CDI driving mode, function

General function requirements

 Circuit 61 ON

 Vehicle rolling

Common rail diesel injection (CDI) driving mode - general

The basic tasks of the CDI in automotive operation include providing an engine torque, which matches the driver's requirements.

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At the same time, CDI should provide for ideal smooth running characteristics at the lowest possible fuel consumption and minimal exhaust emissions. For this purpose, the CDI control unit (N3/9) must match the CDI and the air and exhaust system according to the stored performance map data.

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For this purpose, the CDI control unit evaluates the following sensor information:

- Intake air mass and temperature, from the LH hot film MAF sensor (B2/6) with integrated intake air temperature sensor (B2/6b1) and from the RH hot film MAF sensor (B2/7) with integrated intake air temperature sensor (B2/7b1)

- Rail pressure sensor (B4/6/)

- Charge pressure sensor (B5/1)

- Coolant temperature sensor (B11/4)

- Charge air temperature sensor (B17/8)

- Pressure sensor downstream of air filter (B28/5), for the vacuum in the intake manifold

- Accelerator pedal sensor (B37), for a driver request

- Fuel temperature, through the fuel temperature sensor (B50)

- Crankshaft Hall sensor (B70), for the engine speed

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- Fuel filter condensation sensor with heating element (B76/1), on vehicles with code (U41) fuel/water separator and lubrication pack, for water level in the fuel main filter

- O2 sensor upstream of CAT (G3/2), for the residual oxygen content in the exhaust

- Pressure differential sensor (DPF) (B28/8), on vehicles with code (474) particulate filter, for the load condition of the diesel particulate filter (DPF)

- Temperature sensor upstream of diesel particulate filter (B19/9), on vehicles with code (474) particulate filter

- Temperature sensor upstream of turbocharger (B19/11)

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The CDI control unit is connected with the following components over the drive LIN:

- Alternator (G2)

- Glow time output stage (N14/3), glow function control

The CDI control unit also communicates via the vehicle dynamics CAN with the following control units to obtain the related variables:

- ESP control unit (N47-5), e.g. ESP torque request, wheel speeds

- EIS control unit (N73), interface to the Interior CAN, for example for the air conditioning switching status

- DIRECT SELECT gear selector switch(S16/13)

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The CDI control unit also communicates with the following control units over the central CAN, to obtain the related variables:

- The instrument cluster (A1), for the winter tire maximum speed, Electronic Stability Program (ESP) roll test mode

The CDI control unit also communicates via the drive train CAN with the following control units to maintain associated influencing variables:

- The fully integrated transmission control unit (Y3/8n4), for actual gear engaged

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When driving, the following function sequences are active; they are described in separate documents:

 Fuel supply

 Injection control

 Quantity Control

 Quantity mean value adaptation

 Zero quantity calibration

 Sliding operation

 Preglow

 Engine torque request

 Heat management

 Alternator interface

 Intake port shutoff

 Charging

 Exhaust gas recirculation

 Emission control

 The vehicle speed is governed to a max. of 250 km/h.

 The engine speed is governed to approx. 4500 rpm. This counteracts mechanical damage to the engine caused by overrevving. Above an engine speed of around 4500 rpm, the CDI control unit interrupts actuation of the fuel injectors (Y76) and reduces the fuel pressure in the rail via the quantity control valve (Y94) and the pressure control valve (Y74).