For those wanting to see inside the stock re-circulation valve

[b930]

Just resealed mine. Here are some pics for info:

Body with covers removed, here you can see the ports that the piston slides to cover / expose.


Fixed end cover on with new seal. The seal also acts as a stopper for the piston as it get pulled in and out. When it is worn, you may here a clunk as the piston contacts the end cover.


This is the main piston. It is a close tolerance fit into the bore of the body.


This is the ported end cover that allows manifold vacuum / boost into the underside of the piston, with a new seal on.


This is the spring and guide that push the piston to close the ports and rest on the seal on opposite closed end cover. Vacuum has to overcome this to pull the piston back away from the ports.




These are the old old seals - 23 years old...




All back together, note the piston covering the ports. The stock recirc valve is a seriously robust bit of kit with close tolerance components. People often call it a piece of crap, I really like the period engineering that has gone into it. Can't imagine how much a new would cost.

[mark houghton]

Good tutorial. The neat thing about these is that they are available quite often used for cheap (I picked one up for $75 and proceeded to chop it to pieces for a project). Yes, well engineered and the only flaw being the brittle nature of the magnesium casting on the IC mounting pillar (your very last picture) where it's threaded to accept the bolt. Prone to cracking at that point.

[b930]

Indeed, mine are helicoiled like most others. Made by KKK also which I never realized.

[JFairman]

I replaced the 2 rotted and hammered out seals in mine when I first bought the car. Then I learned more and got an aluminum aftermarket C2 type valve and elbow hose upgrade and sold that ridiculously oversized slow reacting heavy overengineered peice of crap for $35.
Also upgraded from a short neck to a long neck intercooler at the same time.

The annoying turbo lag right after a full throttle upshift mostly disappeard because the small C2 valve reacts by opening and closeing so much faster than the old one that in my opinion only looks good in a museum and all of the sudden there was all kinds of room under the intercooler for other things including being able to easily reach under there for the throttle linkage or idle speed adjustment with your hand.

It's the biggest improvement you can make to the 36 year old mechanical 930 CIS design

[willtel]

Here is an old thread on replacing the seals.
Bye Bye Clicking Sound..A Slow'N'Rusty Pictorial - BOV Housing - Pelican Parts Technical BBS

[cellison]

Have to ask a dumb question.. how did you know it was time to reseal it (what was the car doing?)before you tore it down?

[JFairman]

It made that annoying clunk noise as the large heavy aluminum piston slammed shut against the aluminum end cap with no cushion/seal to buffer it during throttle lift when you blipped the throttle in nuetral or let off the throttle fast after flooring it with boost.

The inner diameter edge of the semi soft seal acts as a cushion for the piston when it slams shut instead of it hammering shut against the end cap.
I wanted to see the insides anyway.

[b930]

Was leaking boost. I have tried a later type valve previously on a 930 but never noticed much difference to a proper functioning old school unit, but each to his own.

[b930]

Indeed, I'll stick with the old KKK unit though as I personally think there is not a lot of difference. Also, I have no such problem with lag after shifting as i'm using a variable vane turbo, it recovers faster than anything I have driven, even with the old 'piece of junk' recirc valve, plus I have a nice short neck Andial IC I want to keep.

[Ronnie's.930]

Originally Posted by xxzy

The annoying turbo lag right after a full throttle upshift mostly disappeard because the small C2 valve reacts by opening and closeing so much faster than the old one that in my opinion only looks good in a museum and all of the sudden there was all kinds of room under the intercooler for other things including being able to easily reach under there for the throttle linkage or idle speed adjustment with your hand.

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Interesting way to SPAM . . .

[mark houghton]

Originally Posted by Ronnie's.930

Interesting way to SPAM . . .

Wasn't that Fairman's original comment which is being quoted? Or perhaps Jim is a closet spammer with a garage full of gold to sell

This dude has been reported.....