On Dec 30 2007, 5:42 pm, M wrote:
On Dec 25, 8:13 pm, "Roger (K8RI)" wrote:



A runup doesn't do squat about removing moisture or acid. It takes a
10 to 15 minute flight of take off and cruise power. I've never seen
moisture after that, but I sure have after even a prolonged ground
run.

10 to 15 minutes at cruise prower is a reasonable claim. To say it
takes at least one hours to heat up the engine enough to boil off
water is OWT (which I often hear about). If one thinks a 30 minute
cruise flight is too short to get rid of the water, does he reduce
power to land? The engine cools off as the plane descends and water
starts to accumulate in the oil according to this theory.

10 to 15 minutes in air that is -15 or -20°C won't warm
the oil enough to get the water out. If the weather is cold enough,
the water may not leave at all. We have that problem here on the
Canadian prairies. I wish we had liquid cooling.
Closing the throttle on a warmed-up engine isn't the
same as a cold engine idling. The pistons and rings are much warmer
and the gaps have closed up some. And a windmilling engine generates
much less cylinder pressure at idle than it does on the ground, so
blowby is less.

Dan