Oil under stress heats up quickly. Higher oil pressure in racing engines is used to move heated oil out of the wedge area quickly, keeping the very soft bearing material from melting. The racer has an external dry sump pump with one pressure section producing (set at) 100 PSI and two scavenge sections removing spent oil and crank case gasses from the engine. The crank shaft spray jets are 180 Weber air correctors. The racer has three 72 fin Setrab oil coolers. Just enough oil cooling for 250HP and shifting at 9,600 RPM.

The stock oil cooler is not enough to cool an aircraft engine. The duty cycle of a car is less than 50%. The duty cycle for an aircraft is close to 100%.  Where 1/3 of the car engine is cooled through the oil, closer to 1/2 of the aircraft engine cooling load will leave through the oil. Using an external oil pressure regulator and running return oil through an additional cooler is perfectly acceptable. Gut an old internal regulator and return oil to the sump through the empty shell.

Lynn E. Hanover 

 

Has anyone ever had a flow transducer in the oil circuit? If so, what was the peak flow?

Does anyone know the cc/rev specs and gearing ratio of the oil pump?

If there was past discussion on this on the list please let me know, but as yet I have not been able to find anything.

Bit of background, Steve Boese's oil cooler experiments from a few years back has helped me much but got me searching more for the effect of oil flow on heat rejection in the entire system.

My temps are much better on the ground now that I've relocated the heat exchangers, but I am reluctant to fly again until I know I can get to a decent altitude before encountering max temps.

I dont think flow of oil through an engine built with tight specs would change appreciably from idle to max rpm, but flow through the OCV will rise sharply.  My engine is a 2004 Renesis with a front cover OCV. I think I could get much better control of the oil temp if I could get higher flow through the cooler. I think its all about controlling the average deltaT. so a tighter engine is going to need much higher deltaT through the cooler as flow will be lower.

There are probably many ways that would give me a solution.

• less oil restriction in engine (should have modified those eccentric oil jets). this may be the best solution but I don't really want to open the engine again just yet.
  
• I could put an external OCV set at lower pressure than front cover OCV inline after heat exchanger, more oil is being cooled.
  
• A bigger heat exchanger would also do the job, but I don't think its the best solution as its just a guess on how big to go.
• What I might do is. plumb in a lower pressure or adjustable OCV and solenoid valve in series on oil "out" port on engine, dump oil into a extra heat exchanger then back to sump. with solenoid off, oil flows as it does now, with it on = extra cooling on demand, basically all that happens is oil that would be returned straight back to sump is diverted to a cooler, engine would just see the slightly lower pressure from the second OCV.
  

My theory is that Oil pressure is nice to know but kind of meaningless. Its possible to have high pressure but flow going to the wrong place (sump), which is not good. Pump is fixed displacement so oil has to go somewhere. Ultimately, Maybe an engine with lower pressure due to less restriction within the rotating parts is probably best as it results in higher flow oil to where its needed.

Any thoughts

Cheers  Andrew