Dan Luke wrote:
The settings I mentioned, and some that are even more over-square, are listed
as permissable in the POH.

Here's what I found in a Lycoming flyer for a higher-power version of the
TIO-540:

"A power setting of 2200 RPM and 31" Hg manifold pressure is recommended for
all cruise flight."


Your quotation refers to a turbocharged engine which by definition would always
be operated oversquare in cruise anyway. I doubt you will ever see 31" of
manifold pressure in a normally aspirated engine. They just can't do it.

That being said, I have been a long time fan of using the lowest RPM I can get
away with for cruise flight mostly because of my experience with bigger twins.
The slower they turn, the quieter they are, and the less tired everybody in
earshot becomes.

I look for whatever combination of low RPM and manifold pressure can give me
65-75% power. I still want the speed but don't need the extra noise trying to
get an extra 7 knots out of the beast. All things in moderation...



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com