Re: rotor for 20v turbo engine

[Sargent Schutt <sargent@novagate.com>]

No, I'm not hitting overboost cutoff. BTDT, so I _know_ what that feels like.
THis is more like a miss, or a very brief cutout of maybe a couple of
cylinders. Crossfire would seem to effect a similar behavior. It is not the
ECU-induced overboost protection, by any means. Furthermore, the car does only
needs to be at 2/3 -3/4 boost (~1.4-1.5 bar) to exhibit this hard
stumble/stutter.  Boost cutout wouldn't be the issue there. Also, if I hit
overboost, I have to cycle the ignition to get the car to go again, otherwise,
after hitting overboost protection, the computer will continuously cut the
motor out at ~2/3 boost. Ergo, this is not an intentional ECU signal. 

It is also erratic with respect to the frequency and operating conditions.
Heat seems to worsen things, though. However, the 'hard stumble' problem will
exhibit itself even when the motor and air temp are both cool (but the engine
warmed up). I cannot reproduce it at will, though. So it's tough to track
down. That said, I haven't been able to pull codes after it does it. When I've
tried to intentionally elicit the symptom, the car runs fine, Murphy's Law, no
codes. 

When it happens,  it's more than a miss, it's not a lean/retarded condition,
it's an abrupt interuption in power, and it takes all of 3/4 second to come
and go. Feels like the motor trips up, and you can feel a 'clunk' type
stumble. The 'wrong rotor' theory makes more sense than anything else. 

What else would cause such a symptom?

TIA for more thoughts everyone. 

Sarge

PS: It seems I'm not the only one who has had/does have these problems, and it
is not 'chip-brand dependant'... no solutions yet, though.


Christopher Hanlon wrote:
> 
> Hmmm.  Again I'll offer a couple of cents, and again I'll admit I have
> little
> experience with audi engines.
> 
> Reduced timing will (should) not cause your car to misfire.  The most
> noticeable
> affect of reduced timing is lack of power.
> 
> Your symptoms sound similiar to what my '89 944 turbo was experiencing.
> My
> car's overboost detection system was coming on.  The system shuts off
> all fuel
> to the injectors, until the boost dropped.  What resulted was a violent
> moment
> when the occupants were flung forward from the sudden loss of power.
> 
> I don't know what fuel injection/boost control the 200tq uses.  The 951
> (944 t)
> uses Bosch Motronic, DME/KLR.
> 
> Could there be a problem with the TAP chip?  Did you see if you
> experienced the
> problem without the added boost?
> 
> Just some thoughts.
> chris
>