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Ford Kuga
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Fuel Charging and Controls - Turbocharger- 2.5L Duratec (147kW/200PS) - VI5 » Turbocharger (System Operation and Component Description)
System Operation

Turbocharger(s)

The TC consists of a turbine and a compressor.

The turbine is driven by the exhaust gas flow. A common shaft drives the compressor and this then compresses the intake air.

Turbocharger boost pressure control

Turbocharger boost pressure control

Item Description
1 Atmospheric pressure
2 Turbocharger boost pressure
3 Wastegate control valve
4 Pilot pressure

The size of the TC is designed to produce a charge effect even at medium engine speeds and lower exhaust gas flows. This means that, when the engine speed is high and there is a large amount of exhaust gas, either the boost pressure of the TC will become too high or its speed will be too high. The TC must therefore be regulated. The best regulation is achieved by an electronically controlled wastegate control valve. The wastegate control valve controls the pressure on the membrane in the boost pressure regulator.

The wastegate control valve is actuated by the PCM with a PWM signal according to a map. The boost pressure is applied to the wastegate control valve via the pressure line from the compressor.

This pressure is passed to the boost pressure regulator via the wastegate control valve. This opens the bypass valve using a linkage. This channels a portion of the exhaust gases around the turbine. If the wastegate control valve is actuated by the PCM, a bypass is opened in the wastegate control valve. This causes the pressure which can act on the membrane in the boost pressure regulator to be reduced. This occurs until the boost pressure has reached a set value. By actuation with a PWM signal, it is also possible to partially open or close the wastegate control valve.

This results in a constant boost pressure and therefore high torque over a wide range of engine speeds.

Because the PCM calculates the boost pressure using the signal from the boost pressure sensor and the IAT (intake air temperature) sensor, the atmospheric pressure and the temperature are automatically compensated for. Because of this compensation, the engine power is not noticeably affected by variations in atmospheric temperature or pressure.

Recirculated air valve

Recirculated air valve

Item Description
1 Recirculated air valve
2 Vacuum hose to intake manifold
3 Air ingress
4 Air discharge

If the throttle valve is closed quickly, the moving air column hits the throttle valve. The air column is reversed, flows back onto the rotating impeller of the TC and powerfully decelerates it. A recirculated air valve is installed to prevent this deceleration of the impeller and thus allow the TC to respond faster. The recirculated air valve is controlled via a vacuum line which is connected to the intake manifold. When the throttle valve is suddenly closed, a high vacuum occurs in the intake manifold. This opens the recirculated air valve and the compressed air is returned to a point before the compressor. This causes the speed of the turbocharger to drop less rapidly and the boost pressure can build up more rapidly when the accelerator pedal is pressed again.

    More about «Turbocharger (System Operation and Component Description)»:

    System Diagram

    System Operation

    Component Description

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