M2CS Exhaust Valve Operation

JD_M2D2 · 12-16-2022, 07:16 PM

Hello,

I've always felt my exhaust valves do not function as expected. In my previous car (Audi RS3) the sound difference between Comfort and Dynamic (aka, Sport) was obvious. In the CS, I don't hear any change in exhaust sound between Efficient and Sport or Sport+ modes, regardless of engine temperature or driving conditions. I've scoured the forums to understand how the exhaust functions and encountered much conflicting information.

Some posts indicate the exhaust valves are open during cold start and close when the engine is warm. Others explain how the exhaust valves only open once the engine is warm and in the higher rev range (3800 +). This simply does not appear to be the case for me.

Since I couldn't see the exhaust valves with the stock exhaust system, I was unable to confirm anything. However, I installed the AA EL midpipes and axle back tonight and was able to visually confirm the exhaust valves are closed during cold start.

Can anyone confirm the expected behavior of the exhaust valves? I'd really appreciate any insight!

TYIA!

Davil · 12-17-2022, 05:18 PM

Unlike in the M2C, they seem to do their own thing. Basic rule is if you press the loud pedal regardless of mode things are louder. If you don’t things are fairly quiet. I quite like this.

aroundelway · 12-17-2022, 05:46 PM

Buy a controller and you can switch it yourself. Milltek makes one. It’s a five minute install. First thing I did.

You can also control them with apps like BimmerCode but it only lasts for fifteen minutes.

JD_M2D2 · 12-17-2022, 06:41 PM

Thanks! I will look into a controller next. I did confirm the valves are open at idle, in sport + with engine warm. I was glad to see that

medphysdave · 12-17-2022, 08:04 PM

The stock logic makes the cabin a very pleasant place to be. Valves open is horrific on the highway. The manual control is nice because you can be obnoxious while poking around town. The stock logic makes this difficult to non existent.

NYNick · 12-18-2022, 07:15 AM

Quote:

Originally Posted by medphysdave

The stock logic makes the cabin a very pleasant place to be. Valves open is horrific on the highway. The manual control is nice because you can be obnoxious while poking around town.

Why would you want to be? I never understood the "loud is cool" thing.
It isn't. It's just loud.

medphysdave · 12-18-2022, 07:24 AM

Quote:

Originally Posted by NYNick

Why would you want to be? I never understood the "loud is cool" thing.
It isn't. It's just loud.

Depends on your personality. Sometimes I'm just feeling a bit rowdy. Drive a bit more peppy. The extra noise feeds into the pleasure. It's not for everyone else it's for me.

AlpsRider · 12-18-2022, 02:05 PM

BM3 flash tune will allow you to have the exhaust valves always open according to sport mode. In efficient mode it is as quiet as a church mouse.

JD_M2D2 · 12-18-2022, 02:06 PM

As I understand it, a flash tune would void my factory warranty, correct? If so, that is not an option for me. Either way, I'm not too worried about it... just glad to see the valves do in fact open up at some point.

AlpsRider · 12-18-2022, 04:58 PM

Yes, a flash tune would technically void the warranty and you'd have to swap out the ECU for an older one. If I had a CS I'd probably pass on a flash as well.

aroundelway · 12-18-2022, 05:59 PM

https://www.cgprecision.com/#!/VSC-2...egory=19266005

This is what I run. Not an advertisement but it works well.

I prefer the noise with the valves open it’s not too loud most of the time. BMW is a bit behind other makes with the exhaust control. My AMG wagon is night and day with the flick of a switch in terms of exhaust level, pops and bangs etc.

medphysdave · 12-18-2022, 07:12 PM

Quote:

Originally Posted by aroundelway

https://www.cgprecision.com/#!/VSC-2...egory=19266005

This is what I run. Not an advertisement but it works well.

I prefer the noise with the valves open it’s not too loud most of the time. BMW is a bit behind other makes with the exhaust control. My AMG wagon is night and day with the flick of a switch in terms of exhaust level, pops and bangs etc.

