From: Sky2high@aol.com
Message-ID: <5e19c083.247966cf@aol.com>
Date: Sun, 23 May 1999 10:12:31 EDT
Subject: High CHTs
To: lancair.list@olsusa.com
CC: RickArgente@compuserve.com
Mime-Version: 1.0

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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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