E36 back box valve?

[zoidberg]

I've just been reading on another forum () about a valve in the back box of the E36 which opens and closes via a vacuum pump connected to the inlet manifold. You can apparently block off the pipe and the end of the valve so both pipes stay open to give a nice subtle increase in engine noise...

Anyone know any more about this?

[flagellant]

there's an electrical connector in the boot (by the passenger side rear light cluster) under the carpet and plastic that you can simply unplug.

[zoidberg]

Sounds good - can you tell me a bit more - colour/what it looks like etc? What's it actually do when you unplug it?

[flagellant]

If you leave your car with the engine running and look at the two exhaust pipes, you'll see that one is blocked off by a butterfly value - This could either be to keep noise down at low engine speeds and/or provide some back pressure in the exhaust system. When you accelerate (or at higher speeds?) it will open.

When you disconnect the switch this butterfly valve is left in the open position so both exhausts are always unobstructed = more noise and you may lose a little low end performance.

The connectors on mine are about the size of a small matchbox when clicked together, no tools were required to disconnect/reconnect.

[zoidberg]

Thanks for the info - I have unclipped it and there's definitely more of a burble now

[Aeroresh]

Does this apply to all E36's or just certain engines?

Ive got an M3 Evo track car that would benefit from this subltle mod if poss!

[Chris71]

Is this purely done for noise? Surely you want it quite when pottering when town and then have a valve that opens when you give it some beans?