Bill Freeman wrote:

    SNIP

Bill Freeman wrote:
The basic design of piston aircraft engines is near optimum.
Remember, these guys have nearly fully explored the design space.
The construction quality is another issue, and could be improved.
There are some new materials which may provide some gains.
The accessories could be improved, esp starter and alt.  The ignition
system can be improved a bit, but the real world gains are in only
two areas - starting and cruise above about 10-12K ft.  For most
of us, the fixed timing mag is amazingly close to optimum.  I
wish there were big gains to be had out there, but they aren't really
there.  The real world benefits of a super sophisticated electronic
fuel injection system compared to an extremely simple and
"stupid" (even crude) Continental fuel injection is also very small
except for starting.  Once running (admittedly, not at all trivial for a
hot start) full rich gives good cooling for full power, and when
throttled back and manually leaned for a multi-hour fixed
throttle cruise, it is very good - assuming a skilled pilot and
well match nozzles.  These are attainable.

The Porsche failed commercially because, altho fully automated,
it was slightly slower than the Lyc due to inadequate attention to
installation specific cooling drag.  Since the 'off design point'
operation, where electronic fuel injection can excel, is a very
small percentage of the flight, the fuel burn is essentially the
same.  Actual buyers would not pay for an elegant, sophisticated,
automated, simpler, smoother and quieter Mooney that was 5 kts
slower.

Back to Jon Roncz's comment in response to the question of
why today's airplanes are so little improved over 50+ yr old
designs.   He said "Because the Wright brothers used up too
much of the magic".    He meant that the old engineers of the
1st half century got so close to the optimum that it left damned
little for us later generation engineers to fiddle with.  Still
true.   There are some tricks left in the bag, but they are
smaller tricks and need to be applied very carefully to be noticable.
There are no great big tricks left in the bag except possibly
a cheap enough and fuel efficient enough turbine/turboprop.
Williams may make this happen, I certainly hope so.

Bill

Bill, you forgot the rotary. The rotary has the potential to be
more durable. No exhaust valves for one big advantage. Especially
turbo charged and with a much better power to weight ratio in the
turbo charged versions. If we ever get some aluminum end housings
it will have a much better power to weight ratio in the normally
aspirated peripheral port versions as well.

Paul Lamar

No, no, I didn't forget the rotary.  I agree that the complete lack of
a valve train is a big plus for mechanical simplicity, which should
mean realiability.  I just get sick of the "std wisdom" that normal
A/C engines are 'antique junk'.  I was only talking about piston
engines, except for the accy stuff which I'd imagine is pretty true
for the rotary too, altho it runs over a wider RPM band than
a direct drive piston engine, so may need more elegant ignition
and injection.

Bill

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