Oil temp discussion

scotty305 · 03-06-2008, 02:32 AM

The axiom I've heard from some drag-racer types was "you want hot oil and cold coolant." From my limited understanding, the hot oil has less friction due to viscosity, and the cold coolant kept cylinder head temps cooler (which kept the intake charge cooler), plus the coolant transfers heat more efficiently than oil. I think I heard numbers like 140F and below for coolant temps, don't recall hearing anything about oil temps. Then again, I think drag guys are a little nuts sometimes, and that might not work for street cars or road-racing. In addition, we don't have nearly as many oil-bathed moving parts (lifters, cams, rods, bearings, etc...) so I'm not sure friction from oil viscosity is such a concern for the rotary.

I remember reading an article about the rotary-powered American Lemans car (the Sportsbook-sponsored Courage chassis, I think), and they mentioned it was difficult to package the huge oil coolers required for the 3-rotor powerplant. It would be interesting to hear from those guys what sort of oil temps they were looking for. I wonder if oil temps are mentioned in the Racing Beat catalog, there's all kinds of good info in there.

03-06-2008, 02:32 AM	#2
scotty305 Rotary Fan in Training Join Date: Mar 2008 Location: Culver City, CA Posts: 84 Rep Power: 18	The axiom I've heard from some drag-racer types was "you want hot oil and cold coolant." From my limited understanding, the hot oil has less friction due to viscosity, and the cold coolant kept cylinder head temps cooler (which kept the intake charge cooler), plus the coolant transfers heat more efficiently than oil. I think I heard numbers like 140F and below for coolant temps, don't recall hearing anything about oil temps. Then again, I think drag guys are a little nuts sometimes, and that might not work for street cars or road-racing. In addition, we don't have nearly as many oil-bathed moving parts (lifters, cams, rods, bearings, etc...) so I'm not sure friction from oil viscosity is such a concern for the rotary. I remember reading an article about the rotary-powered American Lemans car (the Sportsbook-sponsored Courage chassis, I think), and they mentioned it was difficult to package the huge oil coolers required for the 3-rotor powerplant. It would be interesting to hear from those guys what sort of oil temps they were looking for. I wonder if oil temps are mentioned in the Racing Beat catalog, there's all kinds of good info in there.