I bought a very expensive Callies (the crank shaft people) oil to water cooler to try on the racer. It worked just great. The first weekend out the oil and water temps were the same. 190. Too high. It turns out that water cools oil better than air. So I cut my new cooler apart and found a conventional oil to air cooler inside a metal box. I eventually used that as an oil to air cooler for the transmission. Never to return to the idea again.

 

First you need to add more than a third more water radiator to deal with the heat load. The added coolant runs and the bigger radiator add way too much weight.

 

And the number one reason for not doing this is that the oil will never be cooler than the water. You cannot cool oil to 160 degrees using 180 degree water. You want oil to be 160 degrees or less and the water not over 180.  The oil pressure is fine at 80 PSI hot. Stock relief valves in rotaries for years were set at 71.9 PSI. Also fine. The bearings are way oversized for their loads. Plan for 10 GPM from a stock pump (a ball park number) and 16 GPM from an aftermarket pump using bigger bearing clearances. Do not use a Fram filter for any application. Use Wicks (from NAPA) 350 pound burst cans, or K&N oil filters with 550 pound burst cans.  I use 3 Setrab oil coolers and two K&N filters in my oiling system. Not a single failure since 1980.

 

Lynn E. Hanover  

 

That is interesting.  Does anyone know what the max oil flow rate (@ 6000 engine RPM) is through the cooler?  I think I recall that we are looking for around 80 psi oil pressure.  Correct?

 

Gordon C. Alling, Jr., PE

President

acumen Engineering/Analysis, Inc.