Ed

You asked if I had divided my inlet plenum to divert more of the water cooling air into the oil cooler.  The attached picture shows a 1/8 inch thick foam board with a thin layer of glass cloth covering it.  I installed the diverter and flew several times.  No measurable improvement was noted.  It probably helped some but I needed quite a bit more!  The picture also shows some white vanes I installed on the rear half of the oil cooler - left side in plenum.  I had thought that the air flow was having to make too big a direction change at the radiator face.  The vanes did not improve cooling of the oil significantly either.  Bobby H. brought over a spare radiator and we tested it on our improvised wind-tunnel at 90 deg. to the air stream and 30 deg to the air stream.  The duct leading to the radiator was shaped so that the radiator surface area receiving the air flow was kept the same in both tests.  Using a very sensitive velocity measuring device Bobby provided we found that the exit velocity was 28.7 mph at 90 deg - in this test the air went straight through the radiator fins.  With the radiator at 30 deg. to the air stream the air had to turn 60 deg to go through the radiator.  The air speed behind the radiator at 30 deg was 28.0 mph.  This test proved my suspicion that the radiator fins were causing turbulent flow at the surface of the radiator was WRONG!  This was Good News to me because it meant my oil/water cooling system probably could be made to cool without major redesign.

I have made 3 flights recently with static pressure, dynamic pressure and temperature probes under the cowl.  After reviewing the data, I made a change to the cowl outlet area and flew again.  The cooling was GREAT.  My oil/water cooling system will work.  I'll post pictures and results soon.  I need to do some more flight tests to determine if I will need any sort of cowl flap or not.   My water was much cooler and the oil stayed below 210 deg. F. while climbing at 25 in MP. to 6500 ft.  Also additional tests may show that I can blank off some of the water radiator surface to force more air into the oil cooler.  Only testing will tell!

Some time ago I modified the James cowl by cutting the upper inlet hole just below the spinner.  This opening provides combustion air to the engine.  A fiberglass plate was installed to separate this combustion air inlet from the oil/water plenum.  This increased my manifold pressure in cruise significantly.
Ed Anderson wrote:

 

Ed