Re: Re : fuel questions

[orin@netcom.com (Orin Eman)]

> The membrane valve controls system pressure, in the absence of a control
> valve in the metering head.  In place of the metering head valve, there's
> a disc on a rod that seems to isolate the right-most port of the three
> from the other two.  I think fuel is free to flow between the middle
> and left port.

Perhaps the built in valve wouldn't work at the pressure they wanted, so thedy
used an external valve to control system pressure.

> > >From the wiring diagram, valve N is a "Taktventil fuer Lambdaregelung" - a
> > frequency valve for lambda control.  Odd - because there is no lambda sensor
> > anywhere on the car, and no catalyser.  It runs on leaded petrol.
> 
> > Yup, Lambda freq valve. When an O2 sensor is present, this valve is used to tweek
> > the fuel mixture(by varying the fuel pressure, not sure which one?) to maintain
> > the stoichiometric ratio 14.7:1. Maybe you recall some posts about people
> > setting the CO using the 3mm allen (Hex) wrench in the hole between the air meter
> > and fuel dist. When the O2 is present, you can connect a DVM up to a test connector
> > , 2 pin near the ign dist, and watch the duty cycle of this freq valve. Here we set it to
> > 42% or close. I run mine at 32% to richen it up under high boost.

Yep, just like the MC in my 5k.
> 
> I don't have any O2 circuits.  The only adjustment provided for is the
> standard CO adjustment.  I don't see any way to change a "duty cycle".
> At what frequency is the valve driven?  Mine seems to buzz at 10Hz to
> 15Hz.

10 to 15Hz would be about right.

On the MC, the frequency (lambda) valve is used for more than just fine
tuning the mixture - as soon as you get on boost or at WOT, the system
goes open loop and ignores the O2 sensor, providing fuel enrichment.
It actually runs at a fixed frequency, it is the duty cycle that matters.
A greater duty cycle enrichens the mixture and I set mine around 40%
at idle.

It sounds to me like your (Phil's) car is using a K-Lambda system that
runs open loop all the time - no O2 sensor, hence I'll bet a 50%
duty cycle at idle.

Orin.