Piezo Actuator

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The piezo actuator consists of a series of small disks. When the piezo actuator is electrically energized, it causes the disks to deform which results in an expansion. The expansion generates a longitudinal motion which pushes down against the valve piston. When the PCM supplied current is removed from the piezo crystals, they contract. When the crystals contract, they create voltage (current flow reverses). The PCM supplies current to the piezo stack and when the injector is deenergized the current is removed from the piezo stack and stored by the PCM to actuate the fuel injector in a companion cylinder. The piezo actuator returns to its non-energized state by fuel and spring pressure during engine operation, and by the spring pressure from the fuel injector valve return spring when the engine is shut down.