I created an almost exact copy of the Kuchemann/Weber perfect
diffuser on my Europa to try and keep my 135 hp EA81 cool.
All cooling on the EA81 is thru the water jacket and none is done by air
cooling on the 912/914 so the ducting has to be good.
Both cooling in the air and ground are very good. I can run the
engine as long as desired at 1800 rpm on the ground without over
heating even on a 100 F day. In the air, water temps to go 200 F
after a 2 minute climbout then drop back to 185 for cruise.
There is a 12" long diffuser section that expands like a bell to
slow and pressurize the incoming air. After the rad, there is a
converging duct that accelerates the hot air back to free stream.
There also is a pull up cowl flap inside the converging section
that allows most of the incoming air to be shut off under cruise
conditions, adding 10 mph by cutting the flow and associated
drag when its not needed. Works great!
Glenn
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