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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > Why is My Exhaust Butterfly Valve Permanently Open! BMW E90



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      10-07-2010, 09:25 PM   #1
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Angry Why is My Exhaust Butterfly Valve Permanently Open! BMW E90



I checked my exhaust valve several different times, when the car was off, cold idle, warm idle, etc.. it is always open. Anyone know what I can do to find out what the problem could be?

Also, how is the butterfly valve suppose to act? Is it suppose to be closed until 2500 rpm? Closed until 50% throttle? Anyone know?

I know people like doing the golf tee mod, but I just like everything on my car to function like BMW made it to. So closing and opening at the correct times would be just fine with me

Thanks guys, much appreciate any help with this...
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      10-07-2010, 09:55 PM   #2
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2 things that may be simple but might have been overlooked

1) is the rubber vacuum line connected?

2) there is a connector in the trunk behind the driver side rear taillamp. if its disconnected, the butterfly valve remains open.
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      10-07-2010, 11:10 PM   #3
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I'm going to take a shot in the dark that it's supposed to stay open. The butterfly was installed on your car primarily to allow the DSC to function (also as a failsafe, I think).
Remember the valvetronic controls your throttle on that car. I would imagine it stays open to reduce pumping losses (which is one of the original premises of Valvetronic).

That's my guess...
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      10-08-2010, 04:29 AM   #4
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On the 330i it's supposed to stay open on idle. It closes when you drive, but I'm not sure the exact conditions.

The 335i closes it at idle.
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      10-08-2010, 05:49 AM   #5
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I thought that was for the catalytic converters so they get up to operating temp faster....far from sure though.
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      10-08-2010, 10:46 AM   #6
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Uhhh.... it has a VACUUM line, so under heavy VACUUM it should shut (ie. in gear during deceleration....) which means you can't see it shutting at idle or when the car is off. I think it's to help prevent afterburn or something.

You'd have to strap a camera to the bumper and then drive it up to 25mph in 1st gear, then let off the gas while leaving it still in gear, then review your footage
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      10-08-2010, 10:51 AM   #7
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On the 330i, if you look while the car is stationary, it will seem like it is always open. When you drive, do you get much more soot on one tailpipe versus another? No doubt, you do. The cleaner one is the one with the butterfly valve. It closes from time to time while moving, presumably to alleviate exhaust noise while cruising.
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      10-08-2010, 10:52 AM   #8
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this is very insightful! Thanks I had the same question!
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      11-05-2010, 02:32 PM   #9
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Nice! So basically there is nothing wrong and it is acting as it should. I went all OCD for nothing

p.s. i think the 325i and 335i butterfly flaps act differently than 330i
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      11-05-2010, 02:46 PM   #10
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i've always had the same question but during deceleration i would hear a rattle from the flap. I unplugged the connector and now i dont have to worry about rattles.
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      11-05-2010, 03:40 PM   #11
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My butterfly valve is always open at idle but then closes if I accelerate moderately to alleviate exhaust noise at the mid-level RPMs. If I accelerate quickly it stays open the full way. My exhaust note is quite noticeable at idle. I am still waiting to get performance exhaust on the next one.
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      07-07-2014, 02:00 PM   #12
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Quote:
Originally Posted by E90aL View Post
i've always had the same question but during deceleration i would hear a rattle from the flap. I unplugged the connector and now i dont have to worry about rattles.
(my car is a 2006/2007 BMW 130i with barely 52.000km/32.000miles on the "clock")

I really believe I have this noise... So I went on to check the butterfly valve... It was open at idle, so I thought something was wrong with it, but ruled out the noise coming from it since it is "always open" (I thought it was stuck!)

Then I found this thread and now I believe the rattle comes from the valve since I can hear it at low RPMs, with only the windows open. If I keep playing with the gas pedal the rattle becomes crazy, if I keep a strong, or even constant acceleration it is gone/barely noticeable. Anyway, after 2500rpm there's no rattle anymore...

Can anyone put a picture of the connector I have to unplug for it to stay always open? Or will I have to resort to some GO-PRO footage from my exhaust?

(I even took a video of it, but I guess it is a useless video:

Last edited by loudenvier; 07-07-2014 at 02:09 PM..
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      07-07-2014, 04:07 PM   #13
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Thread revival!
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      07-07-2014, 04:15 PM   #14
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Quote:
Originally Posted by v1nc86 View Post
Thread revival!
Sorry for that! I didn't even checked that date of the last post... It was relevant to me now though If I get to make the "GO-PRO" video I'll behave like a necromancer once again and revive this thread!
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