M2 Stock Exhaust Valve

GregoryK · 06-20-2018, 04:21 PM

Does anyone truly understand this valve?

My understanding is that it makes the car run richer. Therefore there are more pops and burbles when it I is open. That's why the car is loud when it is cold. Best performance with the stock exhaust is with the valve closed.

So why does it open in when traction control is off. Why would BMW want the car to run rich in that situation? Does Sports+ do the same thing?

Peasley · 06-20-2018, 04:33 PM

Unless I'm very much mistaken the valves aren't fully open when TC is off, at least they aren't to my ears. They are only fully open in traction mode.

ORIGIN M. · 06-20-2018, 04:35 PM

Quote:

Originally Posted by Peasley

Unless I'm very much mistaken the valves aren't fully open when TC is off, at least they aren't to my ears. They are only fully open in traction mode.

Love traction mode

My neighbors not so much lol

GregoryK · 06-20-2018, 04:59 PM

Quote:

Originally Posted by Peasley

Unless I'm very much mistaken the valves aren't fully open when TC is off, at least they aren't to my ears. They are only fully open in traction mode.

Are you saying that when traction control is on the valve is open? That makes even less sense to me. So you are saying that it is open in comfort and sport? Those are quieter to my ears.

Either way.....what is the point? The Germans would have that valve for a reason....what is it?

Peasley · 06-20-2018, 05:01 PM

Peasley · 06-20-2018, 05:06 PM

Quote:

Originally Posted by GregoryK

Are you saying that when traction control is on the valve is open? That makes even less sense to me. So you are saying that it is open in comfort and sport? Those are quieter to my ears.

Either way.....what is the point? The Germans would have that valve for a reason....what is it?

There's a chart somewhere that shows the exhaust status in the different modes. I shall try to find it

eeyang92 · 06-20-2018, 05:07 PM

Are we talking about the valve in the back? Cause I'm pretty sure that has zero effect on the amount of burbles "generated", it'll simply muffle it if it is closed.

As an example, I have a valve controller that gives me manual control of the valves. The burbles are decided on which mode I'm in, rather than the valve being open or closed.

AndrewC1989 · 06-20-2018, 05:14 PM

The valve is there to help increase/decrease exhaust volume and regulate back pressure as needed.

GregoryK · 06-20-2018, 05:19 PM

Quote:

Originally Posted by andrewc89

The valve is there to help increase/decrease exhaust volume and regulate back pressure as needed.

Awron manufacture a valve controller state in their info that the car performance is best with the valve closed. So I don't get the volume thing. If you want a louder exhaust you buy the MPE. Back pressure makes sense. That would be why it is reduced on startup…..but why would you want that any other time? Clearly the car is tuned for it to be closed (according to Awron anyway).

AndrewC1989 · 06-20-2018, 06:01 PM

Quote:

Originally Posted by GregoryK

Clearly the car is tuned for it to be closed (according to Awron anyway).

It's not a black and white situation. The car requires less back pressure at times and more at others. It self regulates with the valve.

Also you have to remember that noise plays a big part in putting smiles on people's faces, and yes, even people without the MPE want a little more of it when they hoon in sport plus mode vs when they cruising around in comfort.

The valve is there for both of those reasons.

GregoryK · 06-20-2018, 06:04 PM

Quote:

Originally Posted by andrewc89

It's not a black and white situation. The car requires less back pressure at times and more at others. It self regulates with the valve.

Also you have to remember that noise is a big part in putting smiles on people's faces, and yes, even people without the MPE want a little more noise when they hoon in sport plus mode vs cruising around in comfort.

The valve is there for both of those reasons.

Thanks. Mine definitely had more pops in sport +.

CanadianDriver · 06-20-2018, 06:37 PM

Quote:

Originally Posted by GregoryK

Thanks. Mine definitely had more pops in sport +.

+1

ORIGIN M. · 06-20-2018, 06:40 PM

Quote:

Originally Posted by GregoryK

Quote:

Originally Posted by andrewc89

It's not a black and white situation. The car requires less back pressure at times and more at others. It self regulates with the valve.

