Hi Al;
Just
a couple of questions to clarify a couple of things… Are you still using a separate
air/oil cooler as well, or did you convert the oil cooler to another coolant
rad? I’ve considered adding a small cooler like yours in addition to my 2 Evap
cores (coolant) and Mazda oil cooler, just to “balance” out the heat. I always
found that the oil temps lagged far behind the coolant temps (in both heating
and cooling), so I felt it may add some value to making temps more stable. It
wasn’t a big problem but just something I thought could use some improving. But
then I had a kid and got so darn busy with other things that I don’t have time
to fly anymore so it’s the least of my problems…. But I’m working on getting
back there… soon, I hope!
It
seems to have worked very well for you. You’re using a turbo on that 20B as
well aren’t you? Because as I’m sure you know, the turbo will add a significant
amount of heat.
I’m
always surprised that those who have custom rads made, don’t incorporate an oil
cooling loop through an end tank, just like a transmission cooler but with a
little more capacity.
Todd
Bartrim
Turbo 13B RV9
-----Original
Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]On Behalf
Of Al Gietzen
Sent: Wednesday, April 23, 2008
10:23 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Cooling sytem
changes- Velocity 20B
Brief
background: the oil temp was getting too high on extended climb - coolant temp
was OK, but I knew the wing-root radiator was not doing much due to low air
flow.
Mods:
I installed an oil/water cooler in the return line from the in-cowl radiator, I
re-did the scoop and the shape of the diffuser to the wing-root rad, and installed
an in-line 170F thermostat in the feed to that rad. A number of other small
fixes; and converted from the OMP injecting pan oil to using pre-mix. I
put Mobile 1 15-50 in the pan.
First
test, a ground run to check everything out find leaks, purge air etc.
After that some power running on the ground. The oil temp was no longer
the limiting factor, and stayed closer to coolant temp as expected. What
wasn’t expected is that overall cooling on the ground was significantly better.
The only explanation could be that the new scoop and diffuser are so much
better, just sitting face into the 10-12 kt breeze helped the cooling.
First
test flight: OAT 68. Climbed to 3000’ and orbit the field. Temps stayed
well below limits in climb, and at cruise conditions the oil was 165 and the
coolant 140. Too cool? Not even up the 170 temp of the #2 rad.
I had drilled some small holes in the thermostat to give at least some
flow, apparently even that was too much.
Second
flight: Went east over the hills to the dessert where the temp a Borrego
Springs was 85. I did a touch and go; then climbed at 1500-2000 fpm from
800’ up to 6000’. Oil stayed below 210; coolant about 195. Cruising
back the coolant temp again dropped to about 145.
Is
it not a good idea to run the coolant that low? I can change out the
thermostat and not drill holes in it.
The
oil cooler I installed is a MoCal Laminova. These had also been sold by
Aeroquip, but not any more. Not very high capacity, but very compact and fits
where I wanted to put it (on the firewall, below the filters, where my HP3001
filters no longer fitJ). (photos 1 & 2) I had wanted to use the Setrab
TOC300, but they are not currently making those.
On
the re-do of the scoop and diffuser, I made a mold and formed a unit the would
fit inside of the previous cutout in the wing. It is a curved adaptation
of the K&W coordinates, and includes provision for bleeding a ¼” boundary
layer to the top edge of the core. (photos 3 & 4). My previous
flow measurements had indicated the BL was about ¼”. Whatever; it seems
to be working very well. Perhaps had I done that same treatment to the
oil cooler scoop and diffuser I could have skipped the complex task of
installing the oil/water cooler. Nah, don’t even go there!
BTW;
Tracy. I have not noticed any increase in power with the pre-mix.
But then I’m not using any Marvel Mystery oil. It must be those high
power additives in the MMO I mentioned that make the differenceJ
Al