Variable injection timing (VIT)

Variable injection timing (VIT) is a mechanism on camshaft two-stroke engines that shifts the start of fuel injection with load by raising or lowering the fuel-pump plunger relative to its cam, advancing injection at part load to hold peak firing pressure near its rated value across the upper load range. Holding peak pressure high improves fuel consumption at part load. VIT is a mechanical rack-and-pinion or eccentric adjustment on the pump suction valve or barrel, set by the governor or a load signal. Electronically controlled engines such as the MAN ME and the Sulzer RT-flex achieve the same effect in software, setting timing per cylinder and per load with no separate VIT gear.