Duration is related to fuel delivery -- the more fuel to be delivered,
the farther the sleeve is rotated, and the farther the plunger has to
rise before the vent slot in the plunger opens to the end of delivery
(spiral) groove in the sleeve. VERY slick, as this longer duration
injection also produces the lovely torque of our diesels.
MB uses a centrifugal advance mechanism to move the start of injection
earlier as the engine speeds up -- some diesel locomotive engines use
unit injectors (driven by a cam for each cylinder instead of in a
separate pump) that actually advance the injection timing with
increasing fuel -- the fill slot is helical rather than the vent slot,
so more fuel injected means earlier injection.
Peter
