intermittent boost problem

[b.benz at charter.net]

Brian,

Pose the problem to IA, they are very helpful.

Bernie


---- "Brian C. Mills" <briancmills at gmail.com> wrote: 
> I have been trying to track down a boost problem on my 200 20v sedan for a
> while now.  I am fairly new to this so please excuse any mistakes I make in
> providing the appropriate details.
> 
> I have 146K on the clock with original turbo, manifold, exhaust.
> 
> Stage III+ Chipped ECU from Intended Acceleration
> Samco Silicone Boost Hoses
> TurboXS Bypass valve
> 
> All of these mods were done by the previous owner.
> 
> I have driven a few other 200 20v (both sedan and avant) with similar
> configurations, so I have a point of comparison when I claim to be having
> issues.
> 
> Symptoms:
> 
> Boost will cut out and surge back.  For example, in 3rd gear WOT, the stock
> boost gauge will briefly hit 1.8 and cut out completely to 1.0 or less and
> then return only to cut out again.
> 
> The frustrating part is sometimes this won't happen, so I have been told by
> "audi mechanics" in the past that I have no problems.
> 
> The check engine light is on.  If the fault codes are read it may list one
> of the following codes:
> 
> Internal ECU Fault
> Engine Speed Sensor
> 
> I also have a stock ECU, when the stock ECU is in no fault codes are read.
> I have been told that the Internal ECU fault is common on modified ECUs and
> should be ignored, should it?
> 
> I have checked for obvious signs of boost leaks and found none.  Eventually
> took it to a tuner and had it "smoked", they confirmed there are no boost
> leaks in the system.  The tuner put the car on a dyno and found:
> 
> "The car made about 193 hp to the wheels and a 210 lb torque to the wheels.
> However, the boost is being electronically cut at about 5300 rpm."
> 
> Their most recent guess is that something is wrong with the wastegate.  I
> have taken a look over the troubleshooting list at
> http://www.sjmautotechnik.com/trouble_shooting/20vboost.html but I am hoping
> someone here will be able to narrow the list down a bit.
> 
> Thanks for your time and sorry for the long post.  Please feel free to post
> suggestions off list if you think this topic has been too well covered in
> the past.
> 
> Brian C. Mills
> _______________________________________________
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