To control the injection valves, the new Common-Rail injectors use a rapid-action actuator made of piezo crystals to control the injection valve. The piezo crystals expand within an electrical field. The electronically controlled piezo actuator switches five times as fast as a solenoid. The movement of the piezo package is transmitted non-mechanically - and therefore entirely without friction - to the rapidly switching nozzle needle. This doubles the injector's switching speed, allowing a more precise measurement of the amount of fuel injected and thus leading to a reduction in harmful combustion products.