wrote in message
...
: In any case, there are exactly two things "wrong" with aircraft engines.
The
: spark timing is fixed and the mixture control is in the hands of the
pilot.
: And you can't do anything about the first problem until you fix the
second.

The first is a compromise, but generally works really well for aircraft
engines... they *do* run at a constant RPM all the time. The second isn't
that big of
a deal if the pilot is properly trained to use the mixture knob. Trouble
is most
aren't because of the great degree of OWT and misinformation out there on
the subject.

Except that the optimal spark timing is a strong function of the air fuel
ratio. To get the full benifit of leaning, you need to change the spark. You
can't optimize the spark for the mixture if you don't know what the mixture
is.

I would argue that the #1 biggest problem with aircraft engines is that
they
are still air-cooled.

Liquid cooling has it's advantages.

Removing the tremendous thermal stresses of having 450 degree
CHT's make most of the "routine" aircraft engine problems go away. Stuck
valves,
cracked exhaust flanges and cylinder heads, ridiculous octane requirements
(100 for
8.5:1?)

Octane requirement is a stong function of spark timing...
Of course, large, open combustion chambers with lower charge motion tend to
require higher octane too.

due to the heat and low RPM, galled cylinders/pistons due to overheating,
shock-cooling, and cold-starts, etc.

Liquid cooling stabilizes everything, lets more power be made more
efficiently
with greater reliability. It doesn't even have to add too much weight.


Getting rid of points would be an improvement also. Solid state magneto's
are not hard to make.

--
Geoff
the sea hawk at wow way d0t com
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