Hi Guys,
It looks like I might have solved my cooling problems!
What I did:
I took the oil cooler completely out of the duct. The cooling duct now
only supplies air to the water radiator.
The oil cooler is now mounted on the starboard footwell. It is fed with
cold air via an internal simple wedge shaped diffuser, connected to a 2
inch scat-tube that runs to the front of the airplane, to a 2 inch hole.
(2 inch is pretty minimalistic for this huge oil cooler but a 2 inch
scat tube is what I found in my airplane surplus box.) The warm air
exiting the oil cooler is simply dumped inside the cowling (and can
still absorb some more heat there).
I closed off the front round 3" air inlets completely to reduce pressure
inside the cowl. This to further promote air flow through the more
usefull air inlets. (For cylinder cooling I have two small naca inlets
in the top cowling aimed at the cylinders).
I built an exhaust augmenter to suck the warm air out of the cowling.
So, this evening we ground tested the system.
First thing we noticed was that it took an unusual long time to warm up
the oil. Also the water temp was lagging quite a bit.
After the engine was warmed up sufficiently I revved the engine up to
4200 rpm. In previous tests I used this setting to measure the time
until something reached red line (usually water and oil touched the red
line at about the same moment).
Well, this time I couldn't reach any red line with this power setting!
Temperatures just stabilized in the middle of the green zone. Unbelievable.
So, after some time I decided to just give it all. Full power.
It took two minutes before finally the oil reached the caution zone. The
water was still in the green zone at that time.
I let the RPM drop, and the oil temperature came down again.
So, at least the ground cooling problems seem to be over. (Ok, I should
test again with really hot weather, but it looks like that that is not
going to be a problem.) This is with a minimal amount of air stolen from
the front of the airplane: Two naca ducts for cylinder cooling, one 2
inch hole for the oil cooler, and the trimmed down cooling duct opening
for the water cooler. Far less than the Europa normally has, so it
should be a relatively very low drag setup.
Whose idea was it to have the two radiators behind each other? I think
this was a grave design error.
If weather cooperates, we can tomorrow do some flight testing. I will
let you know.
Frans
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