Hi Paul,

    In response to your email on mileage, I believe you are suggesting
that the rotary be leaned out at light cruise to improve mileage.  We
now have flash control of the PCM and I have tried leaning the mixture.
As you are aware, the mixture is held in the vicinity of 1.00 lambda
based on a target oxygen map.  I tried leaning this target map and
almost immediately got rough running (3%) and a 1% improvement in
mileage.  Mazda appears to map cruise target oxygen to best BFSC/lean
and any attempt to lean the mix quickly leads to misfire.  One possible
reason is that, while the average mix near the plugs may be richer, that
mixture is erratic and unpredictable.

Jim

Thanks for the feed back Jim. How lean did you go
in terms of mixture ratio and EGT?
We are also running at a constant RPM of 5000 to 5500
which might make a difference say compared to 2000 or
3000 RPM typical of car use. It would indeed affect
the stratification effect.

The EGT is down at 150 degrees F lean of peak.
The engine quits running about 200 degrees F lean of peak.
Do you have your mixture maps (both lean and not leaned)
as a function of RPM you can upload to us for study?

Here is some more background info on this subject from
Advanced Engine Technology by Heinz Heisler.

Paul Lamar ...No rotor no motor.

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