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  #1  
Old 12-17-2004, 05:16 PM
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What does it do? Circulating Air Safety Valve

Thanks to a few suggestions from some fellow forum members at the NE-GTG, I identified a very annoying whistle as coming from the Circulating Air Safety Valve on the front of the turbo unit. (I had previously thought that it was a bad turbo bearing.) While I admittedly haven't opened up the valve yet, I'm geussing the either the diaphram or the spring inside are shot, since blocking off the vaccum line to this valve with a BB eliminated a pronounced whistle at 2,000-2,5000 rpm.

So, what does this thing do (when it works)?
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  #2  
Old 12-17-2004, 08:54 PM
ForcedInduction
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ON 85 Kalifornia models it lets the TrapOx warm up to prevent it from cracking. It lets boost air recirculate back to the turbo intake like a wategate for the intake. It helps spool faster on the highway, but unless you somehow have the original TrapOx, I don't see much reason to have it.
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  #3  
Old 12-17-2004, 10:50 PM
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I have a ARV on an 84 Cali car that certainly never had a trap oxidizer. The ARV allows the turbo to "freewheel" by allowing boost to bleed off back out to the turbo inlet. As I understand it, this happened at part-throttle conditions like highway cruise. I suspect emissions reasons? I disassembled the valve cover and placed a 5/16" nut in the spring well to increase the spring pressure on the valve seat so that it would likely never open again. I also plugged up the vacuum line that controls it. Turbo lag is significantly reduced on the highway when transitioning from cruise to acceleration. Whe you take the valve apart you will find a rubber diaphram with a plastic center piece and a rubber seal on the back that seals the opening on the pressure side (outlet) of the turbo. This is what you want to keep closed and thats the reason I increased the spring pressure. Good luck, RT
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  #4  
Old 01-08-2017, 03:11 PM
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Hey Thomas! I have a 84 Cali 300CD, I too have the ARV but no trap ox. I am wondering how is better, with it working or without to be working. I would like to increase the get up and go since the turbo kicks in like around 2400-2500 and according to me it should kick in earlier. If I block this ARV not to open, can I expect a better turbo get up and go a.k.a kicking in sooner. I have the garret turbo. Maybe if I adjust the wastegate I can make it kick in earlier like it should? any answers are welcomed, i love this forum!
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  #5  
Old 01-08-2017, 03:23 PM
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I've never seen any credible evidence that the ARV does anything performance-wise. Lots of evidence that it's there to help more exhaust gasses get into the intake via the EGR valve, so that's what I believe it to be. It will eventually start to leak and create a whistle/lack of boost. When I disabled my EGR I left the ARV because I didn't know what it was at the time and got horrible mileage. Shimmed the cover so the valve won't open and the mileage has been great ever since. So, I don't like it. YMMV.

Also, next time just make a new thread instead of bumping an old (and not very helpful in the first place) one. Looks like rwthomas1 hasn't even been on this site in over five years...

-Rog
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Old 01-08-2017, 03:31 PM
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My '87 SDL was affected by a bad ARV. The plunger deformed so there was a permanent boost leak. I pressed a freeze plug into the compressor section port then reassembled the ARV for looks and since the port to the compressor inlet is an odd shape to plug.

Sixto
83 300SE
98 E320 wagon
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  #7  
Old 01-08-2017, 03:32 PM
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P.S. There's nothing you can do to make the stock turbo spool faster, it's just the way this specific turbo works. Audi had too big of a turbo on their 5000 model (K26) and it took forever to spool. They switched to a K24, which is more efficient at a lower RPM and it became much more drivable. I don't think Mercedes ever played around with that, but I've always been curious what just a more efficient turbo would be like on these. But everyone who switches turbos goes bigger, so we may never know.

-Rog
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  #8  
Old 01-08-2017, 03:44 PM
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Increase engine displacement!

Hasn't someone done a VNT swap?

Sixto
83 300SD
98 E320 wagon
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  #9  
Old 01-08-2017, 08:54 PM
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Shimmed Closed Cover - ARV

Quote:
Originally Posted by Rogviler View Post
I've never seen any credible evidence that the ARV does anything performance-wise. Lots of evidence that it's there to help more exhaust gasses get into the intake via the EGR valve, so that's what I believe it to be. It will eventually start to leak and create a whistle/lack of boost. When I disabled my EGR I left the ARV because I didn't know what it was at the time and got horrible mileage. Shimmed the cover so the valve won't open and the mileage has been great ever since. So, I don't like it. YMMV.

Also, next time just make a new thread instead of bumping an old (and not very helpful in the first place) one. Looks like rwthomas1 hasn't even been on this site in over five years...

-Rog

What cover are you shimming closed?


Thanks!


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  #10  
Old 01-08-2017, 09:07 PM
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Just the outer cover. You take that off and you'll see how if you stick something between the cover and the insides then it'll keep the valve closed. Seems like I used stacked pennies. Just so you can still screw the cover on tight.

-Rog
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