Exhaust flap

[JPMD]

Was thinking about getting exhaustmeister to get a little more sound out of my comp pkg exhaust. The car is leased and I anted up the extra cash for it so although I love some of the aftermarket exhausts I wand to stick with what I have. Also considered Turner but allot of people are switching out because I guess of drone etc; also what scared me is the "temporary" power losss issue even with those who plugged there vacuum lines.

Anyway I was just trying to figure out how and when the muffler exhaust flaps worked. (Also see explanation found on older 2007 post obviously not F10 M5 but BMW)

I would agree with the below explanation but when I looked today I noticed some differences. After using the car earlier today I restarted it about 30min later (engine still very warm) and the valves were OPEN. Also thinking about things every time I get out of the car (notice it most when coming home parking in my garage quiet and has some echo) a noise after shutting the engine and exiting quickly toward the back of the vehicle which sounds like the valves closing. This means they were open even while I was driving below 2500-3000 RPMs i.e. entering the driveway/garage and coming to a stop.

I'll check in the am during cold start (not to cold in FL) to see if they are open or closed but could swear the last time I checked at cold start they were closed.

Any insight into this. Is there a difference for comp pkg cars? Also most of the time I keep my M settings sport plus throttle, sport steering and suspension and level 2 for DCT. Not sure if this controls it.


Prior Post:

Do a search. It is mentioned in BMW training.

It is to reduce noise at low RPMs.

For an E46 but here you go: http://autorepair.about.com/library/a/1d/bl104d.htm

The electrical function of the exhaust flap operation is controlled by the MS 41.1 module.

At idle speeds, up to 2500 RPM: the exhaust flap is closed with vacuum applied to the actuator. This causes the exhaust gas to pass through the long resonator pipe, reducing the low frequency noise that is generated.

Above 2500 RPM: the exhaust flap opens. This allows the exhaust to pass through the short pipe which maximizes the back pressure effect to provide the best performance.

In the event of electrical or vacuum failure the flap will rest in the open position providing maximum exhaust throughput.

Therefore plugging the pipe simulates a vacuum failure and provides max back pressure.

It's for noise reduction. Specifically low frequency resonance at low RPMs that some less informed 'near-luxury' car drivers may not be too keen on. Not all 3 er owners want to cut the zorst off at the headers like us

Golf tee it and the car sounds great at idle.

[M5TXGuy]

They open about 1 minute after the rpms drop after a cold start. They stay open for a long time after you turn the engine off. They only close when the engine cools off enough to require a new cold start.

[M54ccibo]

I have always wondered about the valves myself. I noticed a different amount of soot on each tail pipe, less on the outboard...where the valve resides. Wanted to see if there was a difference I wired my Akra valves open. Definitely louder below 3K, short of visual proof I'd say the valves do open/close when driving. FWIW, I drive my car with engine set to sport plus 100% of the time.

[JPMD]

Originally Posted by M5TXGuy

They open about 1 minute after the rpms drop after a cold start. They stay open for a long time after you turn the engine off. They only close when the engine cools off enough to require a new cold start.

Originally Posted by M54ccibo

I have always wondered about the valves myself. I noticed a different amount of soot on each tail pipe, less on the outboard...where the valve resides. Wanted to see if there was a difference I wired my Akra valves open. Definitely louder below 3K, short of visual proof I'd say the valves do open/close when driving. FWIW, I drive my car with engine set to sport plus 100% of the time.

Thanks guys.
This is what I have observed thus far today.

Pre start this morning valve closed
Immediately after cold start valve closed even after setting my "M-mode"
20 min drive to work exited car in the lot while still running and the valves were opened
Shut of ignition and valves closed

will keep you posted on developments.

Seems however so far they are closed only during warm-up for cold engines. Some have stated to help perhaps the engine and catalytics get up to temp quicker.

