Jeff,

 

            Congrats on a successful flight.  

 

            I went back a few posts to have a look at your radiator setup again and it seems to me that you are going to be short on your water cooling requirements when the warm weather returns.  (I’m northwest of Toronto and have property near Kirland Lake so I know winters).

 

            Although the cubic area of your radiator seems sufficient (575cu-in) it’s shape (read thickness) is likely your problem.  Many moons ago I tried to make a 6” thick radiator work but I soon discovered the air flow resistance impossible to overcome.  Air would simply go around the inlet duct rather than through it because of the high air flow resistance of the core.  The P-51 had a very thick radiator but it was made up of 1000s of tubes (kind of like soda straws) and you could actually see through the 12” thick rad.  Your rad appears to be standard automotive tube and fin construction, as was mine.

 

            A tube/fin radiator 20” x 20” by 1” thick is far more efficient than one 10” x 10” x 5” thick for 2 reasons.  Resistance to airflow (which I mentioned) and, by the time air gets to the back row of tubes/fins of the rad, it has already been heated up by the tube/fin rows in front of it.  Simply put, the delta T between water and air gets smaller as you progress from front to back.   

 

If you go through historical posts, this list seems to have found a practical maximum radiator thickness of around 2.5”.  Again assuming a standard tube/fin automotive style rad (including evaporator cores).

 

It is imperative that you measure your oil temps and water temps in the same place as everyone else, otherwise, comparisons go out the window.  Are you measuring water temps from the back of the water pump?  Are you measuring oil temps at the bypass block?

 

Your oil cooler placement is getting lots of air, the core is not too thick and it is 90 degrees to the oncoming airflow.  It’s going to work well.  I hate to suggest it but you may need a different shape radiator to get the water temps down.  Go back though old posts and look at Eds cooling arrangement and radiator dimensions.  It is functional and can be adapted to your cowl.  (You have a nice big cowl to work with so I’m sure you will get this sorted out.)

 

NeilK

 

 

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