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<< Lancair Builders' Mail List >>
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...Beg to differ. Agreed, it is (a) desirable; (b) often not so difficult,
but
(c) CERTAINLY NOT insignificant. Example: by redesigning the oiling system
on
our development engine, we were able to gain about 15 HP (cruise) and 17.5
HP
(takeoff). In another development, a redesigned coolant pump provided an
increase of about 4 HP (cruise) with the same (high) coolant flow rate as
before. There are more examples. I don't really think those kind of
increases
are insignificant. 19 HP without any increase in fuel consumption or heat
rejection? I'll take that anytime. (And I know certain Winston Cup engine
guys who would sell their sainted mothers into slavery for a definitive 4 HP
increase.)...
Thanks for your interest.
Jack Kane<<
I beg to differ with your differ..
The friction hp at full load is a small fraction of the output horsepower at
the rpms we are talking about. I would guess that the FMEP at 2700 rpm is
less than 20 psi for most any engine. I don't know what brake horsepower
you are talking about to get your 19 hp reduction in friction horsepower,
but let's assume a conventional engine has a BMEP of maybe 165. Friction
horsepower is then only about 12% of the output. Your 19 horsepower
represents 3.8% of 500, or without more data, maybe a 32% reduction in
friction losses. That's a huge reduction in friction. Now at higher rpms,
that in NASCAR engines, engine friction is a large number and has to be
taken very seriously. Maybe your development engine was really bad to start
with or the horsepower increase came from something else. I'm just saying
that for a conventional reasonably well-developed engine it is hard to get
much of an improvement from friction reduction. Still worthwhile, since it
is "free" horsepower, just hard to get more than a 1% overall gain. For
example, the data I see for low-viscosity (synthetic) oil say that you can
perhaps get a 1% improvement at the 75% power level (.75% at full power or
1.5 hp on my 200 hp Lycoming). That is effectively a 1% reduction in fuel
consumption and a give power level and I use that to justify its use. No
investment except the cost of the oil itself.
Gary Casey
ES project
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