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Message
John, your heating does not seem that unsuall to
me. While it, of course, varies from installation to installation, if I
run WOT from more than 2-3 minutes my coolant temp will
be pushing 200F. Now, my radiator ducts are removable and on the
ground that helps my cooling a great deal. So if I plan on doing a lot to
high power run ups I pull the hinge pins and remove the ducts for more low speed
air flow across the radiators. I think a 15 minute 4000 rpm run up would
cause my engine to overheat on the ground depending on OAT.
Now if I restrict my rpm to 3000 or less then it
will stablize around 180F, again depending on OAT.
I ended up putting louvers in my Cowl as the
heat buildup even after engine shut down would be enough to make the top of the
cowl too hot to place your arm on. I figure the hot air need somplace to
get out from under the cowl than the bottom.
I tried putting thermostats in my engine on
two occassion and ended up overheating the engines until the metal
pinged on cool down (ugly sound). Fortunately no damage even though it
went to 250F on one occassion. So I decided just to leave the
thermostat out. Other folks apparently use them with apparently great
success. My cruise oil and coolant temp varies between 160-190F depending
on OAT but normally it stabilizes at 180F.
I generally taxi out and do a run up to around
3500-4000 while taxing to check both ignitions are functioning with
Controller B, then switch back to controller A and reducing throttle to a fast
taxi around 2500-2700. At the end of the ruwnway, I then swing into the
wind and do a WOT engine check at 5200rpm+ for fuel, and oil pressure, fuel
flow rate and air/fuel ratio indication. If all meet my critieria then I
release brakes and launch.
I think I would taxi to the end of the run way, run
as high an rpm as you brakes will hold and wait until the coolant temps reaches
170F and then accelerate until you need to shut down to keep from becoming
airborne (or go off the end of the runway) then check your coolant temp.
It is not uncommon for the engine to put out more
waste heat than the cooling system can handle on take off an initial climb
out. So you are running a cooling deficit until you get sufficient
airspeed to reject the waste heat. For the RV thats approx 120MPH TAS,
Should be somewhere near that for a canard or perhaps a bit higher if you
ducting is a bit less than optiumum
FWIW
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
Sent: Wednesday, March 31, 2004 8:34
PM
Subject: [FlyRotary] Requesting more
thoughts on cooling
Guys,
I'm signed off and ready to fly, but I'm a
little concerned about cooling issues. I don't want to melt anything in the
first go around the pattern.
I'm finding that the engine gets REALLY hot
after about 10 - 15 minutes ground running, and I'm wondering if that's to be
expected, or if I have a cooling problem. Maybe I should just taxi
gently to the runway and launch to get airflow as soon as
possible.
For example, today I ran it up and down the
taxiway for a few minutes at fairly low speeds and around 2500 - 3000rpm. Then
I did some static runups (maybe 3800 - 4000 rpm - all the brakes will hold)
and some EC2 tuning. Then I did some mode 1 programing at various rpm.
During this run I watched the water temp gradually go up until
it was over 200 and I shut her down. The oil was still down around 140 - 160.
I took the cowl off and found that everything in the engine compartment was
HOT. Radiator, oil coolers, hoses, intake, the cowl itself. Apart from giving
my cowl a REAL GOOD post cure I dont think I've done any damage, but this
doesnt give me a lot of confidence about whether I'll make it around the
pattern.
The thermostat is now in place, and I get the
feeling that I'd be much better without it. Once the engine gets a little hot
the water temps seem to "run away" if I'm producing any kind of power. So...
to remove the thermostat [3rd gen rew engine] I have to remove the water pump
and have the by-pass hole welded shut - right?
Do you 13B drivers tend to just taxi out at
low rpm then launch? Would your engine overheat if you did a 15 minute medium
power runup? I'd appreciate
any general thoughts, or comments on how much ground running I should expect
to get away with before the temps get too high. Anything else I should
check?
Regards,
John Slade
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