re: Bypass valve orientation?

[Phil Rose <pjrose@servtech.com>]

Frank,
FWIW, nipple forward is the direction on the '91 200q.

But you've stirred my curiosity about this cool "designer" bypass valve
(and other variants). If the valve spring tension is different in various
models, I suppose this must be to account for the varying levels of boost?
If so, would "upgrading" the bypass valve be a useful thing to go along
with ECU chipping? For example, would a chipped '91 200q benefit from using
a stock S4 bypass valve--or some other? For that matter, is the stock S4's
bypass valve significantly different (hose dimensions, etc) from the '91
200's?

Phil Rose


>Date: Wed, 8 Jul 1998 22:05:18 -0600
>From: "Frank Amoroso" <famoroso@sprintmail.com>
>Subject: Bypass valve orientation?
>
>Hello fellow Audi heads,
>
>Question regarding the proper mounting position for a turbo bypass valve on
>the S4. The last time we all tuned my stock bypass valve had a diaphragm
>that looked like Swiss cheese so I replaced it with one out of a sport
>quattro.
>
>I recently had occasion to go by Rev Sport Motors in Colorado Springs and I
>picked up a Group A (or B, not sure) aluminum bypass valve. Anodized blue, a
>very nice piece.
>
>My question relates to how the thing should be mounted, it can go one of two
>ways: with the vacuum line nipple facing the motor or facing the front of
>the car. Which way does it mount? The stock vacuum line seems to be made
>such that the nipple (and accordingly the top of the valve points forward),
>is this correct?
>
>My other question has to do with the spring tension on the new valve. It is
>considerably firmer than even the Sport q valve. Should I be concerned about
>this? The aluminum valve has a larger diaphragm so I guess engine vacuum
>from the one end and boost from the other have more surface area to work on
>so they should still be able to upon the valve during shifts. Does this
>logic sound correct oder do I have an expensive bypass valve that doesn't so
>anything now?
>
>Thanks,
>Frank--

Phil

Phil Rose		Rochester, NY
'89 100
'91 200q		pjrose@servtech.com