Thanks Unka Bob I knew you'd know. It's a Walter engine I heard of Walter
engines but I never heard the term LOM for them. Mary Carlson of Carlson
Aviation has one in their Storch replica called a Cricket. I've seen it in their
plane. See I just learned something. Just like Sister Mary Pontius Pilot used to
say "keep your eyes open and your mouth shut and ya moght learn something" :-)

I wonder why they use such a low compression ratio? Even car engines
running regular usually run 8:1. This one is 6.3:1.
It would reduce the stress on the parts, allowing less expensive
materials than a reliable high compression engine.

Roger Halstead
++++++++++++++++++++++++++++++++++++

My normally aspirated 150 HP Lycoming is 7.0:1
for 80 octane while the 160 HP version is 8.5;1
requiring 100LL.

I suspect the 6.3:1 is to prevent detonation
when the turbo is at max boost at 100% power.
Effective compression with turbo boost likely
exceeds 7.3:1. Higher compression could
require water injection and/or higher octane
fuel to safely remain out of detonation range.

Air cooled engines require a lower compression
ratio than liquid cooled engines to insure detonation
is never achieved under any condition. That's what
I was told, anyway.

Barnyard BOb -- 50 years of flight