bmw exhaust

[top_driver]

hi, im just curious to know, on the back of my exhaust in one of the tailpipes, the is like a flap that looks like it opens and closes, it looks similar to an air intake thing on aengine, what is it for and what does it do

[ChuckFickens]

http://www.honestjohn...ost/index.htm?t=62001

[TWR]

Stops water enetering the Exhaust T/ Driver.