is available.

 

[id101]

From my previous efforts at modifying cars you could get 3-5bhp at top end from a less restrictive silencer with no other changes to exhaust. That's similar to changing the paper air filter for something like a KN filter, so that would be my next mod for a bit more noise, which usually tricks your brain into thinking it's a lot faster.
Of course the only real way to know is to have it Dyno tested and preferably the ECU programmed to maximize what is available.

It probably is placebo effect it just seems to rev out a lot more hits the red line more easily