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FW: [c-a] Orange County CA Cozy Tax Nightmare
After careful consideration,
I think I am going to switch to Evans NPG (100% propylene glycol) during my
annual this year when I flush the cooling system. Here is how I see
it:
Disadvantages:
1. I will probably run a
higher cooling temp, about 20-30deg higher best I can tell, This will
put my hottest temps up around 250F. I think the coolant o-rings should be
able to withstand that. Otherwise, the increased temps will improve heat
rejection and possibly BSFC without other negative impact. Running higher
coolant temps should also partially offset the decreased specific heat of the
NPG (better temperature difference in the
radiator).
2. Initial cost and hassle
flushing the system.
3. Higher oil temp. -
Oil temps are not a problem for me, if anything I would like to see them up into
to 180 range (currently 140-160).
Advantages:
1. No risk of boil
over. I had one in-flight boil over when using 50/50 EG. That was a
real pain. Once it gets to boiling over it is very difficult to get it to
cool down, and it can be hard to find water at some airports. Also, a
small leak in an EG or water system will drop the pressure and cause boil
over very quickly.
2. Antifreeze. Running
water with water wetter did decrease my temps by 20 deg, but I could not leave
the plane parked overnight in the mountains for fear of possibly freezing the
coolant. So before flying to any place cold I had to drain out the water
and add EG. That was a real pain, and now my temps are back up near the
boiling point of the water /EG mix.
3. Longer coolant life and
better corrosion control. Evans clams NPG+ will last the life of the
engine, but I will obviously replace it every 5 years when replacing the cooling
hoses.
4. Non-toxic. I am
frequently dripping EG in the hangar every time I do work on something.
Would prefer something non-toxic.
5. Low pressure cooling
system that does not change pressure with altitude... I eventually plan to
get into the flight levels but that would mean that my boil over temp drops
dramatically.
6. Better control of
nucleate boiling. Not sure if this is good, bad, or indifferent.
Evans claims it significantly improves the margin of safety for detonation and
allows increased spark advance. Others claim that nucleate boiling is
important for cooling very hot spots.
Comments? Anyone have
real life experience with NPG they could
share?
Dave
Leonard
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