Jealous you have an amg wagon.

Piets94 · 12-20-2022, 03:53 AM

The car is loud on start-up because the turbo wastegates are open. Once the start-up sequence is over the noise quietens down.

When the engine is switched off, the exhaust valves default to open. You can unplug the valves whilst the car is off (and tape up the connectors to protect them) to keep the valves open at all times. I like the sound. I can still hear differences between the engine modes, and it doesn't drone.

M3R1 · 12-20-2022, 11:57 AM

Quote:

Originally Posted by aroundelway

https://www.cgprecision.com/#!/VSC-2...egory=19266005

This is what I run. Not an advertisement but it works well.

I prefer the noise with the valves open it’s not too loud most of the time. BMW is a bit behind other makes with the exhaust control. My AMG wagon is night and day with the flick of a switch in terms of exhaust level, pops and bangs etc.

I have this waiting to be installed.

JD_M2D2 · 12-20-2022, 12:12 PM

Quote:

Originally Posted by Piets94

The car is loud on start-up because the turbo wastegates are open. Once the start-up sequence is over the noise quietens down.

When the engine is switched off, the exhaust valves default to open. You can unplug the valves whilst the car is off (and tape up the connectors to protect them) to keep the valves open at all times. I like the sound. I can still hear differences between the engine modes, and it doesn't drone.

Do you know if unplugging the valve actuators throws a soft code? On my previous car, an Audi RS3, when the valve actuators were unplugged, a soft code was thrown, which decreased power in the upper RPM range. I verified this on my car after swapping the exhaust system and forgetting to plug in the actuators. The dyno numbers were much lower than pre-exhaust install numbers and we couldn't figure out why. Once we plugged the actuators in and did another dyno pull, numbers were back to normal.

Piets94 · 12-20-2022, 12:49 PM

Interesting.

Yes, it does show a soft code on my code reader. Butt dyno would say no power reduction and my times on track have gotten quicker since unplugging the actuators, but too many variables to say for sure.

I wouldn't put it past Audi to do something like that.

PS.08 · 12-20-2022, 02:21 PM

JD_M2D2 I highly recommend the VSC-2 controller; found its really the only solution to have complete control over your valves. Here's a quick video:

https://www.youtube.com/shorts/rkM4_91y-CY

ashmostro · 12-29-2022, 12:35 AM

FWIW I had a CG precision laying around from my prior M5 and put it on my CS, and removed it within a day. The stock actuator tuning is designed to close during low-RPM high-load scenarios which happen a lot in street driving, and with the valves open will result in drone. This is amplified if you have any kind of aftermarket exhaust modifications.

So, my advice is give it a try but with awareness that it may not be your cup of tea depending on your driving habits and preferences.

aroundelway · 12-29-2022, 08:04 PM

I have not noticed any drone with the valves always open. Granted I rarely drive the car so maybe I just have not noticed.

medphysdave · 12-29-2022, 08:07 PM

Quote:

Originally Posted by aroundelway

I have not noticed any drone with the valves always open. Granted I rarely drive the car so maybe I just have not noticed.

really? I think the drone is horrific with valves open at some rpms. Especially highway cruising. I think it's between 2800 and 3000 on my exhaust. I can easily tolerate around town because the rpms are varying a lot.

ashmostro · 12-29-2022, 08:26 PM

Quote:

Originally Posted by medphysdave

really? I think the drone is horrific with valves open at some rpms. Especially highway cruising. I think it's between 2800 and 3000 on my exhaust. I can easily tolerate around town because the roma are varying a lot.

Same as my experience

wolf2871 · 02-08-2023, 05:49 PM

I just got a VSC for my CS and it's acting weird. After about 5 minutes the valves close again and pressing the button for the VSC doesn't do anything.

Faulty VSC? Does the VSC need to be on the driver side vs passenger side? Trying to trouble shoot before I reach out to CG.

