Almost forgot one of my experimental systems. I am using the Vintage Air 66005-VUZ-A Gen II Mini System for my A/C and heating. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1. The problem with this system, as you may have read elsewhere, is that it comes with a valve that is either open or closed. The Subaru coolant system must continue to run a loop to the coil that is inside the car. So typically others have replaced the 2 way valve with a 3 way or run tubing configurations to make this work.

I have a theory that the loop tubing that FFR has you put in the top engine coolant manifold to the smaller suction on the water pump causes a drop in coolant efficiency. If you own a subaru, you know that hot air is typically always coming out the side vents. This is because the coil inside the car is continuously dispersing heat. In the FFR, there is nothing to do this.

To fix this issue, in my car, the smallest diameter tubing for coolant is right off the engine. I used the supplied FFR corrugated stainless tubes right off the engine down to hose fittings, then into aluminum 90 degree bends that I welded to the side tubes factory five provides. From there to the radiator, the inside diameter is larger. So I welded barb fittings into these 90 degree bends back at the engine. Rather than installing FFR's U bend tubing for the coolant, I route the manifold connection down to the new barb fitting in the 90 degree bend going to the front radiator on the right side of the car. The suction of the water pump is connected to a barb fitting in the return 90 degree on the left side of the car. This means that even before the thermostat opens, there is a continuous slow flow of coolant up to the radiator. It may take my car longer to warm up now, but I am hopeful that my engine is getting as much cooling as possible.

For the vintage air HVAC system, I am relying solely on the small pressure differential across the radiator to pull a little coolant through the coil. I welded another barb fitting in the right side coolant line just below the HVAC system and installed another barb fitting in the left side coolant line running back to the engine. The Vintage Air valve is installed in this circuit to close and open as needed. If I can't get enough flow, then I will buy a little pump and replace the valve with a pump that the Vintage air system will turn off and on as needed.

Please don't judge me on these welds. I was in a hurry and did not properly clean the aluminum the first time.