I had concerns with maybe wiring them open permanently because others have stated they assist with adding back pressure at low RPMs for more torque and open on heavy acceleration after a certain RPM to decrease backpressure and increase HP. Others had stated they are purely for sound control at low speeds. After todays observation these last 2 statements cant be true since after my car warmed up the valves remained open all the time up until the engine was shut down and the noise I hear exiting the vehicle toward the rear is I believe the valve closing.

My only other concern would be if I had a faulty vacuum line or something else that is causing the valves not to operate properly.

Anyway as long as everything is working correctly I guess the only benefit to the Exaustmeister with respect to adding more sound will be extending the morning cold start and initial drive

[M54ccibo]

Originally Posted by JPMD

Thanks guys.
This is what I have observed thus far today.

Pre start this morning valve closed
Immediately after cold start valve closed even after setting my "M-mode"
20 min drive to work exited car in the lot while still running and the valves were opened
Shut of ignition and valves closed

will keep you posted on developments.

Seems however so far they are closed only during warm-up for cold engines. Some have stated to help perhaps the engine and catalytics get up to temp quicker.

I had concerns with maybe wiring them open permanently because others have stated they assist with adding back pressure at low RPMs for more torque and open on heavy acceleration after a certain RPM to decrease backpressure and increase HP. Others had stated they are purely for sound control at low speeds. After todays observation these last 2 statements cant be true since after my car warmed up the valves remained open all the time up until the engine was shut down and the noise I hear exiting the vehicle toward the rear is I believe the valve closing.

My only other concern would be if I had a faulty vacuum line or something else that is causing the valves not to operate properly.

Anyway as long as everything is working correctly I guess the only benefit to the Exaustmeister with respect to adding more sound will be extending the morning cold start and initial drive

Mine appeared to work like yours, always being opened after warm up. Exit car idling, etc. But it wouldn't explain the additional soot on the outboard pipe, as well as a difference in tone while under 3K RPM with them wired open. Dunno?

I think the best bet is for me to put my GoPro up under the rear end to video the actuator. I was going to do this a year ago but never got around to it.

RE: back pressure and lost performance, I don't know about that...my butt-o-meter says things are exactly the same

[JPMD]

Originally Posted by M54ccibo

Mine appeared to work like yours, always being opened after warm up. Exit car idling, etc. But it wouldn't explain the additional soot on the outboard pipe, as well as a difference in tone while under 3K RPM with them wired open. Dunno?

I think the best bet is for me to put my GoPro up under the rear end to video the actuator. I was going to do this a year ago but never got around to it.

RE: back pressure and lost performance, I don't know about that...my butt-o-meter says things are exactly the same

The GoPro is a great idea.

I agree not buying the back pressure theory; at least not for this particular situation. Back pressure is important in some instances however i.e. I have a Boxtser Spyder with obviously much less torque and HP than my M5 beast with BMS tune. Since also its a N/A engine putting on catless headers has decreased low end torque which you would feel with real world driving especially since its not that torquey of a car. There is however more HP at the top of the RPM range for the track guys.

I think with our cars significant power loss is felt when the vacuum lines are not plugged although guys with Turner Exhausts have had it happen even when plugging the lines but then report that it spontaneously resolves.

[JPMD]

This is interesting

http://www.insideperformance.de/onli...37/language/en

much more expensive than exaustmeister but they claim can be controlled by hitting M button which is nice

on the webpage it states that when not activated it will behave similar to OEM and specifies valve will open under kick-down, higher RPMs and prevent over heating

So probably the valve is for noise control at idle especially cold start and the reason we see it open at idle after using the car for a while is the valve opens to manage temperature. Just a theory based what has been posted and reported

[soooma]

I have been enjoying exhaust meister for a few months now and let me say that I have never ever since my car with valves closed since!! Because the difference is very very noticeable and to me it will be better bang for you Mr buck to just hard wire them open and I am sure you won't regret it!! Unless you lie the idea of control which is fun sometimes when you're at the dealership or with some friends and want to have fun -

[JOHNBMWM5]

Originally Posted by M54ccibo

I have always wondered about the valves myself. I noticed a different amount of soot on each tail pipe, less on the outboard...where the valve resides. Wanted to see if there was a difference I wired my Akra valves open. Definitely louder below 3K, short of visual proof I'd say the valves do open/close when driving. FWIW, I drive my car with engine set to sport plus 100% of the time.

