Tesla Model Y shares about 70% of its parts with the Model 3, but its heat pump and octovalve are not one of those components. Thus far, the Model Y is the only Tesla with a heat pump and Octovalve.
In one of his teardown videos, Sandy Munro explained that the Octovalve powered everything that needed to be cooled and heated. Tesla CEO Elon Musk spoke about the complexities of the heat pump and the eight-valve model Y in one of the episodes of the Third Row Tesla podcast, where he appeared as an unexpected guest. Musk explained that the Octovalve allowed the Model Y to do multiple things simultaneously, supporting the heat pump’s function. He commented that it was a smart valve design.
In the last episode of the analysis of Model Y, Munro examined Octovalve more deeply. At the same time, Jalopnik was also interested in a unique and complex system, so it turned to Munro’s president Cory Steuben to clarify some details.
Most modern cars have an air-to-refrigerant condenser that sits near the front of the cooling module, almost always ahead of the radiator. The condenser’s job is to cool refrigerant so that it can be used to chill various components — generally a vehicle’s cabin by sending the frigid refrigerant to an another heat exchanger in the dash (the evaporator) to pick up heat from air in the car’s interior.
In the case of the Tesla Model Y, instead of having an air-to-refrigerant heat exchanger (condenser) at the front of the car, there’s instead an air-to-glycol-based-coolant low temperature radiator out front. That radiator sends cold coolant to the “stack" -style condenser, which chills the gaseous refrigerant to bring it to a liquid state.
But this condenser isn’t just used to replicate what a typical car’s condenser does in an AC system. It also acts as a key part of a heat pump, which is a way to heat the cabin efficiently without relying entirely upon an electric heating element. A heat pump can be thought of as an AC system in reverse — strategically using the compressor and an expansion valve to heat refrigerant, and using that heated refrigerant to warm the cabin or possibly other components.
This system is very complex, even Musk does not know the way how to easily explain it. The main thing is that Tesla has all of this stuff tightly integrated into a small package, and controlled with complex valving.
The semi-solid forged aluminum refrigerant manifold is a fascinating contraption. With the help of the various thermal expansion valves, it apportions refrigerant between the different heat exchangers and other components in the AC system.
Source: Munro Live/YouTube
The back side is the more interesting one, because like the front, it contains coolant inlet/outlet ports, but it also has provisions for two electric water pumps and the “Octovalve.” That big rectangular shape molded into the nylon coolant manifold — the one containing the eight rectangular passages — is where the Octovalve sits.
Source: Munro Live/YouTube
The Octovalve contains a four-position electric stepper motor whose job it is to apportion liquid gycol-based coolant to various components in the car — whether it’s the motors, batteries, power electronics, or other systems that need thermal regulation.
Right next to the Octovalve are two water pumps that screw into that ornate liquid coolant manifold, and circulate the glycol-based fluid throughout the system. On the opposite side of the Octovalve, and up high, is the coolant bottle, which is visible under-hood, sitting right next to the 12-volt battery.
There’s obviously quite a complex control system that runs all the thermal expansion valves, that stepper motor in the Octovalve, the compressor, and other parts of this setup. Steuben from Munro told to Jalopnik the valves are hooked to a low-voltage harness, though there doesn’t appear to be a dedicated controller for this system. It’s likely integrated elsewhere.
Musk talked about the complexity of this cooling system:
"Applying the concept of a printed circuit board to cooling circuits allows you to achieve a very complex heat exchanger that you literally could not do with tubes."
Sandy Munro was also impressed by comparing it to transmission valve body or a part of a jet engine fuel system:
"This is more like what I would expect to see on a fuel system for jet engines ... or a transmission type of a design. These things ... are totally different than what we would normally see if we were looking at something designed by a normal OEM."
Featured image: Munro Live/YouTubeFollow @EvaFoxU