"jan olieslagers" wrote in message
...
Richard schreef:

Not bein' a pilot (I just jump out of them), doesn't lean cause an EGT
rise? Isn't there some risk of overheating a valve or somesuch if you
take it too lean?

Leaning does cause a rise in EGT - up to a certain point, which is the
point we want because it means optimal combustion, thus minimum fuel burn
for the HP. Leaning any further will make the engine very inefficient,
even to the point where it stops.

On a sidenote, many engines (especially the US-type aircooled boxers) rely
on a bit of excess fuel for valve lubrication so we get recommended to
keep them on the rich side of the EGT peak.

With the correct type of injectors (on injector equipped engines) they can
be leaned far past where lean valve lubrication is a problem. Without the
correct induction system, many engines will run too rough to allow leaning
into safe areas of lean operation.
--
Jim in NC