As an inspector I come across quite a few liquid cooled engines in home-built airplanes.

If your engine overheats on the first flight it may put you or the pilot in a possible dangerous situation. I recommend tying the airplane to a tree/building and operating the engine at full throttle for 10 minutes, then throttling back to parcel power setting, 5 minutes or so and see if you are able to maintain your desired coolant temperature. If you loose coolant on this test the aircraft is not ready to go around the circuit, and remember you or the pilot may not be able to land on the first approach, one has to plan to go around but if the engine temp is out of limits this may turn into a bad experience. Note of caution the pilot must be at the controls (inside of airplane) to carry on such a test.

It is best to look what others have done to their projects, but make sure they have been successful, ask how far have they been on a trip and what time year (outside ambient temp.).

Gauges, a coolant temperature is a shall, it should be tested it in a pot of boiling water, and if water boils at 212 the gauge should read same. A good tool to have on-board is a coolant pressure gauge, 0 to 15" psi or even a turbo mechanical guage sold for manifold pressure monitoring. This will buy you time if a coolant leak takes place while you are cruising along at a given speed and altitude. I recall on a trip to Oshkosh loosing my EGT prove readings (used to monitor mixture) I was able to lean the engine at attitude using my coolant pressure, lean out; temp goes up pressure increases in the cooling system, add more fuel heat dissipation requirement decrease coolant pressure goes down.

On the Nessa II C-GJIV I used an Evaporator core from 1987 full size Chevrolet at first this was under the firewall/floor behind the bottom of the cowling, the evap was just out in the breeze, no ducting. On a hot day above 80°f. this was very marginal with the 3 cyl Geo, but the engine at that time was operated by the factory engine computer (fuel injection), the EGT was above 1500° f. on climb out, too lean, the O2 sensor was not looked at above 4,000 rpm with the Canadian emissions software it just operated in a fixed fuel setting.

When I install the four cylinder 1300, a Rabbit diesel rad was installed on a slant with a shroud under the belly. This rad double as the cabin heater by installing a flapper door (on the belly of the fuselage) two 2.5" holes make the occupant very happy on a cold day. I should mention that the shroud ends up with a cowl exit door that the pilot operates.

I have never used an engine coolant thermostat it was one those things "what I not installed", "will not fail", a 5/16" orifice hole (restrictor) became the control factor (exit port), this allows for winter operation 185° f. and summer of max 230°f on extended climb out.

On Rabbit rad the rad hose necks are about 1.125" in dia. I used about a 3" section of rad hose to connect to a home made reducer (copper fitting from the local hardware store ended up soldered) the engine out coolant (upper rad hose) hose is 5/8" id heater hose. The lower rad hose is3/4" id heater hose. Smaller hoses = less coolant = less weight.

two GM evap cores, very efficient cooling expansion/filling tank feeding water pump

Original installation of a Rabbit rad forward of firewall with ram air from the Naca inlet forward of windshield was not effective.

I took two evaporator cores, used ones that leaked freon at 180 psi or so from GM "N" platform, part # 52473912 or AC Delco 15-6880. Get to know the Tech that does air-condition at a GM Dealer, they change many cores during hot spells, due to regulation in most places now, a small detected leak must be corrected. In some cases the leak would take all summer to leak out, this type of leak will not leak liquids, the replaced cores are being scrapped get the idea.

The Core is about 7" x 13" x 2.875" with an effective cooling area of 6.9" x 10" x 2.875" about 198 cu. In. weight of 3.6 lb. One end is 5/8" tube, the other is 1/2"aluminum tube. I cut off the ˝" and drilled the same hole to ž", cleaned out the chips and welded on the ž" aluminum tube using my Tig; it will not melt the factory bonding of the joints. One may also use the Aluminum brazing rods (as you see at Oshkosh welding pop cans with propane torch) but it requires a technique that must be mastered, it is easy to end up with a porous weld with this brazing rod.

Brackets may be also welded to the bottom and top .070" aluminum plates that support the assembly, in my case using 1/8 drill with a built-in depth stop (not to drill core and create a leak) I mounted my support brackets and shrouds using 1/8 pop rivets.

At this point the 2 cores exceed my cooling requirements, I am having problems to achieve pressurizing readings on my cooling pressure gauge, I may try installing a thermostat to control the upper core. Total volume of coolant liquid < 5 liters.

a) Install aircraft type heater valve at bottom end of firewall and connect to a small area of the bottom core using a 2" scat hose, this will become a cabin heater when not needed (heat) the hot air just exist out on to the bottom of cowling exit area.

b) Install an oil cooler, I notice that my oil pressure drops about 7 psi after flying for 1.5 hours, I have made an adapter that will fit between the oil filter and the block, this unit will route the oil to an oil cooler that receives cold air from the Naca inlet forward of windshield, this inlet will have a cockpit controlled inlet valve. The oil adapter will have places to insert temp proves to learn what the oil temps in and out are.

welded new 3/4" tube to be exit of core cabin air heat box, valve 3.2"x 3.2" weight < 4 oz

Oil cooler adapter duplicating oil filter side this side is like the block the oil filter will spin on

jim@nessaaircraft.net

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