Had a long talk with Dick MacCoon (Mr. RPM) at OSH in the Pulsar tent
Anyway I'll get to the point. Dick has a few rules of thumb for cooling
liquid cooled aircraft engines. He says 2 cubic inches of rad volume
are necessary for every HP. That means we should be cooling with 400
cubic inch rads and right now it is taking 500 to 600. We are not
doing a good enough job on the scoops and ducts.

Another rule is the outlet area should be 150% of the inlet area.
Many of our installations are violating that rule as well.
Paul Lamar

Paul,
Well that works well with your current thinking:-
Inlet duct 1/4 to 1/3 of the size of the radiator.
Outlet duct  3times the inlet - or the same size as the radiator.
Given the radiator can be directly exposed to the airstream (current
thinking) with louvers to control over cooling.
Given 400 cu ins is a rad 12" x 13" x 2.5"approx, that's a nice small rad,
(sure better than 13"x18") with a 3.6" x 13" inlet, adds up to a nice neat
package with reduced drag.
George (down under)

Hard to do in fractions.   .25 X 1.5 = .375  or 3/8 th for the exit. 
I think Perry's rad is in that ball park. God knows what it would
do with a proper P51 scoop :)

Paul Lamar
 
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