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      03-12-2013, 12:49 PM   #1
Simon H
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understanding the exhaust valves opening ?

Hello Fellas,
Just got my M5 this week, and today, i had a quick look at when the exhaust valves are open, and shut etc.I notice they didnt open when stationery, on warm up, with any throttle sport setting, but when i returned, with a hot engine, they were continually open. Do they just open, then stay open, when the car is up to temperature, or am i missing any other settings/openings etc ?, Thankyou, regards, SIMON.
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      03-12-2013, 01:20 PM   #2
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My understanding is that the valves are there to increase backpressure during warm up to speed up catalyst heating.
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      03-12-2013, 07:42 PM   #3
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They are completely for noise control.
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      03-12-2013, 08:47 PM   #4
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Quote:
Originally Posted by ColdList
They are completely for noise control.
+1
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      03-13-2013, 03:51 AM   #5
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I know they are for noise control guys, im just trying to understand ,when they are open and shut. On some vehicles, when you press the sport button, their exhaust valves open etc. On the M5, are they just open all the time, when up to temperature ?, many thanks.
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      03-13-2013, 07:05 AM   #6
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I'm by no means an expert, but I spent some time playing around with the exhaust valves the other day. Based on my visual inspection, the only thing leading to the actuator that controls the valve is the vacuum line. I had read some comments in this and other threads that the valves open when the cats warm up or Sport+ mode is selected on the throttle control. Again, I may be wrong, but I do not think either of these is correct since there is no electronic control of the valves - it appears as if the valves can only be opened by sufficient pressure built up in the vacuum line. From moving them by hand I can tell you it's a fairly stiff spring, so a lot of pressure will be necessary - likely once the engine is above something in the 5,000 to 6,000 RPM range. I looked at a schematic of the exhaust on realOEM.com and there is an in-line electronic value farther up the vacuum tube which may control whether or not the exhaust valve is "active" based on certain settings or other conditions, but I do not think it can actually control the valve itself.
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      03-13-2013, 07:15 AM   #7
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Quote:
Originally Posted by AGS View Post
I'm by no means an expert, but I spent some time playing around with the exhaust valves the other day. Based on my visual inspection, the only thing leading to the actuator that controls the valve is the vacuum line. I had read some comments in this and other threads that the valves open when the cats warm up or Sport+ mode is selected on the throttle control. Again, I may be wrong, but I do not think either of these is correct since there is no electronic control of the valves - it appears as if the valves can only be opened by sufficient pressure built up in the vacuum line. From moving them by hand I can tell you it's a fairly stiff spring, so a lot of pressure will be necessary - likely once the engine is above something in the 5,000 to 6,000 RPM range. I looked at a schematic of the exhaust on realOEM.com and there is an in-line electronic value farther up the vacuum tube which may control whether or not the exhaust valve is "active" based on certain settings or other conditions, but I do not think it can actually control the valve itself.
Thanks AGS.
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      03-13-2013, 08:22 AM   #8
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The valve is part of the BMW Active Exhaust and is purely for noise reduction.
It is operated by a vacuum pump underneath the trunk (a common mod on the E90s is
to disconnect the pump via the electric connector in the trunk to keep the valve open).

The basic system was initially introduced on the E46 platform and the electrical function
of the exhaust flap operation is controlled by the MS 41.1 module.
Where 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.

On the F10 it is now reverse where vacuum applied means the exhaust flap is opening
There is no button/setting which will keep the valve permanent open ,the only option is to
"hard wire" the valve in the open position and seal/plug the vacuum line.
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      03-13-2013, 10:10 AM   #9
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Quote:
Originally Posted by jmh View Post
The valve is part of the BMW Active Exhaust and is purely for noise reduction.
It is operated by a vacuum pump underneath the trunk (a common mod on the E90s is
to disconnect the pump via the electric connector in the trunk to keep the valve open).

The basic system was initially introduced on the E46 platform and the electrical function
of the exhaust flap operation is controlled by the MS 41.1 module.
Where 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.

