E36 328 exhausts valve?

Can anybody give me some information about what appears to be a valve in the right hand tailpipe of my 98 e36 328 coupe. It appears to be closed all the time while the car is stationary and the engine is revved. Also, are there any implications for fitting a Scorpion stainless DTM system?

Thanks in Advance
Dave Penna

What you are seeing is what's called the Butterfly valve. For most of the normal car procedures, the valve remains closed and makes the exhaust gases go through a convaluted route. However, when under a large amount of stress (downshifting, acceleration on the highway, etc) the valve will open, permitting the exhaust gases a straight shot out.

Thanks Jules, that makes sense as all the 328s i see in the town always have that closed. I thought it was just a fake tailpipe until i bought this car and noticed that the valve moves
Dave.

The shut valve under low rpms is used to create more backpressure. The problem with big diameter aftermarket exhausts are that you loose the backpressure with is important in low rpm power. But you make it up in high rpm gain.