Good Ole exhaust flap

[dozanti]

Heres one for you, and its related to the OLe' exhaust flaparoo. What operates the exhaust flap. Now hold on a second, I know theres a vacuum line, and a one way valve off the manifold to the canister, but my problem is it never opens. So my question is, how does the electric valve in the trunk supposed to work. We applied 12vs to it and it clicked shut. Would a faulty temp sensor cause this, because this valve was getting wicked hot (hooked up the way it should be). Something has to send it signal to open and close, hence open valve and shut at op temp and rpm. I had a temp sensor on order but they seem to have messed things up, so as for now it is not in. (BTW I got code "34" from my bavarian reader saying "exhaust flap")

[richardodn]

The exhaust flap valve receives power from fuse 50. Ground is provided through pin 52 of the DME. I'm not certain exactly what the DME uses to calculate when to ground that pin but I believe it's RPM based. I think it opens at around 3000 RPM. Have you done electrical tests at the valve? The Red/White/Yellow wire should have power at all times and the Gray/Violet wire should show ground at RPMs above 3000. (Maybe other conditions?) Fuse 50 also provides power to the carbon canister valve.

[dozanti]

I take it the electric valve shouldnt get extremely hot ( anything electrically with common sense ). I will recheck the wires with a test light, but it does receive power im just not sure on which ones. So it could possibly be the pin 52 or the valve itself correct?

[99323iconv]

Its purpose is to help the engine heat quicker by restricting the exhaust (that is why it revs so high at slow speed when engine is cold). Once the engine heats up some the flap will open thus lowing the exhaust pressure and high rpms. I believe it is controlled by temp sending unit and/or O2 sensor.

Hope this helps.

[dozanti]

okay, well its officially confirmed, it does not open after warming up or rpm. So i will buy the coolant temp sensor and hope all goes well. I may replace the electric valve in the trunk, it was wicked hot when i got to it

[richardodn]

Its purpose is to help the engine heat quicker by restricting the exhaust (that is why it revs so high at slow speed when engine is cold). Once the engine heats up some the flap will open thus lowing the exhaust pressure and high rpms. I believe it is controlled by temp sending unit and/or O2 sensor.

Hope this helps.

Huh?

The flap is RPM controlled. The muffler has 2 internal paths. The unrestricted path is serpentine and is used to reduce noise at typical operating RPMs. At higher RPMs when maximum performance is desired, the flap open allowing flow through a second straight path.

[MJFX328]

okay, well its officially confirmed, it does not open after warming up or rpm. So i will buy the coolant temp sensor and hope all goes well. I may replace the electric valve in the trunk, it was wicked hot when i got to it

Honestly your spending money on a worthless investment. Swap an M3 or aftermarket exhaust and call it a day. Or break it like most people do. Either way it wont make much difference. Focus on maintenance.

[richardodn]

okay, well its officially confirmed, it does not open after warming up or rpm. So i will buy the coolant temp sensor and hope all goes well. I may replace the electric valve in the trunk, it was wicked hot when i got to it

You're right, it should not get wicked hot. I'm trying to figure out how the DME could detect problems with the exhaust flap to throw the code. The circuit goes like this: +12V -> Valve -> DME -> ground. There are only 2 things it could be measuring; voltage (actually voltage drop over the valve) or current flow. In either case it would see the valve running electrically out of spec. I'd start by replacing the valve and verifying there is vacuum at it.

I'm pretty sure that the flap has nothing to do with restricting the exhaust so the engine heats up faster. Maybe something like that would help the cats heat up faster. If that were it's purpose, the tailpipe is a silly place to put the restriction. Besides, the flap would then be part of emission controls and replacement parts would be required to implement it or specify it as off-road use only.

Honestly your spending money on a worthless investment. Swap an M3 or aftermarket exhaust and call it a day. Or break it like most people do. Either way it wont make much difference. Focus on maintenance.

You do realize that some people like all their systems working correctly.

[dozanti]

You're right, it should not get wicked hot. I'm trying to figure out how the DME could detect problems with the exhaust flap to throw the code. The circuit goes like this: +12V -> Valve -> DME -> ground. There are only 2 things it could be measuring; voltage (actually voltage drop over the valve) or current flow. In either case it would see the valve running electrically out of spec. I'd start by replacing the valve and verifying there is vacuum at it.

