: The fuel economy improvements are seen at lighter loads. At aircraft type
: loads (60+%) and at altitude you can't run lean and/or stratified so you
: don't gain much economy.

: The improvment in power from the increased volumetric effciency and charge
: cooling would still apply.


The "stone-age" of aviation engines which many people gripe about do not appreciably affect the
steady-state operational efficiency save one: air-cooling and octane requirements. Magnetos, fixed timing,
carbs, etc all work rather well in the fixed operating regime of cruise power. A few percent might be
obtainable with variable timing or direct injection, but a BSFC of 0.42 lb/hp*hr (typical for LyContosaurus)
is pretty good for a spark-ignition gasoline engine. If the same engine were to be liquid-cooled and run 12:1
on the 100LL like the automotive counterparts (or 87 AKI "crapgas" on 8.5:1 like their automotive
counterparts), that's more to the tune of 10% efficiency gain. Point-maintainence and ham-fisted-leaning
aside, the old-school works well for efficiency if properly used... just takes more care and feeding to keep
it there.

-Cory


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* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
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