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  #1  
Old 01-01-2009, 10:43 PM
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Location: Tinley Park, IL
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Another ARV thread -om603

Hey guys,

Can someone explain the way the ARV works?
I feel like I have been low on boost lately..I had the ARV port plugged (where the vac line goes)..anyway, just as an experiment today, I took the plug off, so the port is now open, and I noticed a somewhat significant increase in power. I am thinking that maybe the valve is not closing all the way, or it was not able to when it was plugged. Tomorrow I might open it up and try to make sure it is sealed shut.
My question is, does the valve's operation depend solely upon vacuum, or does the boost pressure also open / close it? Can I just leave the fitting open?

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k
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Old 01-01-2009, 10:53 PM
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Join Date: Jun 2000
Location: Eastern TN
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The ARV leaks pressurized air from the comprssor outlet to the compressor inlet. I heard it has something to do with getting the trap oxidizer to operating temperature quickly. Whatever.

The ARV consists of a piston with a coil spring pushing it against a post in the compressor outlet. There is a membrane around the piston enclosing a chamber subject to vacuum. When vacuum is introduced to the ARV, the vacuum overcomes the spring retracting the piston which allows pressurized air to leak to the the compressor inlet. I don't know if under operating conditions there is enough air pressure to overcome the spring. If so, drill the ARV for a whistle and you'll have yourself a BOV

Removing the vacuum signal should render the ARV inoperative but I found in my 87 SDL the piston was deformed and not properly sealing the compressor outlet port. To make sure ARV is disabled, I sent a 1/2" plug into the compressor outlet port. The compressor inlet port is a slot (arc from 2 o'clock to 6 o'clock in the photo) which I didn't know how to seal. With the outlet port sealed, it shouldn't matter.

If that seems severe, put a stronger spring behind the piston and/or add shims for more spring pressure.

edit - I forgot to mention, I put the ARV back in place. You'll draw unfiltered air through the ARV cavity if you don't reinstall at least the cover and cap the vacuum port. No need to cap the port if you refit an untorn membrane.



Sixto
87 300D
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  #3  
Old 01-01-2009, 11:06 PM
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Thanks, Sixto, that helps a lot.

So in your picture, is this with just the cap off of the ARV or the housing?
Is there anything behind this flap that I need to look at, too?
It might make more sense once I take it off tomorrow
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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k
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Old 01-01-2009, 11:23 PM
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smoke gets in your eyes
 
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,832
I should have said this is the Garrett setup. I have no idea what a KKK ARV looks like.

That's what you'll see when you remove the ARV. The spring, diaphragm, piston and some plastic cup thing will come off with the ARV. The brass plug won't be there unless someone beat me to it

There is no flap.

Sixto
87 300D

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