Abstract: A speed governor for engine includes a variation removing circuit responsive to an engine rotational speed signal indicative of the rotational speed of a diesel engine to remove a periodical variation component of the signal due to the pulsation of the output torque which the diesel engine generates, from the signal. The period of the variation to be removed by the variation removing circuit changes with the change of the rotational speed of the engine. The variation removing circuit may be formed of a sample-and-hold circuit or a variable characteristic filter of which the suppression frequency is variable.

Abstract: A fuel injection timing control system of an internal combustion engine of a compression ignition type including a fuel injection pump driven by a cam connected to the engine, and a valve operative to return a part of the fuel delivered by the fuel injection pump to fuel source. The advance angle of the cam is set beforehand at a value bigger than those assumed in the range for normal operation, and the real fuel injection timing is modified by actuating the valve according to operating conditions of the engine.