As a vehicle travels, ambient air enters through the air intake and passes through the intercooler's internal chambers and cooling fins. These fins transfer heat from the air passing through them to the exterior of the intercooler, lowering the internal temperature. This heat--removed from the intercooler as outside air--passes through the cooling fins, creating a cooler internal air temperature that's denser and provides more oxygen to increase combustion. The cool air is then routed to the turbocharger.
Air-to-air intercoolers cool air by transferring heat with their cooling fins. This requires the intercooler to be mounted in an area of the vehicle that maintains a high flow of passing air. The high-pressure zone toward the front of the vehicle provides an optimal flow of cooling air.
An air-to-liquid intercooler operates in a similar way to an air-cooled intercooler. Outside ambient air enters through the air intake and passes into the intercooler, transferring heat through a jacket of liquid coolant held between the external and internal walls of the intercooler. Water is typically used, because it can transfer more energy while heating up substantially less. The cooled air is then transferred to the turbocharger while the heated liquid is cooled by a separate radiator.
