Diverter valve question

[dunegoon]

A friend sent me a box of parts and I agreed to help him put it together. The previous owner used this Bosch diverter valve 0 280 142 102 as a blow off valve. I need to confirm it's installed correctly. After hours on the Internet searching, I'm at a loss. Since the Dellorto carbs were dripping in external fuel and dirt, I'm concerned this valve was in backwards and not functioning correctly. To the left is the intake pipe, a small K&N filter was on the end pointed down in the photo below.

20180420_182533SMALL.jpg

[sideshow]

From what I can gather they work both ways, use the one that leaks less.

[Clonebug]

I have been using that same valve or one exactly like it as long as I've been turboed. That's been over six years.
My boost goes into the side of it and the vented side is what I call the bottom.
So I would say he had it backwards compared to mine.

I followed a Volvo site that used that valve.

Mine is actually from a Saab but Porsche also used that valve on some of their turbo cars among others.
It's held up to lots of boost and many miles......plus it only cost me about $12.00

Here is some info on it.....

http://people.physics.anu.edu.au/~amh11 ... _valve.htm

Just make sure you run a filter on it because it is open during vacuum conditions. They are actually designed to be vented back into the intake before the turbo to keep them quiet and to keep from letting dirty air into the system.
The technical term for them would be a "Bypass Valve".

[dunegoon]

Thanks. And thanks for the nifty link.

[kangaboy]

Just make sure you run a filter on it because it is open during vacuum conditions. They are actually designed to be vented back into the intake before the turbo to keep them quiet and to keep from letting dirty air into the system.

I wasn't aware of this, and I run the same BOV that you do. Better get a filter ordered up. Do all BOVs act this way? I don't recall seeing filters on the end of the more expensive horn looking ones.

[Chip Birks]

Mine can't be filtered, but it is also held closed by a spring when under vacuum.

[Clonebug]

The fancy chrome plated ones are a BOV......The Bosch valve you and I use are technically called a "Bypass valve.
A BOV blows off to atmosphere for the cool Whoosh sound and has a spring strong enough to keep it closed except under very high vacuum conditions like shift and throttle lift.
A Bypass valve has a weaker spring and is open in high vacuum conditions like idle and cruise along with throttle lift during shift....but is meant to vent back into a closed intake to keep the noise down for the granny turbo drivers.

The Bosch Bypass valve is a 1" inlet and outlet and is quite easy to find a little filter for it. I use one that was designed to filter a valve cover.
Look on Summit or your local Flaps might still have them available.