Misc Cooling and Efficiency Mods

I've been gathering small tips here and there from other builders in an attempt to sweeze a bit more effeciency and power from my engine. Most of it is small stuff, and I'll include them here when they don't fit in anywhere else.

Flight test data indicated the front cylinders were running significantly cooler (40-50 degrees) than the rear cylinders. EGTs follow suit with the CHTs, and the engine was running rougher than it could/should due to the uneven power output. To even out the cooling, air deflectors were fabricated to divert a portion of the incoming cooling air away from the front cylinders and to the rear cylinders.
The size of the air dams will need to be determined through trial and error. I started small and will adjust bigger or smaller until I ballance out the CHTs.
Once the ideal dimentions have been established, the air deflectors will be permanently attached to the bafles.
Several versions of the air deflectors were fabricated and tried, and the results were not as dramatic as I had hoped. As the deflectors got taller, they obscured more and more of the front cylinders from the cooling air. This caused the CHTs for the front cylinders to raise a bit (up to a maximum increase of 30 deg F), but after a point, very little additional effect was noted on the rear cylinder CHTs.
After crunching all the data, I settled on deflectors approximately " high, but with holes in them to ensure the cylinder still gets some cooling air on the front side. This seems to give me the best of both worlds (slightly lower rear CHTs, but only slightly higher front CHTs as well).
The exhaust system was ceramic coated by Performance Coatings Plus in Joplin, Missouri. This reportedly sends more heat out the tailpie and less into the engine compartment. To further enhanse this goal, the pipes were wrapped in fiberglass exhaust wrap. More heat out the tailpipe theoretically equates to more power, and should help reduce the temperature in the lower cowling, thereby improving cooling.
VW heads have a gap in the middle to allow cooling air to pass through the head. Small air dams were fabricated out of 0.025" aluminum and safety wired to the heads. They should cause the cooling air to be deflected into the surrounding cooling fins, and improve cooling, if only slightly. I haven't run tests accurate enough to determine if they are helping or not, but for now, I'll just leave them in place.

Misc Repairs

The oil cooler braided hoses were rubbing on the cowling and had nearly cut a hole right through.
The solution was to shorten the hoses slightly to prevent them rubbing the cowl and repair the hole with a fiberglass and epoxy patch.
I damaged the right wheel pant in a particularly nasty crosswind landing. The wind was really blowing, and the crosswind capability of the Sonex was definitely put to the test. The landing turned out OK, but the side load on the wheel flexed the tire enough to grab onto the inside of the wheel pant. The moveement of the pant hogged out the outside attachment screw hole until a gapping hole was left!
Again, additional fiberglass and epoxy repaired the damage. The nasty part will be repainting the wheel pant :-(


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Updated: 13 May 08