Also you have to remember that noise is a big part in putting smiles on people's faces, and yes, even people without the MPE want a little more noise when they hoon in sport plus mode vs cruising around in comfort.

The valve is there for both of those reasons.

Thanks. Mine definitely had more pops in sport +.

Mine backfires in Sport +

Like the other day when I passed a Maserati right as I let off the excelerator.... Bam !

AndrewC1989 · 06-20-2018, 09:20 PM

Quote:

Originally Posted by GregoryK

Thanks. Mine definitely had more pops in sport +.

Quote:

Originally Posted by CanadianDriver

+1

Quote:

Originally Posted by ORIGIN M.

Mine backfires in Sport +

Like the other day when I passed a Maserati right as I let off the excelerator.... Bam !

While having the valve open will definitely make the pops and bangs more pronounced, they are actually a direct result of fueling, based on the driving mode you're in (or the tune you have if your car isn't stock).

If you were to force shut your valve(s) in Sport+/MDM the exhaust would still pop/backfire (although it would sound noticeably more muffled), and if you were to force the valve open in Comfort, you could floor it all day long and any way you like but you still wouldn't be getting any bangs.

ZPrime · 06-20-2018, 10:56 PM

^^ andrewc89 nailed it pretty well.

The valve behavior may well change with drive mode (I don't know if anybody has mapped this out), but it's not the only thing affecting the sound. In fact, it's not very noticeable at all - I have the AWRON, and I've messed around with the valve control to try to figure out what is happening. When sitting near a wall, you can hear the valve open or close. The modes go Auto -> Open -> Closed.

Sitting at idle, after the car has gone through the cat-warmup period, the flap is actually open in all drive modes, including Comfort.

ORIGIN M. · 06-21-2018, 12:29 PM

Quote:

Originally Posted by ZPrime

^^ andrewc89 nailed it pretty well.

The valve behavior may well change with drive mode (I don't know if anybody has mapped this out), but it's not the only thing affecting the sound. In fact, it's not very noticeable at all - I have the AWRON, and I've messed around with the valve control to try to figure out what is happening. When sitting near a wall, you can hear the valve open or close. The modes go Auto -> Open -> Closed.

Sitting at idle, after the car has gone through the cat-warmup period, the flap is actually open in all drive modes, including Comfort.

Interesting

GregoryK · 06-21-2018, 02:44 PM

Found this. Thanks to Mr. M2.

ZPrime · 06-21-2018, 08:11 PM

Quote:

Originally Posted by GregoryK

Found this. Thanks to Mr. M2.

Only thing I can think of is maybe my car wasn't fully out of warm-up mode (I think the flap stays open during the warm-up cycle).

This was using the AWRON flap control, which again cycles from Auto -> Closed -> Open -> back to Auto, or maybe it's Auto -> Open -> Closed, I can't remember... but either way

I sat next to a wall at my office, car was in Auto mode. Press the button to go to next mode (Closed), and I could hear the flap motor actuate to close it.

Press again to go to Open, and I heard the motor again, opening it back up.

If Comfort + idle = flap closed, then going back to Auto should close it again... but no noise to be heard moving from Open -> Auto.

Or it may have been the other way around (I don't remember the switching order off-hand) - if it goes Auto -> Open -> Closed, I heard no noise going from Auto to Open, then I heard noise going from Open to Closed, but then I heard noise again going from Closed back to Auto (implying that Auto had the flap open, not closed...)

Maybe I'll get back there with an inspection mirror and make a video at some point.

jmh600cbr · 06-22-2018, 09:39 AM

Quote:

Originally Posted by GregoryK

Found this. Thanks to Mr. M2.

and how does this compare to MPE?

ZPrime · 06-23-2018, 04:51 AM

Quote:

Originally Posted by jmh600cbr

Quote:

Originally Posted by GregoryK

Found this. Thanks to Mr. M2.

and how does this compare to MPE?

