"Friedrich Ostertag" wrote:

We run (perhaps ran might be more accurate) large
recip aircraft engines at '10% lean from best power' (by manually
leaning them during cruise) for many thousands of hours and they
worked fine in that condition, matter of fact they'll continue to
run fine as much as about 30% lean before they get unstable, they
seem to love lean mixtures!...

Do you by chance know whether these had direct injection (injecting the
fuel into the cylinder instead of the manifold)? To my knowledge there
have been direct injection piston engines among the big radials, but I
haven't found any further information about it so far.

regards,
Friedrich

Well, just a comment about domestic automobiles, I didn't mean to
indicate that I operate them below the manufacturers specified
octane ratings, after all, I believe that the manufacturer knows
his engine best and I'd never try to second guess him, but I have
all kinds of friends and relatives who use hi octane fuel in
their cars even though low octane is recommended. (complete waste
I feel) Another thing that I NEVER do is 'recommend to anyone'
what fuel to use. You're bound to get blamed sometime in your
life because a friend's wife got preggy if you do...

About the direct injection, the Argus (ASW aircraft) used by the
Canadian Armed Forces had Wright R-3350-EA1 engines (3700 BHP)
which had direct fuel injection into the cylinder (not just prior
to the intake valve). The Wright R-3350-89A fitted to the
Fairchild C-119 Packet had 'spinner injection', where the fuel
was injected into the spinner of the supercharger, and the P2V-7
Neptune was set up this way too.

--

-Gord.