WOT switch

[Phil@isham-research.demon.co.uk (Phil Payne)]

In message <0716D052C1CFD0119D280060979FBE9A141B8B@a1.matrix.com.pl> Aleksander Mierzwa writes:

> 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"

According to the documentation, the cold start valve is _also_ triggered
if a _really_ cold engine is accelerated hard.  We all know we shouldn't
do this ...

> 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.

In early systems, this valve was also the main acceleration enrichment
mechanism - see below.

> 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
> period.

Some cars don't have frequency valves - the non-emission controlled WRs,
for example.

The interest I have is in performance modifications to electronically
and partly electronically controlled engines.  On an MB/MC-2/1B engine,
for instance, certain assumptions are built into the system.  Changing
things like cam profiles, air filters, turbos, gas-flowed ports and the
like without telling the ECU is likely to cause more problems than it
solves.  Even a different cam needs the ECU to be 'chipped' to exploit
it.

--
 Phil Payne
 phil@isham-research.demon.co.uk
 Phone: +44 385302803  Fax: +44 1536723021