>>can anyone tell me any sense or logic in not having thermostatic control of
the coolant.<<
Nope. However I don't think it would have made any difference to our problem,
which I believe (today anyway) was a matter of heat transfer rates. The coolant
wasn't getting hot but the heads were. When we diluted the glycol the heads
cooled.
With regard to the air cooled barrels, I don't think they are too important,
most of the heat goes through the heads and the piston crown i.e. into the
coolant and the oil. There's another variable for you, the conductivity of the
oil might vary widely, some oil makers claim engines will run cooler with their
product. Could that be why Rotax forbid additives, which might compromise
conductivity? OTOH the air cooled bit might be there in case the coolant
disappears.
I would like someone to tell me what the coolant temp should be, and what EGT to
expect, we get 850 C or more. I'm told that is maybe too hot but no one seems
prepared to be authoritative about it. A fail safe thermostat would be nice too.
Graham
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