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This stuff real hard to explain in text. But my point was to make sure you
have two cups of air under the cap. Suddenly that brings safety margin to your
system. The air is like a real soft spring. Your pressure gage behaves
differently. It provides much more advanced warning of
cooling issues. You can still operate with high psi cap, but system will
only see as much pressure as you really need.
So 2 cups of air changes your coolant pressure gage into a valuable tool
that's sensitive to most potential failures. Really improves your
understanding of what's happening.
I also have coolant temp and fluid level. When I overheated the engine, I'd
see gradual rise in fluid level, gradual rise in pressure, then jump of both
pressure and temp at boil over point. When I had compression leak into coolant,
I saw 5 second jump of coolant pressure to 24 psi when at full throttle. I never
would have see that if I didn't have the 2 cups of air.
All of these benefits would apply to any type of engine.
I hear you on cooling design issues Bill. Cooling design is a big
challenge. Would be much easier if we could actually see the air flowing thru
core, spilling around sides, bypassing components, swirling. We design in the
dark. If we can't readily measure the things that make a difference, can't
readily change them, then we end up with marginal systems.
FWIW
Al,
I understand your system and it seems like sound reasoning. The
reason I believe many of the Rotary builders run higher pressure is the rotary
does stress the cooling system more than the Subaru. The extra BOILOVER
protection rather than the simplicity of the system wins out. Not that your
system wouldn't work on a rotary. The builder would just have to be sure to
provide more radiator area to be sure the reduction in boilover protection
(provided by higher coolant pressure) wasn't that big a factor. I'm sure
you could and will make the arguement that the radiator area should be sized
as such, and I wouldn't argue, but often people don't consider how much
radiator is needed until they have painted themselves into a corner.
Bill Jepson
-----Original Message-----
From:
alwick@juno.com
To: flyrotary@lancaironline.net
Sent: Mon, 19 Mar 2007
11:10 AM
Subject: [FlyRotary] Re: water boiling point
There's one coolant design that's substantially better than the others. I
discovered it when doing severe ground testing...deliberately overheating my
engine.
Three basic requirements:
1) Place your radiator cap and reservoir above engine. The higher the
better. This allows trapped air in system to rise out of the flow and stay
there.
2) Put a 24 psi cap on the system. You can throw away your overflow
stuff. Not needed.
3) Always keep around 2 cups of air under the cap. This is the key item.
It brings a big safety advantage. It allows you to use coolant pressure to
predict well in advance how good your system is doing. It minimizes pressure.
Mine never exceeds 7 psi. But if something goes wrong, then my pressure rises
and I gain boilover protection due to the increase in system pressure.
If you have compression leak into the cooling system, it shows
immediately as spike in pressure that reaches 24psi. But when all is normal,
you never see pressure above 7 psi. If you have any cooling problem, the
pressure gage will respond quicker than any other sensor.
Sounds like many of you don't have that 2 cups of air. As result,
your coolant pressure regularly reaches 24 psi. Stressing components (radiator
welds actually). It masks compression leaks. Makes it difficult to
predict your safety margin.
Tough to explain this stuff in text, but it's a big improvement in
safety margin. No downside.
To qualify the system, I omit the two cups of air. This causes pressure
to rise to 24 psi. Thus proving all of my welds and connections have safety
margin. Then I add the 2 cups of air and the system never rises above 7
psi unless something goes wrong....whereupon I have extra margin preventing
boilover. Your biggest cooling risk as it cascades and is nearly
irreversible.
On Sun, 18 Mar 2007 11:41:33 -0400 "Tracy Crook" < lors01@msn.com> writes:
Higher coolant pressure will naturally increase the risk of a leak due
to blown hose, loose clamp, radiator tank failure, etc. As in many of
these matters, it is the builders choice as to which potential problem is
most important.
BTW, I do recommend doing a system pressure test at
annual inspection time or after making any changes. I
intentionally over-pressure the system by 50% by hooking a regulated air
pressure source to the overflow port on the cap fitting.
I could be wrong but the likelihood of a blown rotor housing coolant
seal from coolant pressure is very low. If coolant pressure
causes them to leak there was a problem that needed to be addressed long
before the leak happened. Most coolant seal leaks happen at the inner
seal which normally have to seal combustion chamber pressure. Even 30
psi coolant pressure is a very tiny fraction of that.
Tracy (still waiting on Bluemountain)
----- Original Message -----
Sent: Sunday, March 18, 2007 8:21
AM
Subject: [FlyRotary] Re: water
boiling point
My same thought, the higher pressure the better chance of
leaks, for the last 1400 hrs I have been running a 7 lb cap with no
problem, I normally run about 180 for water temp but do see 220 on a hard
climb out on a hot day and when at high altitude its usually so cold
outside that cooling is not an issue.
Ken Welter
Thanks for your reply Tracy!
I did a
google search on water boiling point. Coolant should be
higher,
but it seems that water boils at 183 degrees at 16,000 feet.
But that
is with no added pressure. I could not find the
corrected number for the 12 psi cap.
I wonder how many blown
rotor housing seals are due to higher coolant pressure
?
George Graham
Sarasota Florida
Mazda
RX7 EZ
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-al wick Cozy IV powered by Turbo Subaru
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-al wick
Cozy IV powered by Turbo Subaru
3.0R with variable valve lift and cam timing.
Artificial intelligence in
cockpit, N9032U 240+ hours from Portland, Oregon
Glass panel design, Subaru
install, Prop construct, Risk assessment
info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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