Hi Bud,
> I have used the Evans in a stock trigear and have found my CHTs were
> about 15 degrees cooler with the glycol.
Then that trigear was suffering from micro-boiling with the previour
coolant, otherwise it is quite impossible. The heat transfer rate of
Evans is lower than that of water based glycol, no way it can improve
over that. The *only* difference with Evans is the much higher boiling
point. This eliminates micro boiling and it allows you to operate the
engine at a *higher* temperature (also according to Rotax). So far the
concensus on this forum has been that the CHT's get hotter when using
Evans, forcing quite some people with a marginal cooling setup to revert
back to 50/50.
> I cannot imagine that the Evans would be too thick for the Laminova heat
> exchanger as the coolant is basically the same viscosity of the Ethylene
> glycol.
Pure ethylene glycol is too thick as well, but you are supposed to mix
it with water.
Maybe I'm living in a colder climate. On te Evans network I found in
their FAQ a description of exact this problem "some engines overheat
immediately following a cold start due to the lower viscosity of cold
Evans coolant". They offer modified coolant pumps, thermostats, etc. And
they have a new type of coolant designed for motorcycles with improved
viscosity so it flows better through fine radiators.
> I hope not to insult you, but there are three or four types of Evans
> coolants.
I know. There are even more. I have tested the factory recommended NPG+.
But now there appear to be two versions of this NPG+. Read on:
> To my
> knowledge, there is no viscosity difference with any of them and all
> should work with the Rotax and Liminova.
Yes there are differences, to address exactly this problem. I found a
table somewhere but their website is a mess, I have to search for it
again. Take for example their NPG-R:
On one of their websites:
"NPG-R NPG-R is specifically formulated to handle the extreme conditions
of racing and high performance automotive, marine and motorcycle
applications. *The reduced viscosity of NPG-R makes it more compatible
with small tube copper-brass radiators* while providing the superior
cooling of Evans Waterless Coolants."
Also, if you Google you will find references to a product called NPG+C.
Note the "C". Interesting is that it is announced as a product with
lower viscosity, but a preview is not possible and if you click the link
a page with a different contents is shown. It appears that Evans just
removed the references and there are indications they silently replaced
the NPG+ with NPG+C.
If you carefully look at the picture of the can you will see the "C"
behind the "NPG+". My can looks exactly like this but doesn't have the
"C". They now tend to name it "High Performance Coolant" and the can
suggests that it is the formerly called NPG+ but it isn't, it carries
the "C" behind the name.
Maybe Evans is silently replacing their product line and tries to avoid
liability claims from people who experienced problems due to the lower
viscosity. There is a lot of obfuscation going on there. They openly
claimed that the NPG-R variant has a higher viscosity but if you look in
the separate product descriptions they are all listed with the same
viscosity, which contradicts a lot of other information.
Anyway, there are lots of descriptions on the net about pump cavitation,
i.e. the coolant pump drawing itself empty due to the too bad viscosity
of Evans. With a stock radiator it might work, but with a Laminova it
won't. At least not with MY can of Evans NPG+, the one without the C
behind the name.
One example:
"I just got an email from Evans Cooling. They said that the problem with
NPG+ was that it was the viscosity in cold weather coupled with heater
core passages are so small. This prevented the heater from getting hot.
Their solution is to use their new product that addresses this problem:
NPG+C now only available only from their Potstown PA office, same price."
> Are you using the S34 heat exchanger? That is what I thought about testing.
No, a different one (I can look it up if you want), a special
lightweight version. And don't forget you have to plug the center hole
due to the low flow of the Rotax engines. Don't ask me how I know.
If you go testing this, keep in mind that it places a greater demand on
your water cooling. So if this is marginal, fix it first. I abandoned
the stock thick radiator and its ducting completely and have used an
angled thin radiator instead.
For the oil cooling part, keep in mind that the efficiency of the oil
cooler drops of when delta-T becomes too low. It is hard to cool the oil
down to 120C if the coolant is 115C. If you like to be able to operate
the engine near the upper range of its thermal design you still need
some sort of after cooling for the oil. I have used a very small
radiator for it (1/4 size of the stock radiator) and feed it air via a
very small opening through a wedge diffuser.
Benefits of this cooling layout are the higher efficiency due to
elimination of a lot of cooling drag, superfast oil heat up time without
thermostat, and it is impossible to overheat the oil due to the sharp
increase of heat dissipation of the Laminova when delta-T rises.
An in flight adjustable cowl-flap is a must with this design.
Once you get it working it is a hell of a cooling system, with minimal
warm-up time, an extremely broad OAT range, impossible to overheat, and
with far less cooling drag than the conventional setup. Expect to see
some additional knots as a result.
> It almost sounds like the water pump inlet hose was kinked after the
> flush and blocked the flow. Easy done.
There was no kink and there was no air lock. I actually didn't touch the
cooling system at all but just opened the drain at the bottom of the
radiator, and once the Evans was out I refilled it with the old coolant,
and suddenly the cooling system was working again.
To empty the overflow bottle I used a small hose to syphon the stuff
out, what I noticed was that the flow of the Evans through this hose was
far less than what I got when siphoning out the 50/50 coolant. So much
for the viscosity. BTW OAT was about 8C when I was doing all this (dunno
what this is in F, but it is pretty cold).
Frans
|