I agree they must be closed a lot, I wired mine open and the sound is much better all the time.

[JPMD]

I installed the exhaust keister this weekend. I'm not the handiest guy in the world but the install was very easy. The instructions and diagrams on the website are excellent. It works as advertised. I was also able to program the buttons on the mirror using the remote.

Its no way near some of the more aggressive after market exhausts but I can definitely hear a difference after opening the valves during cold start and driving at lower RPMs.

Thinking about resonator delete like sooma but might hold off for now as I'm also considering DPs which if I go that route I probably would not delete the resonators.

I've experienced no loss of power at all. Do not usually pay attention to MPG so can't comment on that.

[JPMD]

Love you guys and this forum!

By reading some of the other recent threads and posts it appears that the Comp Pkg has a much less restrictive or no resonator at all.

Saved me a few buck and some embarrassment of having a pipe cut and replacing it with another pipe.

[ShainoF10M5]

I made this mod about 4 months ago after owning the car for almost a year. I can say with 100% certainty that the car sounds a few notches meaner at all times. I highly recommend it.

[JOHNBMWM5]

Originally Posted by JPMD

Love you guys and this forum!

By reading some of the other recent threads and posts it appears that the Comp Pkg has a much less restrictive or no resonator at all.

Saved me a few buck and some embarrassment of having a pipe cut and replacing it with another pipe.

Add to it by wiring open the valves, you can hold the valves open with a 1" shaved down broom stick then use alloy wire 3mm and wire them, it's easy and if you don't like it just cut off the wire.

[Lual]

Originally Posted by M5TXGuy

They open about 1 minute after the rpms drop after a cold start. They stay open for a long time after you turn the engine off. They only close when the engine cools off enough to require a new cold start.

Silly question:

If the valves are much noiser when they are open, how can be that the car is much noiser at cold starts (i.e. When the valves are closed)?

Thanks,

[M5TXGuy]

Originally Posted by Lual

Silly question:

If the valves are much noiser when they are open, how can be that the car is much noiser at cold starts (i.e. When the valves are closed)?

Thanks,

On a cold start, the car revs much higher before winding down. The car is only louder because the higher RPMs on a cold start.

Ill also say that I have been paying more attention to the valves after this thread. Most of the time the valves stay open when I shut the car off, but occasionally, they will immediately close. I can't figure out why that happens.

[JOHNBMWM5]

I have taken the wire off the Valves, ready to part exchange the car in a month or so time, been looking at the exhaust pipes, and only one is getting dirty now, the inner one, the outside one is as clean as new.
This tells me it's shut a lot.
I drive in Sport+ all the time also.
So europe (UK) cars can't be open all the time if the two exhausts are two different colours IMO. Mystery .

[JPMD]

Originally Posted by JOHNBMWM5

I have taken the wire off the Valves, ready to part exchange the car in a month or so time, been looking at the exhaust pipes, and only one is getting dirty now, the inner one, the outside one is as clean as new.
This tells me it's shut a lot.
I drive in Sport+ all the time also.
So europe (UK) cars can't be open all the time if the two exhausts are two different colours IMO. Mystery .

After more research and observation I have a feeling Europe and USA cars work the same.

I think the flap is either intended strictly for sound control and is indeed controlled by RPMs and flow vs as others have stated to help the catalytics heat up faster.

If the sound theory is correct then there is more to it because after the engine is up to usual operating Temps; certainly after some aggressive driving the valve stays open even under low RPMs. On the European site that has a device that can keep the flap open using the M button they comment that the flap open under kick down and high RPMs which we already know but they suggest or state they may be to manage heat. ie stay open to regulate or prevent engine overheating.

Unfortunately I'm not an expert by any means just trying to logically try to come to some conclusions.

