Russell Kent wrote:
>
> > Thomas Parkes wrote:
> > Question for cooling system engineers. I've set my EIS to
warn of
> > coolant temperatures above 220 degrees, but I don't believe I've
seen
any
> > data on the actual boiling temperature of 50/50 water/gycol
coolant
under 13
> > lbs pressure. What would be a realistic red-line to use?
>
> A 50/50 ethylene glycol (C2H6O2) water blend boils at 223 degF under
1
ATM.
The
> 13 psi working pressure will raise the boiling point another 40 degF
(
approx).
> 220 degrees (assuming that's accurate) for 13 psi might be fine, but
it
really
> depends on lots of things that are hard to quantify. Where's the
temperature
> reading occuring in the coolant loop? How accurate is the
sender/receiver
system?
>
> Russell Kent
You might try making that a 90/10 glycol mix. Much better heat transffer.
And
run a 22 pound cap.
Lynn E. Hanover
Thomas Parkes wrote:
Everyone:
Thanks for your comments and information. I have been considering a higher
pressure cap. Now its almost certain. In the meantime, here's an update on
my second flight in the traffic pattern:
Thursday, Feb 20. Flight #2: 20 minutes in and above the pattern.
For this flight I pre-leaned the mixture more than on flight #1, trying
to get gray instead of black exhaust residue. Wrong move. EGT went to 1860
and wouldn't decrease below 1800 even after power was reduced to 20" MP at
1500 AGL. Max coolant temp was 222 degrees, oil about the same. The good
news is that both coolant and oil temperatures stabilized in the low 190's
at 110 to 130 knots, with cowl flaps open.
Now for the coolant pressure steep learning curve. After engine start
the coolant pressure increased slowly to 12 psi on my Grand Rapids Tech EIS,
as usual, and remained there through take-off and climb. Level in the
traffic pattern it decreased slowly to 8 psi and remained there until
reducing power for landing. After exiting the runway it was again reading
zero.
It is slowly dawning on me that these readings may be quite normal. The
only difference from one of my cars is that they don't have a coolant
pressure readout to confuse the issue. Here is my current thinking: As the
engine warms up and coolant expands under pressure, pressure is regulated by
the pressure cap, which sends excess coolant to the recovery tank. During
cruise, as the engine cools, pressure decreases to a moderate level and
maintains that level until power is reduced for landing and the engine cools
even more. Now the pressure gradually reduces to below ambient, which shows
as "zero" on my EIS (doesn't read negative values), and coolant returns from
the recovery tank. Sounds simple enough in the calm of post-flight
analysis, but I sure didn't expect to see a zero indication on that first
flight! Am I missing anything here?
To answer a couple questions you people posed. My coolant pressure
sensor taps into the water pump outlet housing between the thermostat (yes
it is still installed even with cowl flaps) and radiator cap--just before
exiting to the radiator. It is measuring the hottest coolant. The radiator
cap is the high point in the system, about level with the recovery tank.
Two flights, no coolant loss, no oil leaks. Yes, except for low rpm
Ross gear lash, the engine is definitely smooth--:) And with this Garrett
turbo pulling 30" MP, it really responds with gusto--:)) My pop-off valve
is set for 32", so this is essentially a turbo-normalized system.
A note for other Lancair ES builders: My neighbor, Ken, also built an
ES, starting a year after me. But he installed a conventional IO-550
engine, and so was able to finish before I did. During his Phase I
testing, he encountered a harmonic "buzzing" throughout the airframe which
began immediately after lift-off and varied with power settings and
airspeeds. He tried everything Lancair, Continental and Hartzell could
suggest to isolate the problem. Nothing worked. Finally, in a moment of
inspiration he jacked up the nose gear, removed the wheel fairing, and spun
the nose wheel. It kept spinning. You guessed it, the bearing had loosened
in use and airflow across the bottom of the tire kept it spinning after
take-off. The harmonic buzzing was due to the nose gear strut being mounted
to the engine mount, which was transmitting engine vibrations and the nose
strut was acting like a tuning fork with a spinning wheel attached. He
re-tightened the bearing to the requisite spin resistance and viola!
Problem solved.
I mention this because, with everything else going on during flight #2,
I thought I sensed a lower magnitude but otherwise similar harmonic in my
airframe. My plane is down for a few days while I check this out and
upgrade a couple details on the turbo oil drain system. Thanks to everybody
for the help and encouragement. Couldn't do it without you.
Tom Parkes
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