12-16-2022, 07:16 PM	#1
JD_M2D2 In the garage 390 Rep 211 Posts Drives: BMW M2CS Join Date: Aug 2013 Location: Boulder, CO iTrader: (1)	M2CS Exhaust Valve Operation Hello, I've always felt my exhaust valves do not function as expected. In my previous car (Audi RS3) the sound difference between Comfort and Dynamic (aka, Sport) was obvious. In the CS, I don't hear any change in exhaust sound between Efficient and Sport or Sport+ modes, regardless of engine temperature or driving conditions. I've scoured the forums to understand how the exhaust functions and encountered much conflicting information. Some posts indicate the exhaust valves are open during cold start and close when the engine is warm. Others explain how the exhaust valves only open once the engine is warm and in the higher rev range (3800 +). This simply does not appear to be the case for me. Since I couldn't see the exhaust valves with the stock exhaust system, I was unable to confirm anything. However, I installed the AA EL midpipes and axle back tonight and was able to visually confirm the exhaust valves are closed during cold start. Can anyone confirm the expected behavior of the exhaust valves? I'd really appreciate any insight! TYIA!
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12-17-2022, 05:18 PM	#2
Davil Brigadier General 6538 Rep 3,073 Posts Drives: M2 CS, 18 Vantage AMR, 00 WRX Join Date: Jul 2018 Location: Australia iTrader: (0) Garage List 2018 Aston Martin V ... [8.33] 2021 BMW M2 CS F87 [9.87] 2000 Subaru WRX GC8 [7.75]	Unlike in the M2C, they seem to do their own thing. Basic rule is if you press the loud pedal regardless of mode things are louder. If you don’t things are fairly quiet. I quite like this.
	Appreciate 1 JD_M2D2390.00 Quote

12-17-2022, 05:46 PM	#3
aroundelway Private First Class 132 Rep 111 Posts Drives: M2 CS Join Date: Jun 2022 Location: USA iTrader: (0)	Buy a controller and you can switch it yourself. Milltek makes one. It’s a five minute install. First thing I did. You can also control them with apps like BimmerCode but it only lasts for fifteen minutes.
	Appreciate 1 JD_M2D2390.00 Quote

12-17-2022, 06:41 PM	#4
JD_M2D2 In the garage 390 Rep 211 Posts Drives: BMW M2CS Join Date: Aug 2013 Location: Boulder, CO iTrader: (1)	Thanks! I will look into a controller next. I did confirm the valves are open at idle, in sport + with engine warm. I was glad to see that __________________ BMW M2CS 6MT IG/TikTok: jd_m2d2
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12-17-2022, 08:04 PM	#5
medphysdave Brigadier General 4583 Rep 4,685 Posts Drives: M2 CS \| 85 of 592 Join Date: Apr 2015 Location: Charlotte, NC iTrader: (3)	The stock logic makes the cabin a very pleasant place to be. Valves open is horrific on the highway. The manual control is nice because you can be obnoxious while poking around town. The stock logic makes this difficult to non existent.
	Appreciate 0 Quote

12-18-2022, 02:05 PM	#8
AlpsRider Brigadier General 2865 Rep 3,843 Posts Drives: M2 Competition, LBB, 6MT Join Date: May 2015 Location: Earth iTrader: (0)	BM3 flash tune will allow you to have the exhaust valves always open according to sport mode. In efficient mode it is as quiet as a church mouse.
	Appreciate 0 Quote

12-18-2022, 02:06 PM	#9
JD_M2D2 In the garage 390 Rep 211 Posts Drives: BMW M2CS Join Date: Aug 2013 Location: Boulder, CO iTrader: (1)	As I understand it, a flash tune would void my factory warranty, correct? If so, that is not an option for me. Either way, I'm not too worried about it... just glad to see the valves do in fact open up at some point.
	Appreciate 0 Quote

