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Ah, but, That is my point,
Al. You will see a temperature
increase with Evans over a 50/50 even with OEM flow
rates. We are in agreement. But, since Evans has a lower Cp than the
traditional 50/50 mixture, then you either have to heat it to a higher
temperature or flow it faster to remove the same amount of
heat. There is no way around it - one or the other (well, you could do both
{:>).
If your coolant system were removing sufficient heat with
a 50/50 mixture at say a coolant temp of 200F, then using Evans+ (at the
same flow rate), you would need to heat it to 234F to remove the same
amount of heat. The only way you could lower that temperature (and remove
the same amount of heat) is to flow Evans at a higher rate.
But, since our rotary's do not have the same
tolerance for higher temperatures as other engines (apparently Subaru is one) ,
I maintain just sticking EVANS in a rotary is simply asking for problems unless
you increase the flow rate by approx 17%.
Even Evan's web page points out to gain the optimum
benefits you need to increase the flow rate and they even offer higher flow
water pumps, thermostats and radiators to achieve that optimum
level. I am not saying Evans is bad - it clearly offers some significant
advantages - IF your engine is able to take advantage of it - its my
opinion, however, that our rotaries are not able to do that without risk
of damage unless some modifications are made to the coolant system along the
lines that Evans suggested => higher flow rates.
Regarding OEM flow rates. Several folks have
measured the flow rates for their installations but, I don't have any of that
information available, so don't know how it might compare to the OEM flow
rates. I fly without a thermostat which I would think would then permit
higher flow than an installation with a thermostat (even when it is
open).
However, I do use GM cores which do have a smaller
cross channel than a traditional radiator, so you are likely correct that my
flow rate would likely be less than OEM. I keep thinking I need
to get Ed Klepeis make me up some "real" radiators just to see how much
improvement there would be over the GM cores. However, there are others
that are using "real" radiators which should enable them to equal or
surpass OEM flow rates. So hopefully we will at some point be
able to do an apples and oranges comparison {:>).
As always, best regards
Ed
.
----- Original Message -----
Sent: Wednesday, May 30, 2007 8:11
PM
Subject: [FlyRotary] Re: Evans
Coolant
If you were flowing the same volume as the OEM installations, then no,
you would not need to flow more fluid. (You'd just see temperature increase).
Looks like most of you flow substantially less coolant than OEM, so Evans
would be a disaster. We had well proven example in a Subaru. This guy used
3/4" radiator tubing as I recall. Temperatures went to hell a number of months
after first flight. Boil over. He switched to evans and it got substantially
worse. Boil over. This is uncharacteristic. Ended up his unusually long
coolant lines, combined with small diameter tubing, represented something like
80% reduction in coolant flow (compared to OEM). Since evans made it so much
worse, it was obvious he had restricted coolant flow excessively. He changed
to 1" coolant lines, all symptoms permanently disappeared. I believe he went
back to traditional coolant. His radiators are in the wing.
Doesn't matter though, as Evans is only advantage if your engine likes
higher temps. Since it is less efficient. Not desirable for the rotary.
So, all in all, I agree with your statement Ed.
I have mentioned several times in discussions
regarding the EVANS coolant
that to really gain benefits from its use that the
coolant flow would have to be increased to ensure the removal of adequate
heat from the engine. The fact that the EVANS has a 300F+ boiling
point may delay "boil over" but it does little to protect our rotary's
because they are cooked long before that point is reached. In fact,
the 250F boil over of the 50/50 mixture pretty much ensures that if you
reach those temps you have probably cooked your engine. However,
preventing Boil-over (as Al Wick has mentioned) is a worthwhile
consideration.
But, all that aside, my point was that give the lower
specific heat and the fact that the rotary engine is more constrained
temperature wise- means that to flow the same amount of heat out
of your engine per unit time with Evans - you MUST increase the coolant flow
rate. IF you do increase the flow rate with Evans to the point that
the coolant temperatures are within the limits for the rotary then you stand
a much better chance of benefiting from using EVANS.
I happen to notice in reading material on the EVANS
coolant, that the above point is also made by them: This is a direct
quote from material on their web site.
"THE EVANS SYSTEM
Since the Evans coolant possesses
different flow and thermal characteristics than normal EGW, some changes are
in order. First, there is no need to use a pressurized
cooling system, but an overflow bottle is necessary due to the expansion
rate of the coolant. Evans markets 0- and 4-lb. caps for most radiators. The
low-pressure cap is used to keep coolant loss in check on late-model
engines. To totally optimize
this system, a high-flow Evans water pump,
thermostat and radiator should be installed. Working with
data from the field, most late-model
performance cars, unless approaching the 650-hp level, can
reap substantial performance gains with just the installation of the
Evans coolant and high-flow
thermostat. Realizing the huge potential for power
generation through the use of this coolant, Evans has designed many
ancillary components to maximize the potential for late-model fuel-injected engines.
Pulleys to increase stock water pump
speeds, water pump application for TPl, 5.0s and Buick GNs
along with radiators. "
Note the reference to late-model performance cars is a
reference to the fact that these newer engines are designed for and
operate at higher coolant temperatures (more fuel efficiency) than
previous engines (or our rotary engines).
The point is as EVANS points out - there are some
definite benefits to EVANs. However to gain the maximum benefit and
given our rotary's lower temperature limits, I personally believe these
changes are essential if you want a system that keeps you engine
within safe limits.
The changes Evan's mentions include high flow
pumps, pulleys for faster flow, high flow thermostat and high flow
radiators. This implies (to me at least) that if you are going to use
Evans then you need to design your coolant system for its use from the
git-go.
My trouble-making 0.02 {:>)
Ed
-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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