The turbocharger and supercharger are devices that force air into the cylinders creating a pressure that is greater than the atmospheric pressure in order to increase engine output. Generally, the engine output is determined by the amount of the air-fuel mixture, burned over a specified period of time, and becomes greater as the amount of the air-fuel mixture increases. That means in order to increase the engine output, either the engine displacement or engine speed must be increased. The problem is that as engine displacement increases, engine weight also increases and factors such as friction loss, vibration and noise of moving parts limit the increase of the engine speed. The super charger meets the opposing requirements of increasing engine output while keeping it compact and lightweight by supplying greater volumes of air and fuel without changing engine size. The devices are driven by two methodsThe turbocharger is driven by exhaust gas and the supercharger is driven by the engine. Toyota adopted the turbocharger in 1980, and the supercharger in 1985 in Japan. Presently in 2002, only the turbocharger is used in overseas models.