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Good question, Al.
I have little hard data, but here are some of my
conclusions.
I believe the old coolant maximum temps were based
on the early 13B blocks using stock coolant O rings as the first
limit. This was a limit of around 210F. I believe that when we went
the TES O rings that temperature limit was moved up. I believe that the
second limit is coolant temps around the spark plug holes (excess temps causing
cracks in the housing). I don't know what the limit was based on that -
however, the racers found that by grooving the coolant passages in and around
the sparkplug are that much better heat removal was achieved.
My opinion (you know what that is worth) is that 210F on coolant is no problem
for any duration less than 30 minutes (perhaps even longer). I have
repeatedly had coolant up to 220F on take off (generally less than 5 minutes)
with no apparently adverse affects (at least no short term ones).
The oil temps restriction I have a less of a handle
on. 250F limit for the oil pan sounds like a fairly high limit. I
suspect that before we started using the viton oil O rings (on the rotors) that
those O rings likely constituted a lower limit for oil. Apparently the
rubber plugs in the corner seals will go if the rotors get hot - but, not
certain any damage results. So the only temperature critical thing I
can think of on the rotors are those oil "O" rings. Now at some
temperature point the oil turns to water and no longer provides adequate bearing
support - but, I would assume synthetic oil raises that limit a
bit.
Here is some information I have found over the
years
Racing Beat
Coolant (out of engine) maximum 210F
Oil Out Of
Cooler Maximum
200F
Mazda Motor Sports
Coolant (outlet Side) Maximum
205F
Oil (Pan
Temp) Maximum
250F (In the pan)
From my own Personal
Experience
Maximum Ever
Max ever on oil Temp 240F (first
Flight) 4 1/2 Minute Duration so over temp probably for 4 minutes
Max ever on Coolant temp 240F(First
Flight) . No damage detected afterwards - except my seat
cushion.
These are some data points on take off and are
generally less than 5 minutes duration and frequently less than 3 minutes -
after 120IAS is achieved, temperatures start decreasing. Normally cruise
burning 8 gph is 165 oil, 165 Coolant. All coolant temps taken at
thermostat housing, all oil temps taken after oil cooler.
Occasionally on 90F+ Days
Oil temp 210F
Coolant 220F
Frequently on 70-90F
days
Oil temp 200F
coolant 210
F
Once OAT drops below 65F both oil and coolant stay at
or below 200F on max power take off, with the oil being around 190F and coolant
200F.
For what its worth
Ed
----- Original Message -----
Sent: Saturday, June 09, 2007 1:56
PM
Subject: [FlyRotary] Oil temp limit
I guess we’ve had this
discussion before but to me it still seems like a grey area.
The limit has to do with
temperature, time, and limiting component.
At typical cruise conditions I
have coolant temps of 160-170F and oil temps about 20 degrees higher.
Short term climb out (1000 – 2000’) I see oil getting up 215 -220 and
coolant around 200. If I continue climb, I need to reduce power to keep
them at those levels; which means climb rates of 500-700 FPM with OAT of 65F,
and maybe a bit less if OAT is higher. I don’t like being limited to
that climb rate when I have power for considerably more; but the real question
is: Is that temp level an issue if sustained for 10-15 minutes? And what is it
affecting?
I expect to make some
modification to improve airflow through the cooler, just deciding if it is
urgent or if it can wait for another 10 -20 hrs of flying. Anytime I go east
from my airport I have to climb from 1400’ to about 7000’ to clear high
terrain.
Thanks,
Al
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