3315480 - Introduction - ENGINE TURBOCHARGING SYSTEM

MANAGEMENT OF THE TURBOCHARGER PRESSURE

The supercharging pressure is controlled by the injection control unit which operates a Pierburg solenoid valve connected, in turn, to the wastegate valve actuator.

Pierburg solenoid valve de-energized

Ducts A and B are in contact and the supply pressure arriving at duct B acts on the wastegate valve regulating the supercharing pressure.

Pierburg solenoid valve energized

The supercharging pressure is controlled by the injection control unit which operates a Pierburg solenoid valve connected, in turn, to the wastegate valve actuator.Ducts C and A are in contact, whilst duct B is closed.In this way the pressure supplied by the turbocharger, rather than acting completely on the wastegate valve, is partly discharged into the inlet manifold with a consequent increase in the engine supercharging.The solenoid valve is activated by the injection/ignition control unit in Duty-Cycle at a fixed frequency with variable opening times for duct C.

The Duty-Cycle varies according to the sample curves stored in the control unit memory which take the following into account:

• pressure in the air chamber
• engine rpm
• position of the butterfly valve

In this way the supercharing pressure can be continuously modulated, making the following possible:

• high torque in a wide engine speed range
• gradual, even power
• guaranteed constant engine performance over a period of time.

Warning: The control unit immediately interrupts the injection impulses if the supercharging pressure exceeds around 1.5 bar and restores it when the pressure goes below the above mentioned figure.