Re: 91 200q owners - low boost

[Robert Myers <rmyers@wvit.wvnet.edu>]

Phil,

Thanks for the diagnostic info.  It won't work on my car, though.  :-)
Well, I guess I could test the WGFV, but it does nothing.  Its outlet is
plugged.

I have a gas pressure small regulator obtained from Paul Timmerman connected
from a "T" installed in the line sending manifold pressure to the ECU.  This
regulator provides assist pressure for the stock WG spring which thus allows
a significant increase in available boost over and above what the ECU will
normally allow.  To accomplish this, it is necessary to sidestep the ECU.  A
resistor network, in Paul's method, or a zener diode/resistor, in the
Superchips mod, both connected across the output of the pressure transducer
and ground potential inside the ECU "fool" the ECU into never realizing that
"excessive boost" is happening.

Does the word "rocket" suggest anything here?

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.  :-)

At 04:30 PM 8/19/96 GMT, you wrote:
>In message <9608191350.AA25035@orion.crd.ge.com> mallick@orion.crd.ge.com
(John Mallick) writes:
>
>> Hmmm...now that I think about it, is the function of the grey hose and
>> the wastegate frequency valve to provide backpressure on the diaphragm
>> to keep the wastegate closed, or is it to provide front pressure to
>> keep the wastegate open?
>
>Both/either, depending on what the computer tells the valve to do.  If you 
>accelerate hard uphill in third gear, you can feel a faint cycling effect on 
>the engine's power.  That is this valve doing its stuff.
>
>> The default position of the wastegate
>> frequency valve is to provide turbo outlet pressure to the hose; when
>> energized it doesn't.
>
>No, but it doesn't matter.  It can be tested in situ.  This is the ur-quattro 
>MB and 20v sequence - I expect it will be the same on this engine:
>
>a) Ignition off.
>
>b) Spare fuse into socket on top of fuel pump relay.
>
>c) Ignition on - do _NOT_ turn the engine with the starter.
> 
>d) After four seconds (German mechanics don't service RHD cars) remove fuse 
>   from fuel pump relay.
> 
>The yellow engine warning light will blink 4433 in the usual groups.  The 
>fuel pump relay will be driven by the computer, and the fuel pump will run.
>
>e) Re-insert the fuse, and remove it after 4 seconds.
>
>The engine light will blink 4441 and the control valve N7 will operate.
>
>f) Remove the fuel pump fuse. (J13?)
> 
>f) Re-insert the spare fuse on top of the fuel pump relay, and remove it after 
>   4 seconds.
> 
>The engine light will blink 4442 and the boost limiter valve (the one you're 
>interested in) will be operated.  The pipe that goes from the top of the valve 
>to the wastegate is supposed be connected in turn to the other pipe from the 
>top of the valve and the pipe that enters the bottom.  Take the first pipe off 
>the wastegate, and remove the other two pipes from the valve body.  With your 
>finger over one spigot at a time, you should feel perfect resistance and no 
>resistance alternately to a blow into the valve from the wastegate pipe.  You 
>should also be able to feel the valve operating.  Unlike the wastegate itself, 
>it _is_ important that this valve doesn't leak. Its function is to allow the 
>computer to fill the space above the wastegate diaphragm with either low 
>pressure air (from the turbo inlet) or high-pressure air (from the inlet 
>manifold).  
>
>(If you do the fuse trick again, the computer will operate the cold start
valve 
>for 10 seconds.)
>
>If you want to repeat this sequence, do it by switching off the ignition, 
>replacing the fuel pump fuse, starting the engine, switching off and then 
>repeating.
>
>
>--
> Phil Payne
> phil@sievers.com
> Committee Member, UK Audi [ur-]quattro Owners Club
>
>
___
   Bob
****************************************************
*  Robert L. Myers         rmyers@wvit.wvnet.edu>  *
*  Rt. 1, Box 57            304-574-2372           *
*  Fayetteville, WV 25840                          *
*  Obligatory quattro and sleddog-L references:    *
*  My 3 huskies enjoy riding in my '89 200TQ       *
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