A heat exchanger that cools the air leaving a turbocharger or supercharger before entering the engine, increasing density and power.
Intercooler is a heat exchanger placed between a forced induction system (turbo or supercharger) and the engine intake. The compression process heats the intake air; cooler air is denser and contains more oxygen molecules per volume, allowing the engine to make more power. The intercooler reduces intake air temperature, increasing density and improving combustion efficiency.
Two main types exist. Air-to-air intercoolers use ambient airflow over a finned heat exchanger to cool the intake charge. They are simpler, lighter, and more reliable. Most factory turbo applications use air-to-air. Air-to-water intercoolers use a coolant loop with its own radiator, allowing the heat exchanger to be packaged anywhere in the car. They are more efficient at low speeds (no airflow needed for cooling) but more complex.
Aftermarket intercooler upgrades are common on turbocharged cars. Larger intercooler cores reduce charge temperatures more effectively, improve consistency under sustained boost, and allow safer running at higher boost levels. The trade-off is added piping length (which can slightly increase turbo lag) and front-end weight. Popular intercooler brands include Mishimoto, AEM, Greddy, Spearco, and Garrett.