In the variable injection timing (VIT) pump used in MAN B&W engines, the governor output shaft is the controlling parameter. Two linkages are actuated by the regulating shaft of the governor.
The upper control linkage changes the injection timing by raising or lowering the plunger in relation to the cam. The lower linkage rotates the pump plunger and thus the helix in order to vary the pump output.
In the Sulzer variable injection timing system the governor output is connected to a suction valve and a spill valve.
The closing of the pump suction valve determines the beginning of injection. Operation of the spill valve will control the end of injection by releasing fuel pressure. No helix is therefore present on the pump plunger.
