Chuck_Harbert@arkwright.com wrote:

Guys, I ended up talking to Steve Presley (tech engr) at Evans who knew the
rotary situation. He confirmed that Mazda water pump is very good for high rpm
and NPG can be used successfully, but you've got to design the system to work
properly from the start. The pumping pressure thru the rads (and thermostat)
needs to be less than 8-10 psi (you don't run a high pressure cap for NPG).
However, the big item is that NPG gets very viscous at below freezing temps and
therefore should not be used where air temps are below 10-15 degF. What happens
is that the NPG won't move thru the rad and the engine overheats. I told him
that it was in an airplane and he recommended not to use it unless you stayed at
low altitude, or somehow made sure that the rad didn't get the NPG below
freezing in some portion. With that info, since I intend to fly at high (>10K')
altitude, I'm switching to 50-50 EGW. He did say they were working on some
viscousity additive to solve this problem, but it's months away.

We also talked about pump speed and the limiting factor of cavitation (fluid
vaporization(boiling)), and that you may have to slow the pump down (as the
Grand National guys do) in order to keep the system operatiing properly. High
pressure caps help at higher altitudes.

I am relieved Chuck. You have enough unknowns on your plate
without messing with NPG. 

BTW running the cooling system at a higher temp than it is designed 
for could lead to excessive distortion in the rotary engine.

Continental had a lot of problems with their recent liquid cooled
aircraft engines when they tried to run them at a higher temp
than normal. The coolant broke down and left a white powder
that clogged the radiator tubes.

Paul Lamar
 
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