Optimal rpm for fuel economy???

[Jorgen Karlsson]

Javad and Huw,

I agree that CIS is a very reliable system, but the fact remains that there
are one sensitive part. The warm up regulator, it is the only problem I have
heard of but that is the first component you need modify when you want to
change the mixture on a full mechanic CIS system. Everything works fine
after the change, but the warm up regulators seem to be more sensitive after
that.

Mine works fine, and has done it for a long time even if I have changed the
mixture up and down quite often. Since I have several spare units I do this
to save some fuel. It didn't seem to make a difference on the full load
fuelling on my car anyway, bottomed out is bottomed out. The only difference
was at medium load the exhaust temperature started climbing to unacceptable
levels at around 100mph cruise with the leaner mixture.

The part about the CIS being a piece of crap was a warning, the warm up
regulator can act up very easily when beeing modified. Most of my experience
with broken warm up regulators are from old Volvo turbos (I hate those cars
but I have helped a few friends), strangely enough the VAG warm up
regulators seem to stay together better after the modification. Yes, there
are a few Volvos with Golf warmup regulators around here now...

Catalytic converters need fuel to operate, not much but it is needed and to
much fuel will kill them after a while.

Anyway, we want to go leaner then lambda=1 to get maximum fuel economy.

A simple opamp circuit can add voltages, one opamp with the capability to
drive to the bottom rail (LM324), one voltage regulator, a small cap for the
regulator, one 10k potentiometer and a few 100Kohm resistors is needed. I
think that the LM324 datasheet have an example of an summing amp in it.

We use the pot and the regulator to produce the voltage we want to add to
the sensors output. Then we connect the sensor to one of the positive input
resistors and our voltage to the other.

The negative input resistor is connected to ground.
If we want to run a richer mixture during closed loop we connect the ouput
from the potentiomter to one of the negative input resistors instead.

Jorgen