Subject: [FlyRotary] water flow restrictor

Although I would probably prefer to run a thermostat, my water pump
housing lost the ability to house a thermostat when it got chopped down
to size.  Do I need to put in a restrictor?  If so, how big should the
opening be?

David Leonard

Putting  flow restriction in an aircraft application where you want
minimum radiator size and weight is a bad thing; in my opinion, of
course.  The more flow the better - gives a lower temperature drop
across the radiator, therefore higher average radiator for the same temp
going back to the engine.  

The idea of a flow restrictor is to provide higher pressure in the
block, therefore increasing the boiling point somewhat; and provides
back pressure to the pump which may reduce the risk of cavitation at
very high rpm (like over 6000).  If you don't mind a larger radiator,
OK.

Size the radiator for about a 30F drop from inlet to outlet. Let the
radiator provide the back pressure in the loop, maybe take advantage of
double pass.

Al