BMW active exhaust questions

[Mr Whippy]

I've seen on some 3.0 3 series a flap in the exhaust open and close.

Does this work on vaccum actuation (bit like a wastegate, but vacuum?)

Does anyone have a picture on the insides of one of BMW's active exhausts?


Wanting to tinker with the idea of an active exhaust but ideally want a Z4 back box spare, and a 330 one to use for parts. Does anyone know a good place to source both these from?


Many thanks

Dave

[Martyn D]

It does work on vacumn trigger by a micro-switch which opens the flap as the revs increase, was put in place to keep noise down while "city" driving...mostly they get either stuck open or closed