Governor Max RPM Changes with Temperature?

I have the McCauley governor on my 0-360 with the Hartzell BA prop. One thing that seems to be consistent with this unit is that I can get 2690-2700 pm on the first takeoff of the day, with the engine and oil temps fairly cool, but on subsequent takeoffs with a fully warmed engine it only gives me about 2650 rpm. That's still plenty to get me off the ground nicely, but of course there are occasions where that extra 50 rpm might make a difference.

Anyone know if this a common situation? If so, what is the cure - adjust the governor to give, say, 2730 or so on the cold takeoff? Getting back in there to adjust the governor stops is no fun, but if that's what it takes, then I'll get in there and give it a try.....

My prop is against the stop for takeoff. The governor doesn't have anything to do with it.

Prop

Birkelbach said:

My prop is against the stop for takeoff. The governor doesn't have anything to do with it.

Click to expand...

Mine isn't. I can adjust the stop on the govener and raise or lower the rpm to 2700.

My experience is the same as Mannan's. The low pitch stop on the prop is one factor in takeoff RPM but not the only one, and the governor adjustment does matter, based on adjustments I have made previously.

Adjustments

Adjustments to the governor high rpm external stop should be made with the engine and oil fully warm.
Sounds like prop governing oil not flowing through the system like it does when things are up to temp causing this rpm spread.
Are you using a muti-vis oil or a straight weight?

Aeroshell 15W-150. I don't think oil viscosity or changes in same due to temp are the issue (and no, we don't need to segue into the multi-vis v. straight weight oil debate.. ).

I received a PM from another member who posits the change is due to a plastic housing on the governor that affects the operation once warm, in these rear-mount applications that don't get cooled as well as front mount apps. He had his refitted with a metal part # that cured the same problem he was having. I plan to follow up on that.....

Temperature does indeed affect the high rpm setting. I have mine set to my satisfaction on my O-360/Hartzell/Woodward governor. In the hot summer I see just about 2650 rpm at max, while in the winter it will hit about 2800 (but I pull the prop lever back 1/2" from the stop for 2700.) That is preferable to my way of thinking to adjusting the high stop every season.