An air to air intercooler used in a turbocharged or supercharged application is used to extract heat from the compressed air that travels through its network of tubes and fins. There are two types of intercoolers, air to air and air to water.
The intercooler cools the air that has been compressed by the turbocharger or supercharger, increasing the engine's supply of denser air. When the turbocharger compresses the air, it becomes very hot and starts losing its oxygen content. By the intercooler cooling the air, a cooler and oxygen-enriched air is provided to the engine for an improved combustion by allowing more fuel to be burned. An intercooler also increases reliability of the engine by providing a constant temperature of air that allows the air fuel mixture to stay at a safe level.
An air to water intercooler uses water that is pumped through an intercooler to extract the heat from the air that is passing through the fins and tubes. Air to water intercoolers tend to be smaller than the air to air intercoolers, which makes them more suitable for someone with space issues. The downside for the air to water system is the complexity, the added weight and the added cost of the additional parts.