Tracy and group,
It is very worthwhile to look at the exit size and trim. An an example the on one of the recreations of an original world traveling biplane, BMW provided engines which were mounted in wing pylon or pods. Typical for the era the radiators were upright and large. The rebuilders thought that with modern heat exchangers they would have little trouble cooling the engines. They were wrong! They found that the inlet size didn't matter nearly as much as having a adaquate exit. On the Reno racer Nemesis NXT they have very carefully sculpted the exit to provide better cooling. (and keep the drag down) The inlets are a bit larger than typical but they have very carefully countoured that exit!
Bill Jepson
In a message dated 9/29/2007 9:08:56 AM Pacific Standard Time, tracy@rotaryaviation.com writes:
Larger exit is one thing but has anybody had significant cooling improvement with a cowl flap? When I tried it on the -4 it didn't do any good and I can't recall one that did. I'm going to put one on the RV-8 but only to INCREASE temps in cold weather and high altitudes (and decrease drag).
BTW, the best exit mod I did was to streamline the outlet nozzle (eliminate sharp turns & corners) but left it the same size. This alone dropped my temps 6 deg. F. (which is a BIG deal, every degree improvement seems to be a struggle).
Tracy