I guess we’ve had this discussion before but to me it still seems like a grey area.

 

The limit has to do with temperature, time, and limiting component.

 

At typical cruise conditions I have coolant temps of 160-170F and oil temps about 20 degrees higher.  Short term climb out (1000 – 2000’) I see oil getting up 215 -220 and coolant around 200.  If I continue climb, I need to reduce power to keep them at those levels; which means climb rates of 500-700 FPM with OAT of 65F, and maybe a bit less if OAT is higher.  I don’t like being limited to that climb rate when I have power for considerably more; but the real question is: Is that temp level an issue if sustained for 10-15 minutes? And what is it affecting?

 

I expect to make some modification to improve airflow through the cooler, just deciding if it is urgent or if it can wait for another 10 -20 hrs of flying. Anytime I go east from my airport I have to climb from 1400’ to about 7000’ to clear high terrain.

 

Thanks,

 

 Al

The object of controlling oil temperature is that temps above 160 degrees begins to reduce power as rotor face temps begin to limit cylinder filling.

 

Second,

The oil temperatures in the wedge will be very much higher than the temperature being reported on the gage. The bearing area is way over sized for the stress levels involved and at the low RPM in aviation use, the bearings will not fail from stress.

 

However the soft overlay on the bearing face has a low melting point. Oil moving off the bearing carries away the heat from wedge oil. In racing the higher oil pressures used, helps perform this function.

 

Some racers just machine off the overlay and run on the copper. Good bearing material, and a high melting point. Extra clearance allows more oil flow for a given pressure.

 

The rotor face can run as high as 400 degrees, and the oil is removing most of that.  

By the time you get to 230 degrees in the sump you are walking on thin ice, as far as rotor bearings is concerned. You could go higher with less throttle (stress from wedge heat) but in the end I think you need more oil cooling.

 

The race car needs 90 water tops and 190 oil tops. At 100 PSI.

 

Lynn E Hanover