bypass valve

[Tim Sexton]

Installed correctly,  I will guarantee that the factory valve will hold
more boost than you want to run with your 10V. Mine will hold 2.0bar
absolute.   I don't see the problem with the factory valve.  Audi used
them on the Sport Quattro. They don't fail every week do they?  No.   As
long as they last me through until the next tune up, I'm happy.  If one
can't afford to replace a bypass valve, one probably shouldn't be
running higher than stock levels of boost.
    If nothing else, at least the Bosch valve doesn't look like it came
from the nearest autoparts store's "high performance" section... right
next to the 5"exhaust tips, neon license plate frames, "billet" screw on
pedal covers in lovely shades of anodized pink, green, and purple...the
list goes on...
Just my .02
Tim Sexton

91 V8 5speed
87 5kcstq
94 90cs quattro sport

> -----Original Message-----
> From: Joshua Van Tol [mailto:josh at spiny.com]
> Sent: Thursday, February 08, 2001 6:21 PM
> To: quattro at audifans.com
> Subject: RE: bypass valve
>
>
> >I just noticed that these valves are in the wrong way. I
> wonder if that's
> >why they are failing. High pressure comes in from the side
> of the valve, not
> >the bottom (see SJM on bypass diagram) If the high pressure comes in
> >directly opposite the vaccuum hose (ie botttom of valve)
> it's easy to see
> >why it fails.
> >
> >Hmmmmm... It would appear dahlback has screwed up!
>
> Nope, they're in the right way. The inlet is in line with the vaccuum
> hose connection, and the outlet is at 90 degrees to the other two. If
> they were in wrong, they'd never open.

This may or may not be relevant, but in the case of the A4 1.8t's Bosch
valve (and the Forge valve that some have been replacing the Bosch
with),
that description is most definitely backwards.  The high-pressure, or
inlet,
side is the connection that is 90-degrees to the vacuum and outlet
connections.  Connecting these valves backwards, so that the
high-pressure
is connected opposite the vacuum connection, will cause the valve to
open
and leak boost early.

Dan Masi