overboosting (1987 5kcstq)

[TM]

Mike- whatever you do, try to drive conservatively and keep the
rpms below 4400- that was the cut-off point when this happened
to my 5ktq.

It sounds to me like you have a classic case of lower wastegate
hose failure. This is not readily apparent on casual inspection.
When it happened to my '86 5ktq, the symptoms were exactly as
you describe, except that my car was unchipped and had no analogue
boost gauge to provide this type of fine detail.

My mechanic inspected the car and said the hose was fine. When I
insisted further that he make sure the lower wastegate hose was fine
and to then check the wastegate diaphragm, he found that there was
a leak in the lower wastegate hose. This was easily remedied with a
new hose and the car was back to normal.

I admit though, that it was great fun to feel so much boost until
I hit the cutoff, which was violent, abrupt and unpleasant.

That would be the first thing to check- you'll probably have to remove
the hose to properly inspect it. Scott J. keeps a stock of diaphragms,
from what I've heard. I'm sure the Bennetts can help you out as well.

It's good you have a Mockry chip- it retains the safeguards from what
I've been told, so you should be safe from destroying your engine, just
keep the throttle inputs light and the rpms low.

With the right size hose and proper mounting clamps, I imagine this
could also be a very quick and easy fix, although I haven't BTDT.

Taka

-----Original Message-----
From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com] On
Behalf Of Motor Sport Visions Photography
Sent: Thursday, November 29, 2001 11:20 PM
To: quattro at audifans.com
Subject: overboosting (1987 5kcstq)


On the way home from the QCUSA driver's school at Sears Point (my car
was just parked there, I was taking pictures) my car developed a massive
overboost problem. Perfectly drivable as long as I keep my foot out of
it, but boost comes on much stronger and at lower RPMs than usual...at
minimal throttle I hit 1.8 bar on the gauge and hit overboost (qlcc
chip, Scott Mockry 1.8 bar spring...like a Charlie spring). I made it
home fine, in fact didn't hit overboost once after realizing what was up
and keeping my foot out of it.

I stopped to take a peak at a gas station, but not much light. No
obvious hose problems at the WG lower chamber so I am guessing it is a
sticking WG (doubtful, this came on all of a sudden), or more likely, a
torn WG diaphragm.

Questions:

1. Am i okay to keep driving the car (as in the 200 mile round trip to
Sears Point tomorrow)? I assume so, if I keep my foot out of it like I
did on the way home. Doesn't qlcc code go full rich above a certain
boost level anyway (thinking lack of WOT switch, there's no way to get
the throttle to that position). I have the version that will control
boost without the help of the spring.

2. Who has WG diaphragms in the US???? (I'll ask the Bennett brothers
tomorrow as well since they're up at Sears Point.)

BTW, an aside...my first attempt at shooting on-track with my new toy,
er tool, an Olympus E-10 digital (which I hope to offer on-site prints
with starting next season). I'll post the gallery url as soon as I have
the shots up...I'm posting this prior to even downloading the memory
cards so we'll see how I did.

TIA!

Mike Veglia
Motor Sport Visions Photography http://www.motorsportvisions.com