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Seems a bit quite on the list, so though I would throw
this out for discussion.
On my way back from Louisiana, I decided to see if I could
determine how close I was to an optimum cooling configuration for my
installation and power.
At 9500 MSL the OAT was showing 46F. At 8 gph fuel
burn (my normal cruise power setting = approx 88 HP) the oil and coolant temps
(no thermostat) were showing 165F. I increased to my max power setting at
that altitude and when things stabilized, I was burning 12.5
GPH (approx 133 hp). I noted that my oil and coolant temps had
both stabilized at 195F. 200F for oil and coolant
are my personal limits for long duration extended power settings - I will accept
upto 220F on coolant for a limited time period during/after take
off.
My conclusion is that my cooling system is fairly close to
optimum (for my installation) in that at full power cruise I am only 5F
deg short of my set limits. I do have a cooling deficit during high power
take off until I hit 120 mph IAS. At that point, the cooling air flow is
sufficient to bring down the temps combined with a modest power reduction after
reaching a safe altitude.
Naturally, cooler OAT would have reduce the temps and
higher OAT would have brought it closer to my set temperature
limit.
Since I normally do not fly at my max power cruise
settings, a case could be made that my cruise cooling capacity is excessive for
my needs at cruise - but, reducing the capacity would then made the cooling
deficit on take off more severe - in fact, unacceptable I am
certain.
Seeing some of the nice custom radiators now available at
a reasonable price from an number of sources such and Ed K (Tech
Welding), I am of the opinion that replacing my decade + old GM evaporator cores
(designed for Freon vice water) would improve the over all cooling effectiveness
and particularly on take off. The very dense GM core fins work best with
high dynamic pressure (higher IAS) available to force air through
them. The wider spacing fins of radiators made for water
would likely permit more air mass at lower airspeeds and enhance cooling
during take off.
Perhaps someday, I'll replace the old 13B with a Renesis
and find more power and that I need a bit more cooling. That would
probably be the time I would consider replacing the GM cores, but after
successfully flying behind them for a decade they are like old friends.
Anyone else have comments about their cooling system -
satisfaction - dissatisfaction?
Anyone there?
Ed
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