Hello Ira
The info provided about flammable liquids was not a full discussion on the
Pros and Cons of Evans, but was results about the flammability which I
wanted to see and feel actual results for myself before I went flying with
it in my cooling system. The results were just about what I expected. I
added a test to see if 100LL in fact does ignite as easily as Mobil 1 when
put on a hot muffler (it does not, Mobile 1 ignites a lot easier).
There are Pros and Cons about Evans. I spent several days in contact with
folk at Evans when Rotax first came out with recommendation. I have posted
results and my conclusion in the past, but will restate:
The folk at Evans were a bit shocked that Rotax made such a quick and bold
jump with so little testing in their opinion
It is true that Evans can run with a Zero pressure coolant pressure cap,
but that is when the system design has cap located on the vacuum side of
the water pump. The Rotax 9xx has the pressure cap on the pressure side of
the water pump. You should not run a Rotax 9xx with a zero pressure cap.
On my 914 install, I will run Evans with a .9 bar cap.
The ability of Evans to transfer heat is not as good as water, or quite as
good as a 50/50 mix of water and Ethylene Glycol. Evans on most of their
applications recommend increasing flow rate of water pump or increasing
radiators ability to dump heat to compensate for this. I don't know of a
high flow Rotax water pump for use with Evans, but may be a good idea??
Evans also knows that Evans is more viscous and the radiator should not be
too restricting, or it needs to be replaced with one less restrictive, I
have the info of core requirements if anyone needs, but the Stock Europa
Radiator seemed OK when I measured it.
Evans will run a bit hotter than a 50/50 mix due to a poorer ability to
carry away heat (Perhaps 10 degrees F, what I have read anyway about
Europa Monowheels). I am willing to accept this downside. I am installing
a Rotax cooling air baffle that I think will just bout negate the slight
higher temp Evans will run over a 50/50 mix.
On a 914 with intercooler, and a monowheel to restrict cooling flow on the
ground, boil overs on ground and in the air are not a welcome occurrence.
In addition when you are making some BTUs at altitude (an intercooled 914
can more easily do than normal aspirated), remember that the pressure cap
for the cooling system is not altitude compensating, thus at altitude you
will have less pressure in the system than at sea level, and less air to
cool things. (Side note, this lesser pressure at altitude and higher oil
temperature can cause oil tank to not condense foaming oil and a very
undesirable oil pressure drop can occur, same goes for 912 or 912S). Even
though you could have an overall acceptable coolant temp and cylinder head
temp there can be pockets of boiling coolant that have very little ability
to carry away heat and can cause hot spots a gauge will not reveal. Evans
has a much higher boiling point, and even if you did get it to boil, it
still will carry away a significant amount of heat (Think it is 50% ??) of
what it is capable of when not boiling.
Evans does not have to be changed, and will not hurt aluminium. Use of
Silicone coolant and radiator hoses, should negate having to replace every
5 years, not a trivial job.
Should a leak occur where pressure was reduced, Evans would conduct at a
lower pressure better than a boiling 50/50 mix.
If you developed a coolant leak, landed and repaired and could not find
Evans, You could mix up to about half with Ethylene Glycol to get you
home, but then should flush and replace with Evans 100% (according to
Evans Tech.).
Evans about a year ago would test your coolant (for free) to make sure it
is still up to snuff (CT office).
I fully agree that keeping the heads of a 9xx cool so as not soften them
is a worthy effort. If I find that there are conditions that temporary put
motor hotter than I care for, a water spray onto radiator could help with
that, no matter Evans or 50/50. I am also going to try and optimize
cooling intake and exhaust for radiator, intake no larger than needs to
be, exhaust adjustable cowl flap (Gilles has great info on cooling
dynamics). If I see that things are not quite acceptable, an easy thing to
try a 50/50 mix (I also have a 1.2 bar cap).
Another subject, but keeping the oil hot enough, and warming it up before
you make some BTUs is a worthy effort. Especial desirable when performing
a restart after soaring. I am installing a Mocal oil thermostat with -8
fittings. It always allows a path to and from oil cooler, so if it failed
with valve opened or closed, you would never starve for oil (like some
others I looked at). What the Mocal does, is allow a easier bypass path
internal so instead of all the oil going through the cooler, for the most
part takes the easy path. there is however some oil going through the
cooler at all times. I will plumb my oil system with Aeroquip 498 and 598
(same hose, black or blue) and use mostly Aeroquip steel crimp on
fittings. Will use McMaster 90 degree stainless large radius thin wall
barbed tube fitting for bend needed. The 498 and 598 have same ID as
FC332, has a slight tighter bend radius ability without kinking (slight
larger OD, not much), and I like the crimp on steel fittings better than
the brass or aluminium push on barb fittings. The ID is very large for a
-8 hose, and is good for 300F on inside and 250F with air.
Ron Parigoris
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