My focus is on flight safety. I found great value to having appx. 1 cup
of air at the top of my cooling system. With the cup of air, my system
never exceeds 8 psi. So this allows me to measure cooling system
integrity (using psi). Without the cup of air, the pressure reading
always rises to 24 psi, then fluctuates. This prevents me from using
pressure info in meaningful way.
With cup of air, if I apply full throttle and have compression leak into
cooling system, I would see spike to 24 psi. Without cup of air, I would
not notice that spike.
With cup of air, the closer I get to 24 psi, the closer I am to serious
condition. Pressure is an excellent predictor, fast responding and
measuring more than one characteristic.

On startup, my cooling sys is always 0 psi.  5 min later, before takeoff,
it rises to 1 psi. On takeoff, it gradually rises to 7 psi. All pressure
changes very gradual.

So from a safety point of view, I would never consider going back to the
full coolant system.


-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html



On Sun, 26 Jun 2005 10:05:16 -0400 "Ed Anderson"
<eanderson@carolina.rr.com> writes:
> Good question, John
>
> If the analysis is correct, it may indeed be better to have a small
> cushion
> of air at as an absorber.  All of my coolant components take at
> least 250
> psi (radiator cap and water pump seals excepted).  The only concern
> I have
> with higher pressure is blowing out the seal around the water pump
> shaft -
> don't have any idea how much pressure that might take.
>
> Ed