Hallo!
Does somebody have any information about flap in exhaust of BMW 535d? How is it working? It is seen that flap is opening/closing during the driving. Why is this flap there anyway? Thank you for INFO.
Best regards from Slovenia,
Klemen

 

It is the same as the flap on my 330iS. At lower revs it is shout to keep noise down when you drive hard the flap opens to let the exhaust escape quicker and typically the noise doesnt matter becuase your on a road away from built up areas. It is needed to comply with legislation. If you want a sportier sound, you can disconnect the vaccum pipe (plug it with a golf tee) and the flap stays open all of the time...did theis on my 330 sounds great didnt see any improvement or degradation of performance however

 

I was following my wife driving my car the other day and thought I saw a flap in the exhaust but paid no attention. Your post just reminded me. Thanks for the info. Better get rid of car before exhaust needs replacing as that looks well cheap, NOT.

 

Its on the 545 exhaust too not sure about the 525 and 530 but I think I remember reading some said it wasnt a good idea to keep it open all the time... I forget why. Maybe I'll do a search later and find out.

 

The valve works with the engine inlet vacuume on older engines, and through a vacuume pump on the newer 6 cylinder engines

It closes at low engine speed to reduce noise, thats all it does

Its a very simple little device, and if you put a different exhaust on you just remove the vacuume line and plug it ( teh oem sport exhaust for the E46 makes you do that )

 

Is it normal that it makes a "cling" noise when it opens or closes?

 

My wife moved my car earlier and I took a quick look at the exhaust flap. On start up I noticed the flap stayed open on tickover and during a gentle reverse at low revs. I thought it was supposed to be closed at low revs! Is mine not working correctly?

 

I suppose your is working properly...
But that's why I can't still understand its function.

I saw yesterday an 535d on an highway, I was behind it and i saw that when the car accelerated the valve closed and the opposite happened in braking or spped lowering conditions...

I studied engines for years but i can't give an exact explication about it. It seems the web don't knows about it!

Bye bye

 

That looks like rust at the end of the tips

 

Could it not be to increase back pressure during increased revs to prevent flat spots and it opens and closes in order to increase fuel efficiency and performance? <_<