12-18-2022, 04:58 PM	#10
AlpsRider Brigadier General 2865 Rep 3,843 Posts Drives: M2 Competition, LBB, 6MT Join Date: May 2015 Location: Earth iTrader: (0)	Yes, a flash tune would technically void the warranty and you'd have to swap out the ECU for an older one. If I had a CS I'd probably pass on a flash as well.
	Appreciate 1 JD_M2D2390.00 Quote

12-18-2022, 05:59 PM	#11
aroundelway Private First Class 132 Rep 111 Posts Drives: M2 CS Join Date: Jun 2022 Location: USA iTrader: (0)	https://www.cgprecision.com/#!/VSC-2...egory=19266005 This is what I run. Not an advertisement but it works well. I prefer the noise with the valves open it’s not too loud most of the time. BMW is a bit behind other makes with the exhaust control. My AMG wagon is night and day with the flick of a switch in terms of exhaust level, pops and bangs etc.
	Appreciate 1 M3R12173.00 Quote

12-20-2022, 03:53 AM	#13
Piets94 Lieutenant 679 Rep 547 Posts Drives: 94 M3, AW 1M, M2 CS Join Date: Jun 2013 Location: Australia iTrader: (0)	The car is loud on start-up because the turbo wastegates are open. Once the start-up sequence is over the noise quietens down. When the engine is switched off, the exhaust valves default to open. You can unplug the valves whilst the car is off (and tape up the connectors to protect them) to keep the valves open at all times. I like the sound. I can still hear differences between the engine modes, and it doesn't drone.
	Appreciate 1 JD_M2D2390.00 Quote

12-20-2022, 12:49 PM	#16
Piets94 Lieutenant 679 Rep 547 Posts Drives: 94 M3, AW 1M, M2 CS Join Date: Jun 2013 Location: Australia iTrader: (0)	Interesting. Yes, it does show a soft code on my code reader. Butt dyno would say no power reduction and my times on track have gotten quicker since unplugging the actuators, but too many variables to say for sure. I wouldn't put it past Audi to do something like that.
	Appreciate 0 Quote

12-20-2022, 02:21 PM	#17
PS.08 Private 363 Rep 72 Posts Drives: 2020 M2CS Join Date: Oct 2018 Location: OH iTrader: (0) Garage List 2020 BMW M2CS [0.00]	JD_M2D2 I highly recommend the VSC-2 controller; found its really the only solution to have complete control over your valves. Here's a quick video: https://www.youtube.com/shorts/rkM4_91y-CY
	Appreciate 1 JD_M2D2390.00 Quote

12-29-2022, 12:35 AM	#18
ashmostro Brigadier General 1254 Rep 4,088 Posts Drives: 2020 M4cs \| 2022 M550i Join Date: Jan 2013 Location: Falls Church, VA iTrader: (27)	FWIW I had a CG precision laying around from my prior M5 and put it on my CS, and removed it within a day. The stock actuator tuning is designed to close during low-RPM high-load scenarios which happen a lot in street driving, and with the valves open will result in drone. This is amplified if you have any kind of aftermarket exhaust modifications. So, my advice is give it a try but with awareness that it may not be your cup of tea depending on your driving habits and preferences.
	Appreciate 0 Quote

12-29-2022, 08:04 PM	#19
aroundelway Private First Class 132 Rep 111 Posts Drives: M2 CS Join Date: Jun 2022 Location: USA iTrader: (0)	I have not noticed any drone with the valves always open. Granted I rarely drive the car so maybe I just have not noticed.
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02-08-2023, 05:49 PM	#22
wolf2871 New Member 15 Rep 17 Posts Drives: M2 CS (On Order) Join Date: Aug 2020 Location: Germany iTrader: (0)	I just got a VSC for my CS and it's acting weird. After about 5 minutes the valves close again and pressing the button for the VSC doesn't do anything. Faulty VSC? Does the VSC need to be on the driver side vs passenger side? Trying to trouble shoot before I reach out to CG.
	Appreciate 0 Quote