Charging, function

P09.00-2116-06

1 Rail pressure, signal

2 Boost pressure, signal

3 Coolant temperature, signal

4 Charge air temperature, signal

5 Temperature upstream of turbocharger, signal

6 Pressure downstream of air filter, signal

7 Exhaust back pressure, signal

8 Crankshaft speed, signal

9 Fuel injectors, actuation

10 Boost pressure positioner, actuation

B4/6 Rail pressure sensor

B5/1 Charge pressure sensor

B11/4 Coolant temperature sensor

B17/8 Charge air temperature sensor

B19/11 Temperature sensor upstream of turbocharger

B28/5 Pressure sensor downstream of air filter

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B60 Exhaust back pressure sensor

B70 Crankshaft Hall sensor

N3/9 CDI control unit

Y76 Fuel injectors

Y77/1 Charge pressure positioner

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Function requirements, general

 Circuit 87M ON (engine control ON)

 Engine running

Charging, general

The cylinder charging efficiency is improved as a result of charging. As a result, the engine torque and power output are boosted.

When charging, the flow energy of the exhaust gases is used to drive the turbocharger.

The turbocharger suctions in fresh air through the air filter on the compressor inlet and feeds it through the compressor outlet into the charge air pipe upstream of the charge air cooler.

The high speed of the compressor impeller and the resultant high volume flow compresses the air in the charge air pipe.

Compression heats the charge air, which now flows through the charge air pipe to the charge air cooler. This cools off the charge air and feeds it through the charge air pipe to the charge air manifold.

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Turbocharging is regulated by the boost pressure control.

The boost pressure is regulated by the CDI control unit, depending on the following signals:

- Boost pressure measured by boost pressure sensor

- Coolant temperature measured by coolant temperature sensor

- Charge air temperature sensed by charge air temperature sensor

- Boost pressure downstream of air filter measured by pressure sensor downstream of air filter

- Air temperature upstream of turbocharger measured by temperature sensor upstream of turbocharger

- Injection quantity determined via the injection time of fuel injectors and the fuel pressure in the rail.

- Fuel pressure measured by rail pressure sensor

- Exhaust back pressure in exhaust system measured by exhaust back pressure sensor

- Engine speed measured by crankshaft Hall sensor

- Ambient air pressure measured by atmospheric pressure sensor

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Function sequence for forced induction

After evaluating the input signals, the CDI control unit actuates, based on the charge pressure characteristic map, the boost pressure regulator by means of a pulse width modulated signal (PWM signal). The position of the guide vanes in the turbocharger are altered via the control linkage of the boost pressure regulator. The adjustable guide vanes modify the flow cross-section through which the exhaust gas flows to the turbine. The guide vanes thus match the gas pressure present at the turbine to the required boost pressure. The turbocharger speed is used to determine the quantity of compress air and thus the boost pressure.

The boost pressure is monitored continuously by the boost pressure sensor.

The CDI control unit reads in the signals from the boost pressure sensor directly.

The exhaust temperature is monitored by the temperature sensor upstream of the turbocharger and the exhaust back pressure by the exhaust back pressure sensor for protection against overloading the turbocharger thermally and mechanically.

The CDI control unit reads in the signals from the temperature sensor upstream of the turbo charger and from the exhaust back pressure sensor directly.

The boost pressure is reduced if there is any risk of thermal or mechanical overload.