RE: 91 200q owners - low boost

["Mike Miller" <JoMi@msn.com>]

The saga continues!!!
I spent 6 hours Sunday evening with Ned looking into the low boost problem. I 
swapped in a wastegate from an S6 (they are the same) that Ned had "laying 
around" and we tried it out with Ned at the wheel. First attempt got to 1.4 
boost. Ned next tried loading the engine by applying the brakes and throttle 
at the same time and boost went to 1.7. On subsequent tries boost would go to 
1.7- 1.8. Put my old wastegate back on (while doing so noticed that the hose 
that runs from the intake manifold to the turbo frequency valve was crimped 
where it goes over the bracket at the IM end - uncrimped it. This will 
probably be a tech tip in the next Quattro Quarterly). Tried my wastegate and 
boost jumps to 1.6-1.7. and even 1.8 a couple times, but also remained at 1.3 
-1.4 a few times. Tried to isolate.  Best boost was obtained by putting the 
small hose from the turbo frequency valve on the top of the wastegate. (91 200 
20v does not normally have a hose here - just an empty nipple). Played around 
for a while and it seemed like I was getting boost pressure from the frequency 
valve to the wastegate (which lifts the valve and reduces/holds boost 
pressure) too early. Unfortunately, abut this time, we discovered about 1/8 
inch play in the end of the main shaft in the turbo allowing the vanes to hit 
the housing occasionally so our fun for the evening ended. Well, not quite - 
Ned let me drive his car in the ~400hp configuration. The words do not exist 
to describe this experience. At 4k rpm, you find yourself violently thrown 
towards the back seat and 7k and time to shift is *not* very long in 
arriving!! I definately learned alot about how the turbo and associated 
hardware/software behave/interact on that car.
After that, I removed the wastegate spring so no boost would build up and 
drove my car home at a gentle pace. :(   Today the dealer informs me there are 
no turbos in the US so I am going to have to wait to finally solve this 
problem. And I may still have a bad wastegate.

mike miller
91 200q with blown turbo.

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From: 	owner-quattro@coimbra.ans.net on behalf of Phil Payne
Sent: 	Tuesday, August 20, 1996 2:36 AM
To: 	quattro@coimbra.ans.net
Subject: 	91 200q owners - low boost

In message <9608192319.AA15750@wvit.wvnet.edu> Robert Myers writes:

> The pressure regulator provides an additional safeguard to prevent
> sufficiently high boost pressures as to cause detonation, etc.  A positive
> pressure of about 1.2+ bar above ambient (2.2+ bar as would be registered on
> the in-dash gauge if it could still perform this function accurately [it
> can't - the ECU mods see to that]) help generate a whole bunch of extra
> power.  :-)

We're pointing more and more fingers at the turbo.  Did you check its output 
for metal fragments?

Also, if I'd regularly run boost as high as that, I'd check the intercooler.

--
 Phil Payne
 phil@sievers.com
 Committee Member, UK Audi [ur-]quattro Owners Club