On Mar 6, 7:31 pm, "BT" wrote:

The thing about "older" POH, like your 1965 C-210.. they were not that
explict.

Dependent on the engine, some say keep RPM higher than MP, some don't.

But moving the controls in the wrong order can put the engine
outside its operational limitations. For instance, if the POH allows
24" and 2200 RPM, that setting isn't within the old "square" rule-of-
thumb but it won't hurt the engine. Now, if you pull the prop back to
2200 with the throttle wide open, you're going to get may 25 or 26" MP
and 2200 RPM, well outside the limits set by the manufacturer. The
risk with large-bore, slow-turning engines is detonation, and the POH
tables are designed with avoiding detonation and the awesome damage it
causes.
So that's why we teach people to avoid high cylinder pressures
by reding MP first, then setting RPM. If increasing power, get the RPM
up first and then increase MP.
It's no different than upshifting or downshifting your car; you
don't just mash the throttle to the floor when you come to a steep
hill; you downshift first and then apply the power, and when you get
to the top of the hill you don't upshift until the car's speed is such
that the engine won't have to drop to some very low RPM when you let
the clutch out and apply the power again.
We older guys can remember a time when cars would "ping" or
"knock" when the engine was driven at a low RPM and too much throttle.
That was detonation and it would break rings and knock holes in
pistons and trash the bearings and sometimes heads and cylinder walls
would crack. It was considered very poor driving technique. Now we
have cars with computers and knock sensors and all sorts of electronic
wizardry that keeps the driver from breaking stuff, but it also dumbs
down young drivers and they can't grasp the RPM/MP thing quite so
easily. And automatic transmissions and ABS brakes have made driving
habits even worse, IMHO.

Dan