---- Ed Anderson <eanderson@carolina.rr.com> wrote:

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

Ed Anderson
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