An intercooler is a device used on turbocharged and supercharged internal combustion engines to improve the volumetric efficiency and increase the amount of charge in the engine, thereby increasing power. The inter in the name refers to its location compared to the compressors; the coolers were typically installed between multiple stages of supercharging in aircraft engines. Modern automobile designs are technically aftercoolers because they appear at the very end of the chain, but this name is no longer used.
Turbochargers and superchargers compress incoming air, causing it to become heated (see the universal gas equation). Since hot air is less dense than cooler air, the total charge delivered to the cylinders is less than it could be. By cooling the charge after compression, even more charge can be delivered, increasing power.
An intercooler is essentially a radiator tuned for high flow rates and the increasing density of the charge as it cools. Most designs use ambient air for cooling, flowing through the radiator core, and often collocated with other radiators for oil or cooling fluid. An alternate design, often referred to as a charge cooler, uses water to cool the charge, then cools the water in a separate radiator. While heavier and more complex, charge coolers can often make arranging the engine much simpler.
Vortech water cooled aftercooler kit
Intercoolers need to be mounted so as to maximize air flow and promote efficient cooling. Cars such as Saab or Mitsubishi Lancer Evolution use front-mounted intercoolers mounted vertically near the front bumper, in line with the car's radiator. In contrast, cars such as the Subaru Impreza WRX mount the intercooler horizontally on top of the engine and use a hood scoop to force air over the intercooler. Some World Rally Championship cars use a reverse-induction setup, where air from ducts in the front bumper is forced up over a horizontally-mounted intercooler and then vented through ducts in the top of the hood.