Carb adjustment using exhaust temp...

[Ed Carryer]

James,
I did an engine controller for a 2-stroke drone aircraft
engine, about 10 years ago now. (wow I'm getting old ;)
it used exhaust gas temperature (EGT) feedback.
the idea is to lean out the mixture and look for
an inflection in the temperature vs mixture
curve. This occurs roughly when you move through
the stoichiometric mixture.

Having said that though,
I don't think you could do it in a car.
An aircraft (the drone) runs at a constant
power setting for most of the time,
so changes in EGT can pretty well be tied
to the changes you are making in AFR.
In a car, the load is never relly constant,
at least not for very long,
and EGT is even more strongly influenced
by load than it is by AFR at a given load.

I should also note
that manual EGT feedback (i.e. through the driver)
is de rigeur for 2-stroke racing carts,
but again, they spend a lot more time at a
constant power setting (WOT) that you can
expect to achieve on the road.

after all this diatribe,
I just re-read your message,
and can answer your question much more simply:
You can't look for an absolute temp,
just the delta-T between cylinders
to infer mixture balance.

good luck,
ed
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