Engine Cooling

by Walter (Mike) Casey

Under Construction

June 3, 2008

Tufted cowling flying at 110 Knots.

March 17, 2008

The above photos show the heat exchanger connected to the oil and cooling lines.

February 19, 2008

The above photos are after cooling modifications.
The first flight test was February 19, 2008.
The flight lasted less than 10 minutes and was just a trip around the pattern.

Design Objectives:
1. Increase speed by reducing engine cooling drag.
2. Improve engine cooling.

Observations:
1. The new muffler is extremely quite. Great job Jan.
2. The coolant temperatures were extremely low 110°F.
3. The oil temperatures were extremely high 250°F.

Conclusions:
The high oil temperatures were not unexpected since I had removed the oil cooling radiator. I will now replace the radiator with a water heat exchanger. This is a device in which the engine coolant liquid is passed over pipes which carry the engine oil.The heat exchanger is shown in the photo below.

This first photo is the Eggenfellner 2.5L supercharged Subaru engine as it comes from the factory. I have 250 hours on this RV7A and have found that the top true airspeed is 155 Knots. I plan to increease this speed by decreasing the engine cooling drag. There are left and right radiators which blow directly onto the face of the engine block. At the bottom of this photo you can see an oil cooler.

First I installed this new red engine plate. The bell housing of the rear of the engine is bolted to this plate. Notice the engine plate extensions to the left and right side. These red extensions will allow the radiators to be moved from in front of the engine block.

Documents for ordering radiators and engine plates can be seen in the following pdf's.
The part number engraved on the new engine plate is MC-20061119.
Engine plate drawing
Radiator drawing

Below you can see the radiators. There will not be an oil cooler. If after testing I find that the oil temperatures are too high I will add a heat exchanger not an oil cooler.

We are installing a G3 reduction gear. There are two alignment pins which come with the reduction gear. We found that there is a possibility for the pins to push through the red engine plate and into the fly wheel. To prevent this we modified the pins as shown:

Below you can see the alignment tool used to align the red engine plate to the bell housing of the engine.

View of the Generation III reduction gear mounted to the engine plate. When alignment is proper, the reduction gear will slide on with almost no effort.

The below photo shows the air inlet ring. All air will be ducted.

The air will exit through gill slits on the sides.

The idea for gill slits came from Alex Bowman and his Europa XS powered by a watercooled Honda engine. See June 2006 SportAviation magazine for more details.

Here you can see the induction air inlet taking shape.

The cowling is starting to take shape by forming a thin layer poster board then applying a single layer of fiberglass.
Duct tape is then applied to the fiberglass. Bondo will then be applied to the duct tape.

Bondo has been applied to the duct tape to make a plug for the new cowling.

A release film is applied on top of the Bondo. The release film is actually clear 3" wide packaging tape.
Three layers of fiberglass are now laid on top of the release film. The fiberglass will then be drilled for clecos and the fiberglass removed.

Jeff of EK Composits removing the new fiberglass cowling.

Erik Woods of EK Composites.

Removing the plug.

Excess fiberglass from the original cowling is cut away. There is a 2" overlap between the old and new cowling. Flox is laid between the new and old cowling and clecoed in place.

Mike Casey on left. Jerry Ballard, who is making similar modifications to his H6, on right.

The plugs are made for the cooling air input.

Plug is made for cooling air side exit.

The finished cowl before painting.

This is an all in one tool I built for removing the pin from the Carbinge piano hinge that connects the bottom cowl to the upper cowl.