Question on the X3 tailpipe..
 

As I was installing my new hitch, I noticed that the left tailpipe has a 'Butterfly' (valve) that opens and closes. It was closed while idling, I drove it for about an hour and noticed it was still closed? What's it for and when does it open?

I checked my Z4 and it doesn't have that valve.

It opens at high power for better performance.

Cheers

It regulates exhaust back-pressure for better engine efficiency throughout the rpm range. A certain amount of back-pressure is desireable to help keep the incoming fuel charge from being sucked out the exhaust during the overlap period between the intake and exhaust valves. As rpm's increase it opens to allow the larger amount of exhaust gasses to pass more freely.

I don't think mine has this.

Maybe it also helps to avoid having water entering the exaust pipe when the car is under water (I mean, up to 50 cms) :) Dunno, I'll search for the valve later on the car.

Sport Package does not have it just in case your looking for it.

Does the Sports Package use a different exhaust?

Not sure about the whole exhaust but the finale muffler / tailpipes seem to be different. The diameter of the tips are different then the non-sport as well as the sport has stainless tips, non sports do not and the sport does not have the flapper valve

Here's a picture of the valve.
http://i114.photobucket.com/albums/n...3/Tailpipe.jpg

we did this a couple of years ago

http://www.x3world.com/x3-e83-forum/...?highlight=tee