(Robert M. Gary) wrote in message . com...
For the engine, the higher the RPM the better. However, 1800 is used
because its a high RPM but doesn't suck as many rocks into the prop as
full RPM. If you run up to full RPM everytime you'll send up replacing
your prop every annual.

-Robert

1800 (or 1700 or even 1600 in other installations) is selected
because that's where cylinder pressures are highest for the static
condition. Lower RPMs give lower pressures because the throttle is
closed too much, and higher revs will give slightly lower pressures
because the volumetric efficiency of the engine is beginning to drop
off (there's too much friction in the intake and exhaust systems). At
highest cylinder pressures weak mags or sparkplugs are most likely to
cut out, which is what we're checking for.

Dan



"Roger Long" wrote in message ...
I can't remember where I "learned" it but I always thought 1800 RPM was the
limit for ground running leaned to clear plugs. I had a really bad one
yesterday with 250 RPM drop. I taxied back to the shop and they said to try
full throttle before pulling the plugs.

It worked but running the engine full power (near sea level) while leaned
for best power and peak EGT with minimum airflow for the minute it took
seems pretty abusive to me. Maybe you can get away with it because the
CHT's have not yet risen to max.

Any thoughts? What were you taught?