Input factors for injection control

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Calculating the engine speed and the crankshaft angle

The engine speed and the crankshaft angle are taken at the flywheel (1). There are 58 bores (2) on the circumference of the flywheel (1) for this purpose. These are located at a distance of 6°, except for a gap of 18°.

The 18° gap is located between the 63° bore upstream of the top dead center (TDC) and the 45° bore BTDC of cylinders 1 and 6 . Its purpose is to detect the TDC of cylinders 1 and 6  as well as the angle position of the crankshaft.

Each bore (2) triggers an pulse in the crankshaft position sensor. As soon as the engine management control unit receives a pulse from the crankshaft position sensor, it starts an internal counter. Calculations yield the crankshaft position and the engine speed.

Calculation of intermediate values makes it possible for the engine management control unit to accurately determine the start of injection and the injection period to within a fraction of a degree.

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Calculating the compression stroke on cylinder 1 

The pulse wheel (5) located on the intake camshaft has 12 panel (3). These are spread across the entire circumference of the pulse wheel (5) at a distance of 30°. There is an additional panel (4) on the pulse wheel (5) upstream of the top dead center (TDC) of cylinder 1.

As soon as the exhaust camshaft is rotating, the panels (3) as well as the additional panel (4) in the camshaft position sensor generate changes in the magnetic field. These are converted into shift signals by an electronic analysis system and forwarded to the engine management control unit.

If the engine is started, the engine management control unit uses the additional panel (4) to check when cylinder 1 is in its compression cycle.

The engine management control unit calculates the position of the crankshaft via the crankshaft position sensor at the same time. It adjusts the position of the additional panel (4) to the position of the gap on the flywheel (1). The signals from the crankshaft position sensor alone are then sufficient for determining the compression stroke of cylinder 1, and hence the start of activation of cylinder 1 to 6 (Y608 to Y613) fuel injectors.

Calculating the fuel temperature
The fuel temperature is calculated by the engine management control unit via the fuel temperature sensor.
There is a temperature-dependent resistor with negative temperature coefficients (NTC) inside the fuel temperature sensor.
If the fuel temperature sensor malfunctions, the engine management continues to operate with substitute values.

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Calculating the coolant temperature
For the purpose of fan control and in order to determine the actuation start as well as the actuation period (=injection quantity) of the fuel injectors, the engine management control unit exclusively uses measurements from the coolant outlet temperature sensor.
There is a temperature-dependent resistor with negative temperature coefficients (NTC) inside the coolant outlet temperature sensor.
If the sensor malfunctions, the engine management control unit continues to operate with substitute values. This allows the engine to be started even under unfavorable conditions and for the vehicle to continue to be driven.
To protect the engine from overheating, the engine management control unit limits the specified engine torque if the coolant temperature reaches an impermissibly high value.

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Calculating the air mass
Calculation of the air mass occurs via the engine management control unit. It uses the information from the following sensors:

 Fresh air differential pressure sensor

 Charge air pressure and temperature sensor

 Charge air temperature sensor in charge air distributor

 Oxygen sensorOn the basis of these values, the engine management control unit determines the air mass of the fresh air that has actually been suctioned or supercharged and the volume of the exhaust gases that have actually been recycled.

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