Thread: Adjusting 3.9 V8 Hitachi MAF

I currently have poor around town economy in my 92 3.9 range Rover at 20-22 L per 100Ks, while economy onthe highway is good at 14L per100Km.
I have a quite modified engine with Thor manifold, Unichip, modded heads. It has been Dyno tuned 3 times but my impression is that on a dyno they tune for max power with little time or thought given to part throttle operation.
I thought Iwould adjust the MAF so it gives a leaner mixture baseline.
There are two outputs to the ECU from the Hitachi MAF
The variable output (blue/orange band)is within spec ign on at 0.4 volts and it increase to 2+ volts on revs. Goes to ECU terminal 35

There is a pot on the MAF which varies the output of another blue terminal to ECU 25. This terminal is constant at about 0.7 volt and screwing in or out of the adjuster varies this set voltage which remains constant at all revs..
My question is
Do I reduce or increase this voltage to lean the mixture???

I have exhausted my electronic knowledge on this and I have found nothing in the manual or internet.
Is the set voltage a reference against which the variable voltage compares? if so common sense would dictate that an increase would reduce the difference between the two and therefore result in a smaller differential signal for a given airflow and that this effect would be most at idle .
Any help appreciated.
Regards Philip A

I found a reference on the Rpi site.
Higher voltage gives higher CO, ie richer.
So to lean the idle you turn the screw out which reduces the voltage.
So I will try to turn it out a bit, as you soon know is CO is too low as you lose idle quality, just like the mixture screw on a carby.
Regards Philip A