Capt. Geoffrey Thorpe The Sea Hawk at wow way d0t com wrote:
: 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.

Agreed. All I'm saying is that the for the aircraft application, the
operating regime (cruise) is a very small window of operating conditions. If it can
be optimized within that window, but made simultaneously safe to operate outside of
it, that'd be enough. I haven't thought it through completely, so they may be
mututally exclusive.

: 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.

Isn't it a stronger function of compression ratio and CHT, though? Timing
will help manipulate the time at which the peak pressure occurs, but the detonation
margin has very little to do with timing.

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

Agreed. Points suck. Making them lightning-robust might take some
thought, however...

All of these things (solid-state "points," variable timing intelligently
dependent on RPM and manifold pressure, etc) would be very difficult to accomplish
mechanically to aviation robustness standards. Computers like FADEC would make it
easier to implement, but still quite difficult to certify.

-Cory


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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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