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      04-25-2021, 12:30 PM   #1
vetteflier
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Fuse to keep exhaust baffle open?

Just got my '21 M4 Competition and love it! In my Corvettes, there was a fuse you could pull to keep the exhaust baffle open at all times. Is there one in the M4? First time BMW owner, really enjoy the forum and information. Lots to learn!

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      04-25-2021, 12:54 PM   #2
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Quote:
Originally Posted by vetteflier View Post
Just got my '21 M4 Competition and love it! In my Corvettes, there was a fuse you could pull to keep the exhaust baffle open at all times. Is there one in the M4? First time BMW owner, really enjoy the forum and information. Lots to learn!

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On the older F8X, you could simply unplug each of the 2 valve controllers near the exhaust and that would leave the exhaust flap open at all times. Might be similar for the G8X - not sure!
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      04-25-2021, 09:25 PM   #3
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Quote:
Originally Posted by Sbm007 View Post
Quote:
Originally Posted by vetteflier View Post
Just got my '21 M4 Competition and love it! In my Corvettes, there was a fuse you could pull to keep the exhaust baffle open at all times. Is there one in the M4? First time BMW owner, really enjoy the forum and information. Lots to learn!

Thanks
On the older F8X, you could simply unplug each of the 2 valve controllers near the exhaust and that would leave the exhaust flap open at all times. Might be similar for the G8X - not sure!
Does the exhaust button not accomplish this? I know in my g20, you had to actually drive in sport/sport+ for the valve to be open, but I figured the exhaust button would solve for any need in doing this.
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      04-25-2021, 09:42 PM   #4
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What he said ^, just press the button
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      04-25-2021, 10:48 PM   #5
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Quote:
Originally Posted by ACremona22 View Post
Does the exhaust button not accomplish this? I know in my g20, you had to actually drive in sport/sport+ for the valve to be open, but I figured the exhaust button would solve for any need in doing this.
I have a g20 and even on sport + the valve opens and closes depending on the rpm. Ended up disconnecting it. Not sure about the g80 or g82 since it actually has a button for it.
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      04-26-2021, 01:53 PM   #6
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The button still closes the valves at a bunch of random times.
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      04-28-2021, 12:58 PM   #7
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That's what I've seen, and on my '18 Vette, pulling the fuse kept them open all of the time, otherwise they would close at certain constant speeds even in Track mode. Youtubes have shown how to disconnect the plug/s. Just have to do it with valves open. Older one used vacuum, not electric to operate the valves. Same idea--pull and plug the hose.
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      04-28-2021, 06:27 PM   #8
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Quote:
Originally Posted by vetteflier View Post
That's what I've seen, and on my '18 Vette, pulling the fuse kept them open all of the time, otherwise they would close at certain constant speeds even in Track mode. Youtubes have shown how to disconnect the plug/s. Just have to do it with valves open. Older one used vacuum, not electric to operate the valves. Same idea--pull and plug the hose.
Is there a plug into exhaust near the end? On the g20, the right exhaust tip/muffler had a plug that electronically controlled the flap. Once unplugged after it was open, it would prevent it from closing.
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      05-01-2021, 10:00 AM   #9
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I unplugged mine the other day and was suspicious that there was some fail safe that closed them after I unplugged.

So I plugged em back in.
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      05-01-2021, 10:32 AM   #10
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Quote:
Originally Posted by LBbluem2 View Post
I unplugged mine the other day and was suspicious that there was some fail safe that closed them after I unplugged.

So I plugged em back in.
So there is a plug? What made you suspicious? If like the G20, there would be no way for it to close without the electronics.
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      05-01-2021, 12:16 PM   #11
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Quote:
Originally Posted by ACremona22 View Post
Quote:
Originally Posted by LBbluem2 View Post
I unplugged mine the other day and was suspicious that there was some fail safe that closed them after I unplugged.

So I plugged em back in.
So there is a plug? What made you suspicious? If like the G20, there would be no way for it to close without the electronics.
It just didn't sound louder, the plugs are super easy to get to and un plug.

Once my cars back from ppf I'll mess with it more.
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      05-02-2021, 01:17 PM   #12
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Unplugged the left connection yesterday. But, the valve stayed only partially open. It seems if the flaps are fully open, you can unplug and they will stay. But tried half a dozen different times to get them fully open and couldn't. Plugged it back in and will ask my tech at the 1200--1000 for me, service if he can keep them open all of the time. Much easier in the Vette, and I would think there would be a fuse that killed the connection, but again, will the default be full open is the question.
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      05-02-2021, 02:27 PM   #13
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Quote:
Originally Posted by vetteflier View Post
Unplugged the left connection yesterday. But, the valve stayed only partially open. It seems if the flaps are fully open, you can unplug and they will stay. But tried half a dozen different times to get them fully open and couldn't. Plugged it back in and will ask my tech at the 1200--1000 for me, service if he can keep them open all of the time. Much easier in the Vette, and I would think there would be a fuse that killed the connection, but again, will the default be full open is the question.
I think I'll need someone in the driver seat giving it some throttle while I pull the plugs
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      05-02-2021, 02:36 PM   #14
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That may work.
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      05-02-2021, 07:26 PM   #15
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Or maybe upon cold startup? Aren't they wide open for that?
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      05-02-2021, 07:31 PM   #16
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Didn't the //M engineering video talk about how this isn't a binary valve any more (off/on) and now it's variable?

Trying to wrap my head around robbing the car of some back pressure when the ECU calls for it by leaving the valve stuck open at this point.
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      05-02-2021, 07:33 PM   #17
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Quote:
Originally Posted by ACremona22 View Post
Or maybe upon cold startup? Aren't they wide open for that?
That's what I tried and it seems like it somehow closed them back up
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      05-02-2021, 11:11 PM   #18
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It's a shame the m440 sounds louder than a m3 or m4.
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      05-03-2021, 06:34 AM   #19
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Like mentioned above, it doesn’t seem to be an on/off. I’ve noticed a few different exhaust notes... standard with nothing enabled, then pressing the exhaust button, then a tad louder once I press the M1 or M2 button. Is this all in my head, or does the exhaust get even louder even after pressing the exhaust button on the center console?
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      05-03-2021, 08:56 AM   #20
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M sound control off is the valve always closed no matter the programming. The engine mode determines how open the valve goes with M sound control on.
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      05-04-2021, 12:05 PM   #21
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It appears to be variable, whatever the ECM is calling for. Interesting about back pressure, as this is a turbocharged car. Vette was never an issue. I don't think it would be a problem, as two pipes are muffled all the time. However, I'm not an expert on back pressure with respect to turbos.
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      05-04-2021, 12:18 PM   #22
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Quote:
Originally Posted by Ghozthunter View Post
It's a shame the m440 sounds louder than a m3 or m4.
LOL... My wife 2021 x3m40i with fused pulled. is louder than my M3 at sport+. at cold start. and on the roll...

some how those B58 motor sounds very good.
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