Engine Cooling Optimization

Feb 2006 - While the prop is out for re-pitching, I elected to make some changes to the engine area for cooling. The first modification was to relocate the oil cooler. This is my third location for the cooler in an attempt to get temps down during extended climbs on hot Arizona summer days. The last location under the wing in the cowl didn't do much better than the top of the firewall location shown in the plans. I'm not ashamed to admit that the new location is not my original design. It is borrowed heavily from James Redmon's Berkut oil cooler location and mounting. The cooler is located aft of the oil sump in the lower cowl area.

I started by fabricating some cardboard templates for the mounting brackets, test fitting them until I was happy. I then made permanent .039" 6061-T6 aluminum brackets based on the templates. After getting the brackets just right I installed new fittings in the oil cooler and re-routed my cooling hoses to the new location. Luckily, since this was my third attempt, I had additional length hoses that I could reuse without having to fabricate new ones.

Here's the final setup with hoses attached also showing the new fuel divider.

After test fitting the cooler with the new brackets I was ready to fabricate an exit duct for the air. I made a mockup out of foam and carved it to the shape I was looking for. From the aft end of the cooler to the aft engine baffle where the duct would exit was approximately 8 inches. The duct is mostly rectangular with the edges rounded for easier fabrication. After getting the shape to what I thought I needed I covered the foam with duct tape and mounted it to the oil cooler that was also covered in duct tape for release. I then layed up 4 plies of BID over the foam and cooler flanges. After it cured I removed the foam, trimmed the edges and drilled holes into the flanges for attaching it to the cooler. I then mounted it to the engine to see how it all looked.

My original intent was to have the entire duct exit inside the lower cowl area through the aft engine baffling. When I got to looking at it though, it was clear that I wouldn't have enough area in the baffling without severely restricting the exit area. So I made the decision to have the exit penetrate through the lower cowl. After making a number of templates and "eye-balling" the effect, I cut the cowl. Man, I hate cutting up something that's perfectly good! Especially since I just finished repainting it less that 6 months ago. Once the cutter made the first bite, I didn't look back however.

The lower part of the cooler duct exits below the engine baffle while the top third exits through the baffle. I needed to close off this area inside the cowl so that it wouldn't just exit inside the aft cowl. I built up a foam plug again to mimic the shape of the top of the duct as it continues past the aft baffle and through the cowl and covered it with duct tape. I then layed up 4 plies of BID overlapping the inside of the lower cowl and onto the aft baffle (also covered with tape for release).

The last steps to be done are to make the final trim cuts of the duct, add some flexible engine baffle material to the duct to seal it against the lower cowl, and fill and paint the ducts and cowl. I should have this completed by the end of February.

Last Updated on March 18, 2006