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From: Bulent Aliev <atlasyts@bellsouth.net>
Subject: Re: [FlyRotary] Re: Cooling Effectiveness
Date: Sun, 29 Apr 2007 17:58:50 -0400
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>


On Apr 29, 2007, at 4:57 PM, <tonyslongez@cox.net> wrote:

> ---- 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
>> Rv-6A N494BW Rotary Powered

Ed, My takeoff temps are like yours. If I'm lucky to get on the  
runway without waiting and start the roll with 180-190F I'm happy  
camper. But if I have to wait behind few planes, I have to takeoff  
with 200-210F and very soon at 1000 feet start pulling the power back  
at 220F. I'm installing misting system like Tracy. Today bought the  
pump, but have not installed it yet.
In my short hours in cruise I see 160F water and 137-140F oil temps.  
My goal is to do something for the ground an takeoff cooling.
Buly
CZ MK-IV 13B Cosmo NA