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post #61 of 327 Old 12th November 2008, 05:54 PM
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Danish, I understand your thinking on this subject. But, as I understand it (and, I should emphasize, I don't know for sure), the European model M5s do NOT use the same system we use in the US.

I just hope someone on this board who is a chemist (and, understands how carbon forms and condenses), AND who is an automobile engine guru would help us out in trying to figure out what actually causes this build up to happen.

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post #62 of 327 Old 12th November 2008, 06:17 PM
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I was idly thinking... would maintaining positive pressure to the secondary system- ie running it with some kind of fresh air input 100% of the time- prevent fouling?

I suspect that it is fuel and oil laden air going 'backwards' into these air passages that causes the problem.

This might be a 'solution' and not a 'mask, con, repair, etc'...

A
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post #63 of 327 Old 12th November 2008, 06:31 PM
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I was idly thinking... would maintaining positive pressure to the secondary system- ie running it with some kind of fresh air input 100% of the time- prevent fouling?

I suspect that it is fuel and oil laden air going 'backwards' into these air passages that causes the problem.

This might be a 'solution' and not a 'mask, con, repair, etc'...

A
I think that is a good idea, too, Adam. It seems to me that with the Secondary Air pump ON, the air moves through those small holes near the valves and out through the exhaust system, and the pump pressure doesn't let anyting IN. But, with the pump OFF, it is an invitation for the exhaust to go BACK through those small holes and "maybe" gum things up. Leaving the pump on (and using up some horsepower to drive the pump) may reduce the "pollution."

Just a thought.

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post #64 of 327 Old 12th November 2008, 06:48 PM
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something to look foward to when I pick up an M5!

I bet it was a Lease turn in that some poor guy picked up. The Leasee most likely used the cheapest gas around town, not to mention it probably wasn't even 91 octane!

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Originally Posted by jclyman View Post
Danish, I understand your thinking on this subject. But, as I understand it (and, I should emphasize, I don't know for sure), the European model M5s do NOT use the same system we use in the US.

I just hope someone on this board who is a chemist (and, understands how carbon forms and condenses), AND who is an automobile engine guru would help us out in trying to figure out what actually causes this build up to happen.
Do the euro M5's even have this problem? I would think this was done with the US spec engines to accommodate US emissions regulations and thus only plaguing the US M5's.


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post #65 of 327 Old 12th November 2008, 06:57 PM
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I think that is a good idea, too, Adam. It seems to me that with the Secondary Air pump ON, the air moves through those small holes near the valves and out through the exhaust system, and the pump pressure doesn't let anyting IN. But, with the pump OFF, it is an invitation for the exhaust to go BACK through those small holes and "maybe" gum things up. Leaving the pump on (and using up some horsepower to drive the pump) may reduce the "pollution."

Just a thought.
Unfortunately, the pump would quickly overheat and destroy itself. That particular pump is not of such design or duty cycle that it can run longer than in "spurts"

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post #66 of 327 Old 12th November 2008, 07:08 PM
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Unfortunately, the pump would quickly overheat and destroy itself. That particular pump is not of such design or duty cycle that it can run longer than in "spurts"
Agree. Plus that much air into the exhaust/cats would be a problem.... I was just thinking a positive ventilation- just enough to overcome exhaust leaking into the passages.
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post #67 of 327 Old 12th November 2008, 07:09 PM
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Sorry, I would expect a better air pump with what I was pondering. One that would last.

IIRC, some cars came with airpumps that ran full time, before cats were introduced.

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post #68 of 327 Old 12th November 2008, 07:17 PM
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Sorry, I would expect a better air pump with what I was pondering. One that would last.

IIRC, some cars came with airpumps that ran full time, before cats were introduced.
Perhaps some cat-friendly type solvent (Seafoam?) could be blasted through the passages from the pump back every 20k miles? Something that carbon would be soluble in, etc...

Also, yeah, air injection was popular back in the mid-70's before we had 3-way cats. It was one of the first things to go on my '76 Capri as the pump was a huge parasitic drag on the motor.

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post #69 of 327 Old 12th November 2008, 07:33 PM
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Danish, I understand your thinking on this subject. But, as I understand it (and, I should emphasize, I don't know for sure), the European model M5s do NOT use the same system we use in the US.n.
the euro s62's DO have the exact same system as our cars, same heads, same ports, same eventual clogging. BUT, their dme does not monitor for secondary air flow, they do not have the same level of obd2 as we do.

THat is how the powerchip 'work around' works, they make our dme not monitor it as well. I asked powerchip about this, they compared our dme to a euro dme and that is how their software patch came to be.

Mike

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post #70 of 327 Old 12th November 2008, 07:43 PM
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Perhaps some cat-friendly type solvent (Seafoam?) could be blasted through the passages from the pump back every 20k miles? Something that carbon would be soluble in, etc...

Also, yeah, air injection was popular back in the mid-70's before we had 3-way cats. It was one of the first things to go on my '76 Capri as the pump was a huge parasitic drag on the motor.
I'm not sure carbon is soluble in anything, but like I said, we need a chemistry guy to confirm.

And, I, too, remember the drag on the engine with those early systems.

(And, my Mom had a Carpi as well ... )

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