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Rick,

Do NOT cut an air exit hole in the bottom of your cowling.  This is a high pressure area, especially during climb.

A Sport Aviation article from a year or two ago discussed cooling (I will have to search for the article reference) and how to measure the effectiveness of any changes.  Using a spare altimeter and running the pressure lines thru the cabin heat valve to the engine compartment and getting pitot pressure from the upper plenum and static pressure from a spot below the engine, one can convert airspeed to inches of water pressure differential.  There is a range, below which (5 in?) the pressure is inadequate to get sufficient cooling to occur.  The article shows that some "ground thinking" solutions may be more harmful than helpful.

Just opening up the intakes may result in speeding up the air which might result in pressure fronts being built on the leading edge of the fins, blocking cooling air.  More, but slower air, may be desired.

The air inlet for the LNC2 are fine except that the abrupt end of the inlet causes a tumbling of the air which air blocks the opening making it appear smaller to the incoming air.  Expanding ramps (no more than 12 degrees?, back end of a venturi?) allow for smoother flow of the air and also slowing it down some.  Such ramps raised my pressure differential (I don't remember how much) and increased the cooling.

Seal air leaks in the upper plenum with silicon.  Leaks degrade the cooling significantly.

Be aware that there can be a significant amount of air entering the lower cowl area from around the spinner.  This could lower the pressure differential.  This area needs more investigation.  Check the squashed bug pattern on the cowl in the space behind the spinner.  Anyone else notice such a pattern?

Scott Krueger
N92EX

PS - Rick - Call Me at 630-561-0400

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