Just to clarify for everyone... DEFAULT (when the car is off) position of the flap is OPEN. When the car is started, air pressure is applied to the actuator through the vacuum hose, which in turn causes the flap to CLOSE. It REOPENS when increased RPMs and/or throttle load are present, and CLOSES AGAIN when revs/load drop back down.
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Originally Posted by jeremyc74
Mine seems to be open, and it stays that way for the first few minutes after I start the car. The idle is pretty loud for a few minutes, then quiets down to normal. I'm thinking it takes a second for the vacuum to build, but it may be a function of how they're controlling the valve.
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The car isn't loud for the first minute or two because of the flap... in fact, you can hear the flap close right after you start your car. It's just loud because the engine is warming up (or something similar, I'm not really that educated when it comes to BMW engines, someone else care to chime in?).
For those who want to see it, the flap pivots on a vertical axle in the center of the left exhaust pipe, about 8-10" in. It rotates 90 degrees from a closed to open position. Stand outside your door, start your car, and run back quickly to hear/see it close.