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Lowest cost per mile flown motor- 2 stroke
In theory the lead provides lubrication, but in application it causes
sticking and burned valves from un-even deposits on the sealing surfaces
of the valve and seat. Now if you have rotators on the valves there
might be a different story. With the materials used in valves and valve
seats, even antique aviation engines 8^)... valve seat recession hasn't
turned out to be a problem. Unleaded fuel may extend the TBO for top
overhauls. If it is a concern, run a tank of LL through every 4th or 5th
It's true that the 2 stroke (BSFC .6-.65) will burn "far" more gas
than the 4 stroke (BSFC .4-.5) but av-gas costs "far" more than mo-gas
so this offsets the difference.
I was under the impression that the aircooled 4 strokes needed the
lead for lubrication of valves, etc, so while you might get away with
burning auto gas, how much wear do you want to put on your engine top
end? Sounds like people with 4 strokes running auto gas run some of
both types to keep the top end lubed. For the same capacity tank you
will have shorter max range on the 2 stroke.
The thing I liked about the 2 stroke engines was the high power to
weight ratio and small amount of adaptation required from other
applications (such as Snow Mo). And I realized that your cost per
mile/hour in fuel was less with the 2 stroke.
The difference in reliability is real but could possibly be offset by
a redundant power arrangement which would be really nice to have for
other reasons such as mountain flying or extended flight over water.
Its common practice to use reducnt systems in hi rel systems, so why
not the most complicated and critical componant? So save money?
"Gilan" wrote in message ...
A 2-stroke uses far more fuel than the same HP 4-stroke.
Even if a 4-stroke used more fuel, but it doesn't, the reliability alone
makes the 4-stroke a lot safer engine to use. If you are looking around the
100HP range than there are 4-strokes that run fine on 93 auto gas so the
fuel price difference is minimal.
Have a good day and stay out of the trees!
See ya on Sport Aircraft group
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