So on the other hand those that state it's related to the catalytics heating up faster on cold start may be correct because this is usually the only time my flaps had been closed prior to my exhaustmeister

What I may try and do is start and operate the car over the weekend and try to stop before the engine fully heats up check the valves while it's running then repeat the process when it just gets up to temp.

[M5 RAG]

I pondered this one for a long time, like most here I didn't fully appreciate how often the valves where closed while driving, as John noticed, it was the soot levels on both the inner pipes that confirmed it for me.

I was (daftly) looking at the flaps when the car was idling (warm) and they where always open so I initially assumed they where always opened after cold start but they are way more active than that, in fact when driving they are constantly opening and closing, in my opinion they close the minute car drives and the revs climb past idle, they are then closed from about 1000rpm to 3000rpm and then only open at warm idle or above 3000 (ish) rpm, when you think about it, in normal traffic situations the car is in this 1k to 3k rpm range a hell of a lot, hence the sooty inner pipes.

I eventually worked this out and wired the flaps open, this gives an appreciably enhanced exhaust note at the low to mid rev ranges mentioned above.

I hope someone out there does the GoPro thing and proves my theory.

As John states above, wire the flaps open, cost me about £1 for the lock wire and it can be removed in seconds.

[JPMD]

Originally Posted by M5 RAG

I pondered this one for a long time, like most here I didn't fully appreciate how often the valves where closed while driving, as John noticed, it was the soot levels on both the inner pipes that confirmed it for me.

I was (daftly) looking at the flaps when the car was idling (warm) and they where always open so I initially assumed they where always opened after cold start but they are way more active than that, in fact when driving they are constantly opening and closing, in my opinion they close the minute car drives and the revs climb past idle, they are then closed from about 1000rpm to 3000rpm and then only open at warm idle or above 3000 (ish) rpm, when you think about it, in normal traffic situations the car is in this 1k to 3k rpm range a hell of a lot, hence the sooty inner pipes.

I eventually worked this out and wired the flaps open, this gives an appreciably enhanced exhaust note at the low to mid rev ranges mentioned above.

I hope someone out there does the GoPro thing and proves my theory.

As John states above, wire the flaps open, cost me about 1 for the lock wire and it can be removed in seconds.

Nice write up thanks.

The only thing is that after driving my car for a while each time I exit the vehicle I can hear the flaps close so I'm assuming they are open just before shutting it down.

So the valve is open at idle when warm , closed at cold start, closed rpm 1000-3000 and open at higher RPM?

Think we need the GoPro for this one.

[M5 RAG]

Originally Posted by JPMD

So the valve is open at idle when warm , closed at cold start, closed rpm 1000-3000 and open at higher RPM?

Yep thats my take on it.

Would love to see it in action to prove this though!

[Lual]

Originally Posted by M5TXGuy

On a cold start, the car revs much higher before winding down. The car is only louder because the higher RPMs on a cold start.

Ill also say that I have been paying more attention to the valves after this thread. Most of the time the valves stay open when I shut the car off, but occasionally, they will immediately close. I can't figure out why that happens.

I think this is not totally right
At cold start, the car revs up to 1.500 to 1.800 aprox and you get this great sound.
When is already warm, and revs go down, the sound reduces.
But at normal use, if you rev up to same rpm, you dont get the same sound as when warming up. So high rpm are part of the reason, but not the only one.

[M54ccibo]

Originally Posted by Lual

I think this is not totally right
At cold start, the car revs up to 1.500 to 1.800 aprox and you get this great sound.
When is already warm, and revs go down, the sound reduces.
But at normal use, if you rev up to same rpm, you dont get the same sound as when warming up. So high rpm are part of the reason, but not the only one.

That's correct. I believe I read somewhere that engine timing is also different on cold start, which changes shortly after the revs decrease. With the valves wired open now I can hear the three phases:

- Cold start timing and revs (loudest)
- Cold start timing (loud)
- Normal Idle (normal)