REFLECTOR:High Taxi And Hold Temps.

[Rene Dugas]

MY MT prop is about 3 inches from outlets that were left as long as
possible.  I did no special plenum work and can idle for hours with no
problems in Louisiana.  I was in line at Oshkosh for departure for 1.5
hr. with no heat problems.  Marked breeze through top NACA's with engine
at idle.  I think the huge propeller root on the MT helps.  Climb out
not a problem even at gross with IO 540 straight to 12,500 at 110 knots.
Front and rear cooler.  Rear cooler mounted with a scoop into the floor
of my NACA channel to the plenum about 1 inch high blowing directly into
the cooler.  Hot air from cooler exits below engine through main rear
ports.  My plenum is tight but no special effort.
Rene' 

-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org] On
Behalf Of RJohn15183@aol.com
Sent: Monday, January 12, 2004 1:09 PM
To: reflector@tvbf.org
Subject: Re: REFLECTOR:High Taxi And Hold Temps.

>> I thought the heat would escape up through the ducks and 
out the nacca while idling, like a chimney draft.<<

Well, I had the IO-540 XL with NACA's. I never had any problem on the
ground even in 100+ degree weather in Dallas. (flight was another story
at first until I got the plenum good and tight). 

For ground ops I believe the theory is that your cowl has to come back
pretty close to your prop so that the prop sucks some air through the
system. So when we fit the cowling I left as much of the aft cowl on as
I could. As memory serves the aft edge of the cowl was about 4 inches
from the prop. (maybe less)

As for the chimney effect out the NACA's, when the wind is mild that
applies big time after shutdown. I used to sit in front of the hanger
after flight and watch the "heat waves" rising up out of NACA ducts!

>>Does anyone else have any theories to alleviate the long taxi and hold
heat situation?<<

Another trick you might try if you are not doing it already: Lean very
aggressively in idle. IOW, lean it just as far as you can where it will
still just barely run smoothly. Generally, Less fuel = less heat. Plus
keeping it as lean as you can in idle prevents plug and valve fouling
problems. 
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