I'm pretty sure that the flap has nothing to do with restricting the exhaust so the engine heats up faster. Maybe something like that would help the cats heat up faster. If that were it's purpose, the tailpipe is a silly place to put the restriction. Besides, the flap would then be part of emission controls and replacement parts would be required to implement it or specify it as off-road use only.



You do realize that some people like all their systems working correctly.

Yes I would like it to work correctly, so when it is I can PASS EMISSIONS. I have a feeling the temp sensor is sending inaccurate readings to the ecu there for my fuel/air is rich. I keep getting p0420 (below efficiency 1-3) but i find it hard to believe a new control smog pump valve, all vacuum lines replaced, new high flow magna flow cat, o2 sensors twice, new CCV, new plugs (4 times because Ive been finding different live data with all, and some drop my NOx and some drop my HC), and the list goes on would be giving me this. This has to be something simply small and stupid. I will go on to the electric valve. I do have vacuum to it also. Im just stumped, and everyone I turn to has no idea, dealer ship or repair ase certified shops (ive called a few) . Some days I feel like setting it on fire and roasting a marsh mellow or two on it ...... but then I start it and take off and wonder why I'd ever do such a thing haha I love my car.

[richardodn]

Some days I feel like setting it on fire and roasting a marsh mellow or two on it ...... but then I start it and take off and wonder why I'd ever do such a thing haha I love my car.

In a nutshell, that's what it means to be a BMW owner.

[visible]

I am dead confident when I say there's been a thread with someone very stubborn on a quest to find out what the true purpose of the flap was.

He went as far as contact a North American BMW rep and receiving an official answers. It had nothing to do with performance, nothing to do with heating up the exhaust.

The sole purpose was to change the note to something more pleasant sounding to luxury segment buyers.

[dozanti]

Thats been established..........
You are not reading my entire posts. Im having two problems, emission and the flap simply ISNT working (opening/closing). I have been discussing it with several members trying to see if the temp sensor is in fact a dual purpose, what controls the flap (not what its for). If this is the case then that would explain rich fuel mixture because the computer thinks the car is cold and also the flap will not work. I even got an engine code for the flap. The electric valve in the trunk gets really hot and this isnt normal, and it concerns me.

[MJFX328]

You should try unplugging the "valve", not 100% sure what your referring to.

Calling shops wont solve the problem. Take it into a reputable place.

[dozanti]

lol its been unplugged ! I have perfect vacuum to it. You put it on (line) it shuts the valve, you unplug it and it opens. The electric valve when unplugged to test continuity throws my CEL (its already on, but throws a code).

[imbiling]

Hello. I have a E46 with the same issue. The exhaust flap is not closed by the DME. Everything is working as it should be. The vacuum lines and the electric valve are fine. I can close the flap in INPA, but it doesn't close while I am driving.

Sent from my Nexus 5X using Tapatalk

[shogun]

you should better post your problem in the E46 forum.
Here similar threads
https://www.bimmerforums.com/forum/s...ctor-Flap-quot
https://www.bimmerforums.com/forum/s...m-Line-Routing
E46 flap stuck open
http://www.bimmerforums.co.uk/forum/...k-open-t69606/
https://www.bimmerforums.com/forum/s...lap-Stuck-Open
from bavauto:
BMW 3-Series Exhaust Muffler Flap Valve – Stuck, Noisy – E36, E46, E90, E91, E92, E93
This answer is applicable for many BMWs in addition to the one listed below.
Q
2006 330i
My question to Otto is in reference to the exhaust butterfly valve in the right tailpipe of my 2006 BMW 330I. The valve rattles excessively at idle, so noisy that it can be heard inside the vehicle with the windows closed. I took the car to the dealer who stated that this was a common problem and sprayed the valve assembly down with WD-40 (which of course did absolutely nothing to correct the problem). After returning the vehicle to the dealer, he stated he would have to troubleshoot the problem and would cost $$$$$$. I was thinking that if this is a common problem, there should be a common fix! My question to you is 1). what is the purpose/function of this valve and 2). What can be done to correct the rattling at idle. It does not appear that the valve can be replaced without replacing the entire muffler/tailpipe assembly. The vacuum line to the valve is connected securely. I did not see this problem anywhere in earlier blogs. If I have overlooked it, my apologies. Any help you could provide to help solve this problem would be much appreciated. P.S. I know I could disconnect the vacuum line to fix the problem, but would like to have the valve functional (but quiet) if possible.