The MPE completely overrides the stock valve modes. You control it yourself with the Bluetooth button thing.

bummie · 06-26-2018, 06:11 PM

Pardon my ignorance but what is MPE? Thanks

GoneIn4Secs · 06-26-2018, 08:33 PM

Mpe is way better and more crackling

06-20-2018, 04:21 PM	#1
GregoryK Captain 504 Rep 780 Posts Drives: M2 '18 Join Date: Aug 2014 Location: Canada iTrader: (0)	M2 Stock Exhaust Valve Does anyone truly understand this valve? My understanding is that it makes the car run richer. Therefore there are more pops and burbles when it I is open. That's why the car is loud when it is cold. Best performance with the stock exhaust is with the valve closed. So why does it open in when traction control is off. Why would BMW want the car to run rich in that situation? Does Sports+ do the same thing? __________________ "I would rather cry in a BMW than smile on a bicycle." Ma Nuo
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06-20-2018, 04:33 PM	#2
Peasley General Moron 247 Rep 158 Posts Drives: M2 LCI MT & E30 Drift Slag Join Date: Apr 2018 Location: UK iTrader: (0)	Unless I'm very much mistaken the valves aren't fully open when TC is off, at least they aren't to my ears. They are only fully open in traction mode.
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06-20-2018, 05:01 PM	#5
Peasley General Moron 247 Rep 158 Posts Drives: M2 LCI MT & E30 Drift Slag Join Date: Apr 2018 Location: UK iTrader: (0)
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06-20-2018, 05:07 PM	#7
eeyang92 Captain 319 Rep 660 Posts Drives: LBB M2 LCI 6MT Join Date: Oct 2017 Location: CA iTrader: (0)	Are we talking about the valve in the back? Cause I'm pretty sure that has zero effect on the amount of burbles "generated", it'll simply muffle it if it is closed. As an example, I have a valve controller that gives me manual control of the valves. The burbles are decided on which mode I'm in, rather than the valve being open or closed.
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06-20-2018, 05:14 PM	#8
AndrewC1989 Brigadier General 10918 Rep 4,550 Posts Drives: 2015 328d xDrive Join Date: Aug 2010 Location: NoVA iTrader: (5) Garage List 2015 328d xDrive [8.90]	The valve is there to help increase/decrease exhaust volume and regulate back pressure as needed. Last edited by AndrewC1989; 06-20-2018 at 05:20 PM..
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06-20-2018, 10:56 PM	#15
ZPrime I INDIC8 612 Rep 1,286 Posts Drives: 2018 LBB M2, 6MT Join Date: Dec 2016 Location: Cleveland, OH iTrader: (0) Garage List 2018 BMW M2 [9.50]	^^ andrewc89 nailed it pretty well. The valve behavior may well change with drive mode (I don't know if anybody has mapped this out), but it's not the only thing affecting the sound. In fact, it's not very noticeable at all - I have the AWRON, and I've messed around with the valve control to try to figure out what is happening. When sitting near a wall, you can hear the valve open or close. The modes go Auto -> Open -> Closed. Sitting at idle, after the car has gone through the cat-warmup period, the flap is actually open in all drive modes, including Comfort. __________________ 2004 Matrix XRS 6MT => 2008 VW R32 DSG => 2012 Audi TTRS 6MT => 2018 BMW ///M2 6MT I'm an IT guy by trade and tech nerd by choice. I like HPDEs, parts of US Hwy 129, NC 28, and the Cherohala Skyway. I'm also a fan of aural pleasure.
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06-21-2018, 02:44 PM	#17
GregoryK Captain 504 Rep 780 Posts Drives: M2 '18 Join Date: Aug 2014 Location: Canada iTrader: (0)	Found this. Thanks to Mr. M2. Attached Images __________________ "I would rather cry in a BMW than smile on a bicycle." Ma Nuo
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06-26-2018, 06:11 PM	#21
bummie Enlisted Member 33 Rep 39 Posts Drives: 2017 M2 LBB Join Date: Dec 2014 Location: Manatee County, Florida iTrader: (0)	Pardon my ignorance but what is MPE? Thanks
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06-26-2018, 08:33 PM	#22
GoneIn4Secs Banned 1287 Rep 1,675 Posts Drives: BSM F87 LCI (DCT) Join Date: Jun 2018 Location: GTA iTrader: (0)	Mpe is way better and more crackling
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