[Crystal330i]

Hey everybody, I've had my 340i muffler on my car for awhile now. Just wondering, is the valve supposed to flip open during a cold start, or if I'm in Sport+ mode? I was under the assumption that it should be, but I just found out that the valve never opens on cold start, and if I switch to Sport+ and rev it, it doesn't open either. After taking the car on a hard drive in Sport+, I got home, parked it, shut the engine off and went to look at the valve - now it's open. So it opened sometime during the drive and didn't close... weird. Turned the car back on and the valve immediately flipped back to closed.

Is this normal? And if it isn't, what can I do to fix it? It's not stuck or anything since it opened during the drive, but maybe it's a coding issue or something.

[bimmer456]

It is closed until the exhaust temperature reaches a level that allows the catalytic converter to work efficiently. Then it opens in sport or sport plus or above 4k rpm in comfort. If you shut it off in sport it will remain open but close when you start it back up until exhaust temps are reached again. If it’s closed and you put it in sport it will be closed initially even if warmed up until you tap the throttle.

[Crystal330i]

Originally Posted by bimmer456

It is closed until the exhaust temperature reaches a level that allows the catalytic converter to work efficiently. Then it opens in sport or sport plus or above 4k rpm in comfort. If you shut it off in sport it will remain open but close when you start it back up until exhaust temps are reached again. If it’s closed and you put it in sport it will be closed initially even if warmed up until you tap the throttle.

I see. Great explanation, thank you!