Exhaust active noise control valve

[johntclark]

I have read other forums and can't explain why my valve is open while at idle. How is there that much pressure in the pipe to open the valve at idle. FYI it does close when I turn the car off, so it is working. Anyone know what's up?

[mr-karim]

http://www.ebay.com/itm/231067201069...ewitem&vxp=mtr

Check this out

[johntclark]

That did not help too much. Any body else ?

[F12M6MD]

http://www.realoem.com/bmw/showparts...99&hg=18&fg=20

Yes the exhaust valve works off vacuum pressure but it is controlled electronically via #1 in above schematic. If yours is remaining open at idle even when warm you may have some trouble with #1. That's my thought.

[GreyCoupe]

It is working properly. The valve opens on cold starts to create the aggressive sound, then closes to accelerate heating the catalytic converters to operating temperature.

Many jerry-rig these valves to keep the flap open, sustaining this rich exhaust note. My sense is the responder thought that controlling this exhaust valve was what you sought to do. What MrK sent you is the most sophisticated way to do this, while permitting the driver to close the flap remotely, and return to stealth mode.

Other "fixes" tie wrap the flap valve actuator, holding the valve open.

[JOHNBMWM5]

I wired mine open after a few miles of checking and the Cats do NOT warm up slower , just the same time frame, but the sound is better all the time.
Here the Flap closes (from memory) under 3K rpm then opens or if in sport or sport+ it stays open.

[GreyCoupe]

I have not measured cat converter time-to-temperature flap open versus flap closed personally.

Other drivers have told me this is what the flap actuator is designed to do, in order to reduce emissions. Sounds logical to me. Surely don't know what other purpose this contraption serves.

[johntclark]

Grey, the flap actually remains closed at cold start for a bit until there is negative pressure at idle. Due to this the flap rattles against the shut position's frame. Once the pressure is reduced as the bore is still closed the flap opens stopping the sound. Unfortunately the Eisenmann Exhuast system still can't seem to figure this out. Sounds like crap on start up. Very embarrassing. Stay away from this system. I have worked with Jesel at IND and while he is quick to respond the issue still is present. After three systems exchanged I am convinced this annoying cold start flap is just part of the system.. Not happy at all. If anyone wants a sound clip to help with their decision I am happy to send you a few clips. Just pm me.

[JOHNBMWM5]

Originally Posted by GreyCoupe

I have not measured cat converter time-to-temperature flap open versus flap closed personally.

Other drivers have told me this is what the flap actuator is designed to do, in order to reduce emissions. Sounds logical to me. Surely don't know what other purpose this contraption serves.

It's just "Noise control" in urban environments.