Perry Mick wrote:
I got the modified oil cooler installed. I flew Monday morning, but could
only go to 1500 feet because of low overcast. Oil temp only reached 182. It
was a cool day, but this is about 10 to 20 degrees cooler than normal. After
having oil temp problems for the last 4 years I do not attribute the
improvement to the new mounting method, but to the 86 oil cooler I was able
to use. I'm convinced there is something different on the internals of the
82 vs. 86 oil coolers, and the 86 is more effective. The ports on the 86 are
odd, so if they are not convenient in some installations I would recommend
plugging them, drilling a hole in the tank on the convenient side, and
welding on a 1/2" NPT aluminum half-coupler available from McMaster Carr. I
was going to do this a year or so ago, but didn't want to go through all the
work without knowing for sure there was an internal difference. The outside
dimensions and appearance of the coolers is the same except for the port
location. The 82 has 8mm ports same as the front of the engine, and the 86
has 10mm ports same as the rear of the engine.
I couldn't fly yesterday morning or this morning because of fog, but will do
one more test flight to verify it is cooling well. Then I want to relocate
the oil cooler so the right side of it adjoins the left side of the lower
cowl, and the inlet will be more like an armpit. And I will close up the big
hole in the upper cowl that is no longer required.
Perry
Perry, please measure the pressures on the face in four equal divisions
along the oil cooler for me. Should be easy with your new digital camera.
Unfortunately you made two major changes at the same time destroying the science :)
Unfortunately I had to, with the oil cooler crammed completely inside
the cowl with the ports at the front, the 82 is the only one that would
work. With the leading edge of the cooler in the breeze and the ports at
the rear, the 86 is the only one that would work.
I am sure the back side is OK but you never know so if you don't mind
put some pressure taps back there as well.
One hint that it is ok, oil temp dropped to 150 during descent and
landing which is normal, but increased to 170 during taxi back to the
hangar. This is unusual but I think it's because the cooler is farther
forward now, farther from the ductfan, and there is no exit duct back
into the ductfan.
Are you using the foam ramp or just the blunt end of the cooler?
I think you could come straight forward with the ramp instead of
tilting it down like that. Should cut the drag slightly.
I flew with just the blunt end of the cooler. I glued in the foam ramp
yesterday so if I fly this morning that will be in place.
Also think about adding a boundary layer air bleed when you rearrange it.
Check and see if this configuration has affected your top speed.
Probably not a detectable difference.
If you remove the fittings and look inside that 82 cooler you should see
some turbulators in the tubes. If not that may be its problem.
That is the only thing I can think of that would make such a major
change in its cooling ability.
Paul Lamar
That's my guess as to the difference. The 82 was a 12A engine of course.
Maybe they had to improve it effectiveness with the 13B.
--
Perry Mick
Custom Composite Props
mick@bridgingworlds.com
http://www.ductedfan.com
I am willing to bet if you put an exit duct on it stright back, like you
tried with the water rad air outlet, it won't work as well.
BTW Sounds like the 82 is a two pass oil cooler while the 85 is a single
pass. Is that true? Or are they both two pass?
Paul Lamar
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