N194TC Cooling Mods

N194TC Cooling Modifications

To deal with high temperatures during the summer in Arizona, I had to make several improvements. It was definitely a lot of work, and it took a bit of time to do everything, but it was worth it. Temperatures now in cruise flight are just above the thermostat temp, and I will only get over 200 deg F when running hard for takeoff.

First and foremost, was increasing airflow through the cowl. The two major changes here were the addition of louvered vents, and a bottom cowl flap that could be adjusted on the ground as needed to let more air through.

The second major change was to stop using NPG+ propylene glycol and go back to using 50/50 antifreeze and water. I did add a coolant pressure sensor to the system, which is connected to my Grand Rapids EIS engine monitor. It typically reports around 8 psi with the antifreeze mix.

The third major change was one of opportunity. Around the time I was doing the dual mass flywheel upgrade, I acquired larger radiators from someone that was parting out their H6. The radiator swap itself wasn't too bad but there were a lot of details that had to be fixed up.

The new radiators came with a fiberglass shroud that had to be mated to the cowling. I opened up the cowl inlets and used fiberglass cloth to join the cowl and shroud together to keep the smooth lines of the inlet. Then I used a Dremel tool to seperate the shroud and the cowl. This made a nice small and clean gap that flows nicely along the curve of the inlet.

Next, with the loss of the airbox on the passenger side H4 radiator, I had to make a new engine air inlet. I used a K&N model RU-5176 filter and some PVC pipe fittings to mate up to the SCAT tubing going to the engine intake. The tube runs straight down the back of the engine and the filter is clamped to the engine mount so that it doesn't move.

Finally, for reasons I can't remember, the H4 pilot side radiator had the original OEM Subaru coolant temperature probe in it, and I couldn't replace it. Using a generic coolant probe, I added a wire and spliced it into the harness. I had to add a resistor to bring the reading into the same range as the OEM sensor. Unfortunately I don't have the value of that resistor handy. You can see the original OEM connector zip tied to the wiring harness, and the generic coolant temp sensor with a 1/4" female blade connector on the pilot side radiator in the picture below.