A
BMW has used the vacuum operated exhaust valve on various models. Most notably, many of the 6-cylinder 3-series models from 1996-on. The valve is intended to decrease exhaust sound (noise) at lower engine RPMs, by routing the exhaust flow through a longer (and more baffled) path inside the muffler. At engine speeds above a specified RPM (such as 2500 RPM), the engine management system opens the valve which allows a free-er exhaust flow through the muffler, assuring full engine power.

We have never seen these valves stay functional for the life of the muffler. Typically, they corrode and/or rust and freeze up. Since your valve is rattling, it may not be frozen up, but may have a worn shaft or the vacuum control unit may be faulty (more on this, below).

In testing these units, remove the vacuum line from the valve and test as follows:

* At rest, the valve should be open (engine off, or vacuum line disconnected). If it is not open, either the vacuum actuator is stuck or the valve itself is stuck and/or seized due to rust or corrosion, likely.

If the valve is not stuck closed, to begin with, continue testing:

* At idle, the vacuum line should show vacuum (using a simple vacuum gauge), this would be when the valve should be closed. If no vacuum, there is a problem with the vacuum system and further diagnostics will be required. If there is vacuum at idle, rev the engine past 2500 RPM or a bit higher (not all models are set to open at 2500 RPM, some may be higher …. get the RPM up high, but don’t just bounce it off the rev-limiter). You should see the vacuum go away at some point (this is when the valve would open). If you do have the initial vacuum, then this part of the test should show proper function as well.

* Using a vacuum gun (such as a basic Mity-Vac tool), apply vacuum to the valve control unit. The valve should close. If the valve does not close, either the vacuum actuator is faulty or the valve is stuck open.

In the case of a faulty vacuum actuator or stuck valve (or rattling valve), these parts are not available separately (they are part of the muffler assembly). If the valve is non-functional, it would be preferable to have the valve always open as opposed to always closed. A rusted valve assembly can often be forced open or the flap can be bent to allow the pipe to be open. We really do not have an operational fix for a loose or rattling valve. Perhaps the valve flap could be spot welded in the open position, to prevent the rattling.
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As the originator of this blog, I performed the vacuum tests as you suggested and determined the valve itself was the culprit. Replacing the muffler is a high dollar solution. The easiest fix was to disconnect and plug the vacuum line to the valve which allows the butterfly to remain (springloaded)open. The exhaust note is still quite pleasant at lower engine RPM’s without the rattle.
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Hello, i have a 1996 328i a. And I have the following problem. My exhaust flap valve does not open when you its suppose to. Engine off, the valve is open. Turn the engine on and it will close normally. But if you rev the engine up it stays closed. I’ve just bought the car and noticed that there was an alarming noise of a high pitch from the tail pipe in high revs probably due to de valve being closed in high revs. So to use the car wile I try to find the solution I’ve left it open by removing the electrical plug of the solenoid on the trunk of the car. Can you help
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It would seem that the vacuum solenoid valve is staying open and applying vacuum at all times. The solenoid valve should have voltage applied and be allowing vacuum to the flap actuator at idle and low engine speeds (when the muffler valve should be closed) and then should be unpowered when the flap should be opened (closing off the vacuum and opening the flap).
The solenoid valve receives 12-volts directly from the ECM (Engine Control Module) relay and then the power goes to the ECM, where it is either left open, (no power flow through the valve, valve is closed and the flap is open) or grounded (power flows through the valve to ground, the valve opens and the flap is closed). If unplugging the power from the solenoid valve allows the flap to open, then we would think that the solenoid valve is working properly and that the power to the valve is at fault (always supplying power). If this is the case, there may be a grounding short in the wire from the solenoid to the ECM, or the fault is in the ECM. You can’t do any harm by leaving the solenoid unplugged, and the valve open.
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Otto, your a ledgend. After many years of hearing this rattle I’ve just unpluged the vacuum line and noise has stop. Cabin noise is still the same. Love the e46 330i.

[jmo69]

Strictly noise abatement, both of my cars have the infamous golf tee mod, gave my e46 a subtle rumble and still quiet in the cabin. I assume my e36 sounds the same, but I don't get to hear it coming up the driveway.