Gene Kearns wrote:
On Thu, 11 Sep 2003 08:19:39 +1000, K Smith
wrote:


The core issue is that they try to deliberately run the engine very
very lean at lower revs to get through the EPA regs, but it's been well
known, understood & documented since before WW2 that this is at best
very risky & in a goodly percentage of instances fatal to the engine.


Not necessarily true..... but Ficht didn't get it down right.... so
it *was* a failure. Millions of flight hours have been flown on the
lean side of the curve. Again, it *is* well documented that it is
possible, but not with the Ficht numbers.....

PS...
Don't quote Lycoming figures. Their engines are no more designed to
run lean of peak than Ficht.... they just happen to know it.


Gene who's engines are designed to run lean at power as Ficht does???

OK I won't "quote" Lycoming but I should be allowed to comment:-)

(i) Yes aero engines can & are regularly run lean but as lean as 40 to
1?? That's the figure given by OMC in the early days of Ficht for their
operation a low revs, in keeping with their normal deceptions they also
claimed an 80% fuel saving!!!

(ii) Yes aero engines can & are regularly run lean but they're very low
specific output engines even the best of them not much more than 40
HP/ltr @ WOT, then they're not usually allowed to be lean if above 60%
of max manifold i.e.say 25HP/ltr. The Fichts also run extremely lean
(much more so than the aero engines) @ 25HP/ltr but
(a) The aero is a very slow turning 4 stroke with a sophisticated lub
system which sprays oil under the pistons & has proper oil temp control
(coolers).
(b) The Fichts have no piston cooling whatsoever & are 2 strokes so
have twice as many heat input events for any given period.

(iii) The aero engines are not allowed to be brought back from lean
operation to normal mixtures quickly, indeed usually they are restricted
to slow incremental richening operations over "minutes", rather than
just being suddenly subjected to a normal "full" mixture. Whereas the
Fichts have no such protection from delivering a full mixture into a
lean overheated chamber. i.e. after a long period in a no wake zone at
the upper end of the lean mode then the user spools up quickly,
delivering a full mixture onto an overheated piston & ......... well 1
in 5 what else is there to say:-)


K