Finally got around to finishing my cooling inlets. (pictures attached)  Up until now they were simply round pipes sticking out of the cowl.   The pipes are still there but they have properly shaped bellmouths on them.   The shape and contours were derived from a NASA contractor report (NASA_CR3485) that you can find via Google.  Lots of math & formulas in it but I just copied the best performing inlet picture of the contour.   Apparently there is an optimum radius for the inner and outer lip of the inlet.   There was no change to the inlet diameters of 5.25" on water cooler and 4.75" on oil cooler.

The simple pipes performed adequately in level flight at moderate cruise settings even on hot days but oil temps would quickly hit redline at high power level flight and in climb. 

The significant change with the new inlet shape is that they appear to capture off-axis air flow  (like in climb and swirling flow  induced by prop at high power)  MUCH better than the simple pipes.    First flight test was on a 94 deg. F day and I could not get the oil temp above 200 degrees in a max power climb.    They may have gone higher if the air temperature remained constant but at 3500 fpm the rapidly decreasing OAT kept the temps well under redline (210 deg F).

I have an air pressure instrument reading the pressure in front of the oil cooler and was amazed at the pressure recovered from the prop wash.  At 130 MPH the pressure would almost double when the throttle was advanced to WOT.   That did not happen nearly as much with the simple pipes.  

These inlets ROCK!

Tracy Crook

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