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