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. At the same time, the 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:

- The intake air mass and its temperature via the left hot film MAF sensor (B2/6) with the integrated intake air temperature sensor (B2/6b1) and via the right hot film MAF sensor (B2/7) with the 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

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

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

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

- Left O2 sensor upstream of catalytic converter (G3/3) and right O2 sensor upstream of catalytic converter (G3/4), for residual oxygen content in exhaust gas

- Left pressure differential sensor (DPF) (B28/12) (with code (474) Particulate filter)

- Right pressure differential sensor (DPF) (B28/13) (with code (474) Particulate filter)

- Left catalytic converter exhaust gas temperature sensor (B16/4)

- Right catalytic converter exhaust gas temperature sensor (B16/5)

- Temperature sensor upstream of left turbocharger (B16/9)

- Temperature sensor upstream of right turbocharger (B16/10)

- Two-disk thermostat heating element (R48)

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

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The CDI control unit is in connection with the following control units via the drive train LIN:

- Alternator (G2)

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

The CDI control unit also communicates via the central CAN with the following control units to receive associated influencing variables:

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

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The CDI control unit communicates via the chassis CAN with the following control units to receive associated influencing variables:

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

- With the EIS [EZS] control unit (N73)

- With the steering column module (N80), signals from the CC [TPM] switch (S40/4), signal from the left steering wheel gear shifter (S110/2) and right steering wheel gear shifter (S111/2)

In order to obtain information about which gear is engaged, the CDI control unit communicated via the drive train CAN with the fully integrated transmission control (VGS) control unit (Y3/8n4).

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).