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      04-01-2015, 04:59 PM   #1
saxodreng
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Diverter valve ??

Hi,

I stumbled accros a picture of a Diverter valve for E92 M3
part no. 11727838029

Can someone explain me what this item does and if it has something to do with the Coldstart exhaust leak sound. ??

I read it has something to do with emmisions, but since it is called something with Exhaust and valve, someone (non-mechanic) could be lead to the thourght that something is lead this way and a valve is surposed to leak something if pressure is to high- right ??

thanks in advance

Happy Easter to all
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      04-01-2015, 07:32 PM   #2
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This emissions control valve is part of the A.I.R. system, one for each cylinder bank (located at the rear). An air pump handles secondary air injection into the exhaust near the exhaust ports to help complete burning of the air/fuel mixture while it is still hot enough to do so (immediately after exiting the combustion chamber). The diverter valves are regulating the volume of air injected. It is not an exhaust blow-off valve-- air is moving into the exhaust path through this device, and this would typically be a one-way valve design which prevents backflow to the air pump. In some applications the diverter valve dumps excess pressure from the electric air pump to the outside, but this is usually muffled by routing it into the airbox/plenum.

It is possible that a diverter valve could fail in such a way to allow an exhaust leak on some vehicles, depending on the design, though I have not seen this occur. More likely the gasket for the valve could be blown out due to the valve being loose, corroded, or improperly mounted, creating a leak at the motor side of the valve (away from the air pump inlet side).

As far as the M3 'cold start' and how it relates to this valve-- when the engine is cold, auxiliary air injection cleans up the extra-rich exhaust and raises the temperature of the exhaust which brings the cats up to temp more rapidly. So one other possible source of noise could be your air pump itself. If you change engine RPM with the throttle during the cold start, does the noise you have change in frequency too? If the noise has a rhythm that is independent of engine speed (doesn't change with throttle position), then it could be the aux air pump creating the noise.

Last edited by Beemdog; 04-01-2015 at 08:50 PM.
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      04-02-2015, 04:25 PM   #3
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Beemdog:
Thank you for your reply - this is something I can use - i will imediately go to the BMW dealer and have this checked and controlled.

the noice i get is exactly the same as the cold start leak noise which I experience when i do moderate accellerating until the noise from the induction is higher. sound is especially clear when driving up against a fence or similar.

BMW denmark says that this is quite normal, but I just think that such an expensive car that sounds like the exhaust is leaking is not designed right, and then again BMW does not make errors this way.
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      04-02-2015, 05:26 PM   #4
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Quote:
Originally Posted by Beemdog View Post
This emissions control valve is part of the A.I.R. system, one for each cylinder bank (located at the rear). An air pump handles secondary air injection into the exhaust near the exhaust ports to help complete burning of the air/fuel mixture while it is still hot enough to do so (immediately after exiting the combustion chamber). The diverter valves are regulating the volume of air injected. It is not an exhaust blow-off valve-- air is moving into the exhaust path through this device, and this would typically be a one-way valve design which prevents backflow to the air pump. In some applications the diverter valve dumps excess pressure from the electric air pump to the outside, but this is usually muffled by routing it into the airbox/plenum.

It is possible that a diverter valve could fail in such a way to allow an exhaust leak on some vehicles, depending on the design, though I have not seen this occur. More likely the gasket for the valve could be blown out due to the valve being loose, corroded, or improperly mounted, creating a leak at the motor side of the valve (away from the air pump inlet side).

As far as the M3 'cold start' and how it relates to this valve-- when the engine is cold, auxiliary air injection cleans up the extra-rich exhaust and raises the temperature of the exhaust which brings the cats up to temp more rapidly. So one other possible source of noise could be your air pump itself. If you change engine RPM with the throttle during the cold start, does the noise you have change in frequency too? If the noise has a rhythm that is independent of engine speed (doesn't change with throttle position), then it could be the aux air pump creating the noise.
you get scooby snack for this write up. woof.
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      04-02-2015, 05:36 PM   #5
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Quote:
Originally Posted by Flying Ace View Post
you get scooby snack for this write up. woof.
Awesome! "Low rep" folks like me need all the help we can get...
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      04-02-2015, 07:32 PM   #6
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Quote:
Originally Posted by Beemdog View Post
Awesome! "Low rep" folks like me need all the help we can get...
why so low? If you straight line out your "post to rep ratio" and compare it to mine, I've got you beat.
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      04-02-2015, 07:46 PM   #7
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Quote:
Originally Posted by Flying Ace View Post
why so low? If you straight line out your "post to rep ratio" and compare it to mine, I've got you beat.
Yep. Some of us just suck. Out loud. And we're not funny either. All of us 'forum failures' can just hang our heads and feel the shame. At least I can still type a line without to meny speling errors sumtimes. But one of these days I'm just gonna go Postal on y'all, hack into the system, and run up my post count to Brigadier General. Boo-ya! That'll teach 'em to diss on the Dog.
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      04-04-2015, 04:13 PM   #8
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if your point works and puts my dealer in a situation where he cannot explain why 3 visits to the "most experienced mechanics" didnt fixed it - you will be my guru - i will personally hack the servers of Bimmerposts, even Google for you and promote you to Minister of Defence of all BMW related forums.



I wonder if anyone can beat that ?
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      05-05-2015, 04:14 PM   #9
saxodreng
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Follow up...

Beemdog, your are hereby promoted. Consider yourself as Master Chief Minister of Defence.... :-)

It was the the emmision valve that leaked - sounded like broken manifold gasket.

Both valves was changed today - and boy - for the first time my M3 sounded like a V8 - awesome sound - and i'm so happy.

Thanks
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      05-05-2015, 04:29 PM   #10
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Here I was just getting used to 'Chief Bottle Washer'.

Saxo, very glad your car is fixed. Next time I'm in Denmark, we'll have a beer.
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      05-06-2015, 04:30 AM   #11
saxodreng
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Beemdog:

You just give me a note - and I will meet you and we can grab a beer.

How often are you in Denmark ?
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