RE: Boost problems in Urq

[QSHIPQ@aol.com]

Scott Bristol writes:
>The car has a problem under heavy boost and acceleration. At approximately
>4600 RPM, the boost pressure drops completely and reverts to a normally
>aspirated condition with very little additional pull. The fuel pump is not
>cutting out nor does it appear the computer is alternating ignition spark.
>Also, the boost pressure only reaches 11 psi and maintains that pressure
>until it cuts out. O.K. I know what you are all thinking--Check for air
>leaks stupid. I HAVE! I think I have spent an entire day looking. I have
>tried pressurizing the system and spraying soapy water everywhere, using
>propane around all hose and manifold gasketts... All the hoses to and from
>the intercooler are new. The intercooler itself has been tested as well.
>My question is this. I am going to a friends shop this weekend to double
>check timing curves, frequency valve operations, and recheck CIS system.
>Does anyone have any suggestions....


Don't throw it away yet, Scott.  You've already done most of the diagnostics.
A couple things I would ck.  The resistance across the coil would be one.  The
ground straps between the coil and the valve cover, and the valve cover and
the front of the crossmember would be the second.  The third, which I believe
to be most likely, is that your turbo injested something, creating some
misaligned cold side blades.  This symptom creates a whole variety of problems
(and problems diagnosing), but most common can be the symptoms you describe
(boost wind up, then vortex from bent blades, making boost profile flat or
reversing).  

Pull the intake air boot off the turbo, and look at the blades (you can use a
flashlight and a mirror on the Urq).  Are the leading edges bent, chipped or
chewed?  While you are there, you might as well ck for radial play.  

BTW, the exhaust impellor has been known to eat pieces parts as well, and can
create similar maladies.  I saw one not too long ago where the intake was
perfect, and the turbine was bent.  The "where" question came to mind on that
one. :)

Good luck, let us know what it turns out to be.

HTH

Scott Justusson