fuel questions

[quk@sievers.com (Phil Payne)]

In message <144789@sievers.com> quk@sievers.com (Phil Payne) writes:

> > BTW by changing the screw you are raising and lowering the pivot of the air
> > flow plate, which changes the amount of fuel flowing relative to the amount
> > of air passing the plate.  Then the duty cycle changes to compensate and
> > return the system to the correct mixture.
> 
> But this only aligns the curves at idle.  Once the engine leaves idle, the 
> enrichment curve is dependent on the shape of the air mass sensor cone, what 
> the computer does, and what the control pressure regulator does.  I repeat, on 
> the MB, the latter is separate from the warm-up regulator.

Reading my reply again, I realise that it's not exhaustive.  The combined 
system and control pressure regulator fitted to the MB is vacuum-driven off the 
air mass sensor upper chamber. It's entirely possible that this device is meant 
to increase _system_ pressure while decreasing _control_ pressure under load.   

I'm using the JC Whitney gauge, BTW, not the Bosch one.  I've found the JC 
Whitney version very nice as regards fittings and general robustness, but it is 
quite sensitive to sharp knocks de-calibrating it, especially when it's showing 
a non-zero reading.  The Bosch one has a nice thick cushioned rubber covering.

--
 Phil Payne
 phil@sievers.com
 Committee Member, UK Audi [ur-]quattro Owners Club