Abstract: An engine management system for 4-cycle engines includes a processing means and utilizes various inputs from sensors operatively connected to the engine for the purpose of providing the correct fuel/air ratio or spark ignition angle for the engine in a manner whereby the transient response is fast. The engine management system utilizes the rotational speed information that is obtained from a magneto or speed sensor to determine the speed of each engine revolution. The system effectively solves many of the fuel/air ratio problems that are caused by load transients occurring on the engine. By comparing such high pass filtered speeds of selected revolutions, the system is able to determine the inferred engine intake air flow. By using measured system rotational inertia compensation factors for the engine together with the inferred intake air flow, the system can accurately determine the amount of fuel to be fed to the engine for proper operation.