Intercooler blow-out and by-pass valve

Peter Berrevoets pjberr at
Wed Nov 29 22:31:38 EST 2000

> >What was the part number on the bypass valve?

Audi Part Number (From a 1994 S4) -  034-145-710-A
also carries Bosch part number 0-280142108

> > Im wondering
> >if I could plumb
> >in some type of double ended blowoff valve or adjustable
> >pressure regulator.

I don't think the blow-off valve is necessary, I think the list consensus
was that you want to keep the metered air in the system and that the bypass
valve solves the pressure spike at throttle snap-shut. So long as you keep
the fuel pump cut-out active (with the resistor mod) you shouldn't have to
worry about over-boost.

> >Also I under stand about installing a fitting into the
> >inttercooler just
> >before the throttle body hose, but clarify please where are
> >you putting the
> >output?

At the turbo end of the metal pipe running from the fuel metering head (air
filter) to the turbo.
This metal pipe connects to the turbo with a rubber boot. I am intending on
drilling a hole in the metal pipe about an inch from the edge of the rubber
boot and brazing in a section of copper pipe. This would keep the high - low
recirculation to the shortest distance possible (just seems like the right
thing to do - gut instinct no 'real' reason) without touching the rubber
boots on either side of the turbo itself. On the '91 20V the family album
shows the fittings molded into the rubber boot itself.

> >I guess it would be helpful to actuall look at the 200Q
> >plumbing to see how
> >this is done.
> >
> >Anyway, keep me posted, and I'll likewise.
> >
> >Regards,
> >
> >Ben

Will do the same and thanks again!

Peter Berrevoets
1990 200TQ
Toronto, Canada

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