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1. 10:48 AM - Hot oil cooler ideas from Phoenix (MPPalmer@aol.com)
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| Subject: | Hot oil cooler ideas from Phoenix |
Location, location, location. I've moved our oil cooler inlet for better
cooling. Per some aircraft we saw at OSH while building, I thought I was being
"cool" by putting the intake for our cooler on the pilot side bottom of the cowl.
The thinking was that the prop would spin air into the cooler (left side of
lower cowl) and that, being on the bottom, the cooler would get more ram air on
climb out, when you need it most. (And on the other hand, it would
automatically "close off" in level flight, due to the boundary layer increasing
in
cruise, bypassing the scoop. I have since moved the NACA to the copilot side. MUCH
better.
First, our cowl scoop (carbureted Glasair II) blocked any air rotation from
the prop. In essence, I think I had a dead zone on the pilot side of the lower
cowl. Second, there is no ram effect with a NACA. I have a NACA for engine
intake air and it's remarkable, but those things don't see any ram pressure at
all! (Probably by design.) I do not see any increase in MP from a climb attitude
to a screaming dive. I still like the bottom location of the NACA for the
closing, boundary layer feature (if any). i.e. lower cooling drag in cruise.
In our hot Phoenix summers, we will see one needle width short of redline on
climb out (guessing about 230 degrees). That's on a tricked out 320 (170 HP?)
with a SW oil cooler. It quickly comes down to vernatherm temp 180 - 190 on
leveling out. (We run WOT, 2400 rpm, LOP. LOP helps a lot.) Interestingly, when
we slow to 15 inches for pattern, the oil temp will come back up to almost red
line! A combination of lower differential air pressure across the cooler due
to the slow airspeed and the oil not moving through the cooler at reduced
engine speed.
Things to check: Is the oil cooler flowing correctly internally? (Was it new
or used?) Pacific Oil Coolers can clean them. They claim flushing with solvent
doesn't really do it.
I've seen temp changes when I change the static oil pressure. There's a
balance between having oil flow too fast / too slow through the cooler. Try
increasing / decreasing your oil pressure to see where you are.
Are your oil lines okay? If rubber, any broken flaps inside the hose? I
switched to Aeroquip 601. Indefinite life, much more flexible and very smooth wall.
Getting air OUT of the cooler is as important as getting air in. Is there an
unrestricted path from the output of the cooler to the bottom of the cowl? Is
the cooler in a low pressure area? If you're side mounted, I'd run a giant
SCAT tube to the bottom of the cowl to see if that helps the air flow out the
cooler. Or move the cooler down to the bottom of the cowl, where air can come in
from a bottom mounted NACA directly into the cooler and quickly exit out to
the lip of the lower cowl scoop.
Ted Setzer took us for a ride in the factory III years ago at a summer
airshow here. Red line all the time on the oil temp. Ted remarked that there were
better locations for a cooler than the stock factory right side of the cowl. Not
being a III driver, I don't know where they exit that air, but I've seen some
funky reverse NACA's (bumps out into the airflow) at OSH on some III's as
they try to ameliorate the problem.
I helped a guy with a tricked out Glasair I, 200 HP+ engine who has the right
side mounted cooler. He lives in Ogden, UT and says he gets very hot on climb
out too. I made a fiberglas plenum to direct air from his inlet to the
cooler. I don't remember if I made a similar plenum to direct the air out the side
louvers. Unfortunately, his Whirlwind prop blades delaminated and he hasn't
flown since my mods.
Hope this helps,
Mike Palmer <><
<BR><BR>**************<BR>Gas prices getting you down? Search AOL Autos for
fuel-efficient used cars.<BR> (http://autos.aol.com/used?ncid=aolaut00050000000007)
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