This fuel injection system was derived from the original Bosch® Motronic Engine Management System that was first used on early nineties VW's. Fuel metering is derived from engine speed as well as load. The Engine Management System meters this fuel by sequentially firing the fuel injectors at a varying rate. Fuel volume is controlled by the duration of time the injector is left on. This "Injector Dwell Time" is usually measured in milliseconds of time.