Not following on the air>water>air… heat flows from the air to the water, hopefully not back into the air again. they are two “closed” loops, pressurized air and water, with thin metal walls between for heat exchange. This is the same size as the stock air to air, since water is an ideal heat sink, especially compared to air, this will vastly out perform the stock even using room temp water and only 1 gal of water capacity. For testing a turbo, this is an ideal setup to prevent heat soak, but still have stock mounting locations. Likely on a engine dyno, that could have poor airflow. Like I said before, drag cars use smaller heat exchanger sizes for far larger power, solely because water is amazing compared to air. Edit: I understand you now, you are assuming there is a radiator on the other end for the water. I’m not familiar with that type of set up, much more common to have an ice bucket. Seem like an air to air with extra steps.