On Fri, 10 Feb 2006 09:24:41 -0800, "Al"
wrote:


"Chris Wells" wrote in message
.. .

How are "normal" airplane engines tuned to run at a lower rpm? What
changes would have to be made to an automotive engine to shift the
power band down accordingly?

Lengthen the stroke. High RPM engines have a large bore, and short stroke.
Low RPM engines have a longer stroke, and smaller bore, all else remaining
equal.

Al

Not necessarily so. The myth that high speed engines must be over
square, and low speed engines under square is just that. Piston speed
is what matters, to a large extent, and rod angle - which dictates rod
length.

When you say all else remaining equal, you leave yourself wide open,
because it seldom is.