Ford 6.4L Power Stroke, Manual

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48
98
Fuel ManageMent SySteM
99
Main Injection Step 1
• Fuel under pressure from the rail (7) reaches the
control piston chamber (2) and the high pressure
chamber (3) of the nozzle needle (5).
• The bore hole to the fuel return line is closed
via the valve mushroom (4), which is held
closed by a spring and high pressure fuel.
• The surface area of the control piston is much
larger than the surface area of the nozzle
needle in the high pressure chamber.
• The force (F1) exerted by the control piston due to its
larger surface area along with the force of the needle
control spring overcomes the force (F2) exerted by the
smaller surface area of the nozzle needle in the high
pressure chamber which holds the nozzle needle closed.
Main Injection Step 2
• When the piezo actuator (1) is commanded on,
the actuator is energized (which causes the piezo
discs to deform and create a downward force)
and pushes the valve piston (8) downward.
• The downward force of the valve piston pushes
the valve mushroom (4) and spring down which
opens up a bore hole that connects the high
pressure fuel to the fuel return line (6).
• When this happens it allows a small amount of high
pressure fuel to enter the fuel return line (6) effectively
dropping the pressure in the control piston chamber (2).
• This pressure drop is enough for the force (F2x) on
the nozzle needle (5) in the high pressure chamber to
overcome the force (F1x) in the control piston chamber (2).
• This allows the nozzle needle (5) to move upward
uncovering the six spray holes and allowing high pressure
fuel to atomize and enter the combustion chamber.
7
2
3
5
4
F1
F2
F1x
F2x
6
1
2
4
5
8
6
1