On the F10 it is now reverse where vacuum applied means the exhaust flap is opening
There is no button/setting which will keep the valve permanent open ,the only option is to
"hard wire" the valve in the open position and seal/plug the vacuum line
.
Thanks for the info! Just one clarification I have to your comments. In your last sentence, if you leave the vacuum line connected to the valve actuator you do not need to plug the line, you can just wire the valve open. I did this last weekend with no impact on perfromance that was reported by members that discsonnected the vacuum line but did not plug them.
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      03-13-2013, 10:15 AM   #10
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Quote:
Originally Posted by AGS View Post
Thanks for the info! Just one clarification I have to your comments. In your last sentence, if you leave the vacuum line connected to the valve actuator you do not need to plug the line, you can just wire the valve open. I did this last weekend with no impact on perfromance that was reported by members that discsonnected the vacuum line but did not plug them.
That's correct
Easy enough just leave the line plugged in as is.
Good advice
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      03-13-2013, 10:38 AM   #11
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Quote:
Originally Posted by jmh View Post
It is operated by a vacuum pump underneath the trunk (a common mod on the E90s is
to disconnect the pump via the electric connector in the trunk to keep the valve open).

Where 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.

On the F10 it is now reverse where vacuum applied means the exhaust flap is opening
Interesting info, thanks. Since BMW seems to be concerned with the drain on the battery from the various systems in the car, and will actually shut down non-essential components if the battery is getting low to allow the car to continue to run, for those of us who will be/are using exhausts without the valve, is there an easy way to remove the vacuum pump entirely? I'd prefer to physically remove it, but I suppose a simple fuse removal would stop the electrical drain? Just thought of another question. If the vacuum needed to open the valve is generated at the pump beneath the trunk, and presumably the pump is activated electrically from a RPM sensor on the engine, why would leaving the vacuum line open affect the running of the engine?

Last edited by Used2be; 03-13-2013 at 10:45 AM.
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      03-13-2013, 10:41 AM   #12
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This is all fantastic information, I want to do this to get a bit more exhaust note from my OEM exhaust, has anyone done this permanently that can provide a DIY and a list of parts/supplies needed? WARNING: I'm not very mechanically inclined... so more details, the better!
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      03-13-2013, 10:43 AM   #13
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I
think you're trying to solve a non-issue
The pump itself won't draw any power if the car is shutoff , as long as the car is running the alternator will provide enough power.
If you're concerned about power usage you better not turn the radio, headlights, seat heater/ventilation etc on either

As a side note pulling the plug/fuse will log a fault and will be reported to the BMW diagnostic system if your car is at the dealer. Which in turn will likely have the side effect of them "fixing" it.
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      03-13-2013, 10:47 AM   #14
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Quote:
Originally Posted by nv6425 View Post
This is all fantastic information, I want to do this to get a bit more exhaust note from my OEM exhaust, has anyone done this permanently that can provide a DIY and a list of parts/supplies needed? WARNING: I'm not very mechanically inclined... so more details, the better!
This thread has a lot of info in it and is also applicable to the F10 platform
http://f10.m5post.com/forums/showthr...=808507&page=2
also thread at
http://f10.m5post.com/forums/showthr...=808507&page=2
has useful info in it
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      03-13-2013, 11:01 AM   #15
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Quote:
Originally Posted by jmh View Post
I think you're trying to solve a non-issue

As a side note pulling the plug/fuse will log a fault and will be reported to the BMW diagnostic system if your car is at the dealer. Which in turn will likely have the side effect of them "fixing" it.
Of course you're correct, but I just like to get non-essential stuff out of the way when I can. And, in a worse case scenario when the alternator isn't working for some reason, it is one less draw to allow the battery to function just that little bit longer. I have been in desperate situations while trying to drive home on just battery power and it's frustrating when you don't quite make it. Would the removal of the pump from the car also log a fault if the fuse is still in place? I imagine it would, but that would hopefully have the BMW service department calling you to OK the pump replacement before they "fixed" it.
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      03-13-2013, 11:57 AM   #16
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Interesting. I've observed the car warming up, valves are closed. After a couple minutes the valves open, and I have assumed that they stay opened.

