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RE: WOT switch

Because Audi is a long-time leader in the "make your car complicated"
contest, there are three devices to richen the mixture on the
turbocharged K-Jetronic injected engines:
1) A cold start valve. It is triggered by the ECU at startup and sprays
additional fuel into intake manifold for several seconds after starting
cold engine. It is only "on" or "off"
2) A warm-up regulator. This is a simple electromechanical device
consisting of bimetallic spring, electric heating element and a valve.
It's purpose is similar to that of the cold start valve - when the
bimetallic spring is cold the valve is open and lowers the fuel control
pressure by returning some fuel back to the tank. After starting the car
the heating element heats the spring and the valve begins to close. 
3) A frequency valve. It is used by the ECU to alter the control
pressure depending on signals from the oxygen sensor, throttle switch
etc. I'm not sure if ECU uses it to richen the mixture during warm-up

Aleksander Mierzwa
Warsaw, Poland
87 Audi 5000CS turbo (mine)
88 Renault Medallion wagon (mom's)
91 mountain bike (just in case both cars broke at the same time :-)

> -----Original Message-----
> From:	thyrsted@olsy.dk [SMTP:thyrsted@olsy.dk]
> Sent:	Monday, December 01, 1997 4:42 PM
> To:	phil@isham-research.demon.co.uk
> Cc:	Quattro List
> Subject:	Re: WOT switch
> Okay, if understand you correctly, this would explain the much better
> cold
> weather performance; the only way i am getting fuel enrichment now is
> when
> its triggered by temperature, not the WOT switch. This would also
> explain
> the smoother torque-build up at revs < 3200.
> Is the temp-controlled fuel enrichment gradually, or on/off as in the
> case
> with the WOT-switch ?
> Kenn Thyrsted
> '87 200tqa
> [...]