I am interested in your thoughts regarding Evans Waterless Coolant For
rotaries and older classic cars (1950s).
Have you had experience with the product?
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john hedblom
People have used it in aircraft.
What is questionable is the coefficient of heat transfer between the
coolant and the metal. I would test it with a thermal couple "cyl"
head temperature device. Just because the coolant is temperature x
does not mean the metal is being cooled.
Paul Lamar
There are 4? types of Evans coolant. They been used for drones, Rotax
engines, and it is in many heavy trucks, race cars and regular cars.
This stuff boil at 375 F, so there is less chance of bubbles forming
at
hot spots in the cylinder heads for example, and pressure is not
needed
for raising boiling point. The stuff is expensive, although it isa
lifetime coolant, the rest of the cooling system is not lifetime. Loss
of a hose or water pump seal, and you will lose the stuff. No coolant
pressure make this less likely.
In engines, the most important thing is the coolant cannot boil, it
can
be higher temp. higher temperature also means the temp. difference is
greater, increasing cooling efficiency.The problem comes when the
system
temp is at say 250F, long before that, hot coolant already boiled and
bubbled at hot spots, making uneven cooling. This is where Evans
shines.
This coolant is not water, it will cause less corrosion. In your car,
the theoretical boiling temp is 256F when you have 50/50 mixture of
water and anti freeze and 15 PSI pressure. If it gets near 240F I
would
have felt very uncomfortable. I would start trying things like shut
off
the A/C, slow down, and turn the heater on.
Evens used to sell a flushing liquid, may have been discontinued. It
is
important to get rid of as much water as possible when changing over.
Those at the southern states can drive with the rad cap loose, till
the
water evaporate away.
Tony Lam
My first off airport landing was caused by me buying into that
logic.
I
had a small leak in my cooling system and wanted to minimize coll
ant
pressure to get the plane home. I switched over to evan's coolant
and
installed a 7psi radiator cap. It turns out that 7 psi was not
enough
and
all the evans coolant boiled out via the overflow. The engine ran
for
a
couple minutes until the rotor housings melted. I landed on Hwy 395
near
Bishop.
I still don't use Evans Coolant. The fact that it can get to higher
temps
before boiling is of no use to us. We want our coolant temps down
around
180. To that end, standard coolant does a better job. There are
probably
some excellent applications for Evans, but high duty cycle Mazda
rotary
engines are not one of those applications.
--
David Leonard
Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
I live in Queensland and only use additives for anti corrosion,
if you need antifreeze OAT will help with cooling. Most glycols
recommend 50/50 max due to the effects of reducing the water
content, what is the point of a higher boiling point if you
are going to see those temps, water has good heat absorption
properties and is readily available, draws off heat better
and is proven. If you are going to switch then test it near
to the airport or in your car first. Those that ignore history
are doomed to become history.
Graeme Riley
I am curious, David Leonard. Did you ascertain that ALL water was
removed
from the cooling system? Leaving in more than 3% water will negate the
advantages and water boils! You cannot add Evans to top-off the header
tank.
john hedblom
I must admit that retained water is a possibility. I drained the
radiator,
engine block, manifold, and reservoir but there would have been small
pockets of coolant left in the engine block.
I am not trying to say that Evans will not work for our application or
that
it directly caused my engine out. Indeed, I flew with it for about
100 hrs
after getting my plane back in the air until I realized it offers
almost no
advantages while coming with several significant disadvantages:
Advantages:
Waterless so probably has better corosion resistance.
Better freeze protection.
Disadvantages:
Lower specific heat means you will need a bigger radiator and the
upper end
of possible heat rejection from the engine is lower than with standard
coolant.. or, for a given installation the temps are going to run
hotter.
Resistance to micro boiling may mean that it is not as good at removing
heat from the hottest parts of the engine.
Field repairs of the cooling system become much more difficult... The
stuff is pretty close to mail order only. And I have done many many
field
repairs requiring at least a coolant top off.
A higher possible running temp is of no value because the rotary wants
to
be at 180.
Running at low pressure is of limited value if any. A healthy cooling
system easily handles coolant pressures and sensing that pressure is a
good
verificarion of a healthy cooling system. It does not run at a low
enough
pressure to compensate for a significant leak.
It is more viscous than normal coolant. Mfr. recommends changing out
the
pump. May be very tough to circulate at low temps and will carry out
heat
more slowly when at operational temp.
I was a big advocate on this list several years back. But changed my
mind.
Evans would be a good choice if you were going for some sort of high
altitude record.
David Leonard
Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
What will be the difference in viscosity and ability to remove heat
between 50/50 antifreeze and Evans? It would seem to me that no water
would
REDUCE the occurrence of "Micro-boiling" if the boiling point is so much
higher for the Evans. Evans recommends using their re-usable
pre-treatment
to absorb the last of the water in the system. More thoughts?
john hedblom
I run Evans in my RX-7. I have had other issues that have kept me off the
road so I can't really offer a sincere opinion about its benefits one way
or the other
However, in regards to switching to Evans, it is compatible with standard
ethylene glycol antifreeze, but NOT water. So you can switch by: A)
drain
as completely as you can, B) put a gallon of pure standard antifreeze in
there, wiz it up and drain again, then C) go to Evans. This will suck up
all remaining water. Any remaining antifreeze there will be nearly pure
antifreeze that is compatible with Evans. I don't recall the
pre-treatment
John mentions when I switched, but perhaps that is something new (probably
is a bottle of cheap standard antifreeze!)
-- James
One of the advantage of NPG would be the ability to run 250F
coolant temps which would allow much smaller radiator and
cooling drag. Having to run low coolant temps and/or high
pressure is a sign of boarderline cooling of hot spots with a
water based coolant.
The metal temps have to be kept under
control by a high unrestricted coolant flow to make up for the
reduced heat capacity compared to water. Might take more than
the stock water pump. The block mods to aid cooling would help.
I think the Wankel cooling failures are due to steam blanketing
or air in the cooling passages in the hot parts of the engine.
Steam and air are not good for cooling and will cause the temp
to spike leading to damage. With the combustion chamber
thermocouples installed it can be tested safely.
Murry I. Rozansky
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