Thanks Ed, any comments on the extreme delta between my water 190F and my oil at 110F?

Jeff

 

 

Making progress, Jeff!  Good work!

 

When I first flew with high oil temps the water temps were elevated as well.  When I solved my oil temp problem, the coolant temps also dropped.  So there is no question there is some “leakage” of heat between the oil and coolant system – not too surprising as both circulate in the block where all that hot metal is.

 

In the winter time, I ,like Mark, see coolant and oil temps at cruise down in the lower 140F range – cooler than I would like.  But, in the summer they are in the 160-170F range (both oil and water)

IF I flew a lot in the cold/hot weather, I would probably put some time of hand operated baffle in the oil duct to divert some of the air flow causing its temp to rise and the coolant would tend to follow it up.

 

I have tried using a thermostat on two occasions and almost fired my engine on the ground.  I am not certain but because I am plugs up, I think I may trap some air around the thermostat stopping it from heating up and opening – even though I drilled some 1/8” dia holes around the lip of the thermostat to get rid of any air.  In any case, I never tried flying with one because the engine got too hot just on the ground.  You engine is installed in the “normal” orientation so should be able to operate with a thermostat.

 

Just remember the engine’s cooling system was originally designed for relative low average power being produced (as in touring down the free way at 2500 rpm) where as we are asking for “more power! Scotty!” from take off to level off.  High power = high heat with low air speed = low air mass flow = High temp problems on take off.

 

If you optimize your engine cooling for cruise, it’s likely you will have a cooling deficit during the take off phase.  If you optimize if for take off then you will likely have more drag at cruise than necessarily.

 

While, I am not advocating it, I have accepted the cooling deficit during take off  in order to have my “high speed” aircraft have minimum cooling drag at higher speeds.  I typically will hit 220F with the coolant and 200F with the oil for the 2-3 minutes it takes me to get up to a comfortable altitude and power back a bit, once the airspeed hits 120 mph IAS then my cooling deficit is overtaken and all it good.

At 8000 ft MSL my max possible power (WOT) and rich air/fuel mixture will push my coolant and oil temps right up between 195 and 200F.  So if I had any less cooling capacity (or any more power), I would face a cooling problem, but as it is I am satisfied that my system is very close to “optimum” at cruise.

 

Sounds to me like you are zeroing in on what needs to be done. 

 

Enjoy your success!!

 

Ed

 

 

 

Mark,

I’m not sure what the cruise temps are as we have been flying short, tight circuits only. I think cruise temperatures need to be determined before doing too much else, though re-installing the thermostat may happen.

What is the relationship between the water and oil temp? I guess you have stock Mazda thermostat 195F?

Most of the rotary world has cheek radiators up front, with the oil cooler going in whatever space is left. My oil cooler is up front on top of the PSRU with inlets/outlets on both ends and the water radiator (19x5.5x5.5) is below/behind the oil pan … two independent systems one working too well the other not well enough … see attached photo.

Jeff

 

 

 

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