Slick Goodlin wrote: ↑Mon Jun 06, 2022 10:29 pm
Funny, I was chatting about the care and feeding of a small Lycoming just a few days ago. I don’t own one, but he does and he flies a good bit. He’s a pretty clever guy and one not afraid to track down the right people to help him better understand how to get the most out of his airplane and engine. Imagine my surprise when he said that he’d heard there’s such a thing as too little RPM immediately after start. The idea being that the very lowest RPM delays oil delivery up to the cam and lifters.
I think it depends on the engine model. The O-300 I used to fly had splash lubrication from the crankshaft journals(in addition to oil pump). Therefore, too low rpm equals not enough splash. In addition, cold oil doesn’t splash as well as warm oil. Therefore, when in the cooler oil temp range( but above the pre-heat range), it was actually more important to get to that higher rpm range(which is still a relatively low overall rpm). Apparently O-300 cylinders are not choked(straight barrels).
One would get their oil pressure and go up to 1200 rpm for warm-up and generator charging. From the info I was able to accumulate through searching around, 1200 slings more oil up into the piston area which is warmer and therefore warms the oil faster.
800 rpm is the minimum for prolonged low power as it allows continuous, sufficient lubrication. Idle rpm on the ground is allowed of course but should not be prolonged(such as more than a minute) because 800 some lubricated parts are not being replenished sufficiently.
