An aftercooler, also known as an intercooler, is a component found in turbocharged and supercharged engines, such as trucks. The aftercooler is responsible for cooling the compressed air that flows through the engine's intake system. The compressed air generated by the turbocharger or supercharger can become very hot, which can reduce its density and therefore its efficiency. The aftercooler cools this hot air before it enters the engine's combustion chamber, increasing its density and providing more power to the engine.