Turbocharger - 1.6L EcoBoost

Description and Operation

General information

This is an exhaust gas turbocharger with fixed turbine geometry and a turbocharger bypass valve.

The turbocharger is cooled with coolant from the engine coolant circuit.

At the turbocharger are
• the boost pressure control solenoid valve,
• the recirculated air valve and
• the recirculated air valve solenoid.

Boost pressure control

The boost pressure is controlled by the boost pressure control solenoid valve. It controls the opening cross-section of the turbocharger bypass valve via the turbocharger pressure control.

The PCM (powertrain control module) receives information on the currently available boost pressure from the MAPT (manifold absolute pressure and temperature) sensor. This is therefore a closed loop.

The boost pressure for the respective operating states is individually set via the solenoid valve.

Boost pressure from the compressor wheel is applied at the solenoid valve. The solenoid valve is actuated by the PCM by means of PWM(pulse width modulation).

The pressure acting on the turbocharger vacuum control is therefore dependent on
• the applied boost pressure and
• the duty cycle of the PWM signal.

The following guidelines apply for actuation of the solenoid valve:
• duty cycle about 80 %:
  -

  turbocharger bypass valve fully closed
• duty cycle about 20 %:
  -

  turbocharger bypass valve fully open

Recirculated air valve

Sudden closing of the throttle plate causes backpressure in the intake tract between the throttle plate and the turbocharger compressor wheel. The deceleration of the compressor wheel has the result that, when it accelerates again, only a low boost pressure is available. This leads to a loss of power until the turbocharger has again reached its optimum speed. This behavior is generally called turbo lag.

The recirculated air valve prevents backpressure in the event of sudden closure of the throttle plate.

If the throttle plate suddenly closes, the recirculated air valve solenoid actuates the recirculated air valve with vacuum.

The boost pressure is routed to the intake side of the compressor via the now open bypass on the recirculated air valve. The turbocharger speed is therefore maintained.

Controlling the recirculated air valve

The recirculated air valve is controlled by the recirculated air valve solenoid.

The PCM receives information on the currently available intake manifold pressure from the MAP (manifold absolute pressure) sensor. This is therefore a closed loop.

The recirculated air valve solenoid is supplied with vacuum from the intake manifold and also from the vacuum pump. Because of this, the recirculated air valve can be controlled independently of the pressure in the intake manifold.

The vacuum is controlled by signals from the PCM to the solenoid and thus the recirculated air valve is opened or closed.

The solenoid valve allows the PCM to determine the opening and closing time of the recirculated air valve. Earlier opening of the recirculated air valve avoids backpressure through sudden closing of the throttle plate. This minimizes noise emissions and increases the life of the turbocharger.