Are you all saying that at some point when driving the valves close again?
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      03-13-2013, 12:06 PM   #17
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Quote:
Originally Posted by nv6425 View Post
This is all fantastic information, I want to do this to get a bit more exhaust note from my OEM exhaust, has anyone done this permanently that can provide a DIY and a list of parts/supplies needed? WARNING: I'm not very mechanically inclined... so more details, the better!
I just wired the valve open this past weekend. You will need three things:
1. Uncoated aluminum wire (available at most hardware stores)
2. Wire cutters
3. A 1/2 inch square by 1 foot long piece of wood

It's then a fairly easy process to wire open the valves:
1. Maually open the valve with your finger and insert the piece of wood up the outboard tailpipe to hold the valve open.
2. Cut a length of wire about 6 or 7 inches long.
3. Fasten one end of the wire around the joint in the valve control arm.
4. Pass the other end through the hole in the bracket that mounts the valve actuator to the exhaust system and fasten it tightly.
5. Remove the piece of wood from the exhaust pipe and ensure the valve remains open.
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Last edited by AGS; 03-14-2013 at 10:40 AM.
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      03-13-2013, 03:00 PM   #18
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Quote:
Originally Posted by AGS View Post
I just wired the valve open this past weekend. You will need three things:
1. Uncoated aluminum wire (available at most hareware stores)
2. Wire cutters
3. A 1/2 inch square by 1 foot long piece of wood

It's then a fairly easy process to wire open the valves:
1. Maually open the valve with your finger and insert the piece of wood up the outboard tailpipe to hold the valve open.
2. Cut a length of wire about 6 or 7 inches long.
3. Fasten one end of the wire around the joint in the valve control arm.
4. Pass the other end through the hole in the bracket that mounts the valve actuator to the exhaust system and fasten it tightly.
5. Remove the piece of wood from the exhaust pipe and ensure the valve remains open.
Awesome AGS, thanks!
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      03-13-2013, 05:21 PM   #19
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Quote:
Originally Posted by jmh View Post
This thread has a lot of info in it and is also applicable to the F10 platform
http://f10.m5post.com/forums/showthr...=808507&page=2
also thread at
http://f10.m5post.com/forums/showthr...=808507&page=2
has useful info in it
You just HAD to bring up[ that thread didn't you?-lol

Here are a few pics of when I had the OEM exhaust on and the valves wired open with aluminum wire. They are stiff but mechanically it is a very simple process.
Attached Images
  
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      03-14-2013, 08:35 AM   #20
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The next step in this process would be to gut the OEM muffler. Sure thinking about that mod next.
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      03-14-2013, 09:17 AM   #21
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Quote:
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The next step in this process would be to gut the OEM muffler. Sure thinking about that mod next.
I am running a modified OEM muffler setup on my car. You can actually get those from Performing imports. It removes the valves altogether and replaces the OEM 45mm pipe with a 65mm to make it basically a straight thru system. Sounds very nice as well. Nice throaty V8 sound without any raspiness or over the top noise. They are also now in the process of developing prototype tips to enhance the look over the small OEM ones.
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      03-14-2013, 10:13 AM   #22
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Quote:
Originally Posted by ColdList View Post
I am running a modified OEM muffler setup on my car. You can actually get those from Performing imports. It removes the valves altogether and replaces the OEM 45mm pipe with a 65mm to make it basically a straight thru system. Sounds very nice as well. Nice throaty V8 sound without any raspiness or over the top noise. They are also now in the process of developing prototype tips to enhance the look over the small OEM ones.
Thanks for the update, Coldlist. I just responded to you on the ECU tune with regards to Performing Imports. I will definitely contact Ron about the exhaust mod.
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