Morris Dovey wrote:
J. Clarke wrote:
B A R R Y wrote:
Robatoy wrote:

Btw, I have been reading a bit on diesel aircraft engines. They
seem
to have quite a following.
They had great promise, but Thielert, the biggest player, who
based
theirs on a Mercedes turbo diesel, went BK. According to a
podcast
I
listened to a few weeks back, Thielert left far more orphans than
I
would have guessed.

Since jet fuel is far more available worldwide than avgas, I
thought
it was going to be big! I think the main reason for the lack of
interest in North America was the easy availability of avgas, and
the
availability of a relatively easy 87 octane auto gas conversion
for
many engines. Lots of guys who did the 87 conversion are now
having
problems finding ethanol-free unleaded...

I suspect that ultimately a multifuel engine would be a more
fruitful
approach, and small multifuel reciprocating engines do exist--the
Army used them on trucks a while back and Evinrude has a multifuel
two-cycle outboard. Don't know how the Army does it but Evinrude
uses direct injection like a diesel but with relatively low
compression (by diesel standards) and a spark plug.

Hmm - In my ignorance, I have to wonder how well a low compression
engine would fare at 8000'/2400m. Would that work?

Diesels typically have compression ratios from 14:1 to 24:1. Few
gasoline engines go higher than 12:1 and most considerably less. The
Continental O-200 has 7:1, the Lycoming O-235 has 8.1:1. Both are
very popular aero engines that work fine at 8,000 feet. The
Rolls-Royce Merlin that powered the Spitfire had 6:1 but it also had a
blower.

(I played with diesel model aircraft engines in the 50's, but they
ran
at fairly high compression.)

All diesels run at high compression--it's the nature of the beast that
they have to.

--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)