GF07.16-P-0001T Common Rail Diesel Injection (CDI), Function

GF07.16-P-0001T Common Rail Diesel Injection (CDI), Function

Diesel engine OM 642 is characterized by and excels due to the following basic innovations:
^ Common rail diesel injection (CDI) 4
^ V6 crankcase made out of aluminum instead of cast iron
^ Balance shaft located in the "V" of both cylinder banks which turns in an opposite direction to the crankshaft
^ Valve control with roller-type cam follower
^ Load level controlled pre and post injection
^ A flow dynamics optimized supercharging system consisting of a turbocharger with variable turbine geometry
^ Exhaust gas recirculation (AGR) with water-cooled exhaust gas recirculation cooler
^ Rapid glowing system with glow output stage (N14/3)
^ Highly efficient ventilation system with centrifugal oil separator

The CDI 4 takes account of the following features of the extended demands upon a common-rail injection system:
^ Use of piezo-injectors and thus more precise injections
^ Hydraulically optimized 8-hole nozzle module, except model 211.022 with OM 642.920 with code (494) USA version, except model 211.022/222 with OM 642.920 code (498) Japan version, except model 211.024 with OM 642.920
^ Hydraulically optimized 7-hole nozzle module on model 211.022 with 642.920 with code (494) USA version, on model 211.022/222 with OM 642.920 with code (498) Japan version and on model 211.024 with OM 642.920
^ Load-dependent, dual pre-injection to reduce combustion noise
^ Suction regulated high-pressure pump with, on average, a lower operating energy input for consumption reduction
^ Load-dependent, double post-injection in vehicles with code (474) Particulate filter
^ A maximum injection pressure of 1600 bar

CDI controls the following functions via the CDI control unit (N3/9):
^ Fuel supply in all operating conditions
^ Controlling the glow functions
^ Injection quantity control
^ Emission control
^ Charge pressure control
^ Shutting of the refrigerant compressor (A9)
^ Shut-off control

To do this, the CDI control unit reads in information from the following sensors:
^ Oil temperature sensor (B1)
^ Left hot film mass air flow sensor (B2/6)
^ Intake air temperature sensor (B2/6b1)
^ Right hot film mass air flow sensor (B2/7)
^ Intake air temperature sensor (B2/7b1)
^ Rail pressure sensor (/)B4/6
^ Boost pressure sensor (/)B5/1
^ Camshaft Hall sensor (B6/1)
^ Coolant temperature sensor (/)B11/4
^ Charge air temperature sensor (B17/8)
^ Pressure sensor downstream of the air filter (/)B28/5
^ Accelerator pedal sensor (B37)
^ Fuel temperature sensor (B50)
^ Exhaust back pressure sensor (B60)
^ Crankshaft Hall sensor (B70)
^ Fuel filter water level sensor (B76) for model 211.022 with diesel engine OM 642.920, with code (494) USA version
^ O2 sensor downstream of the catalytic converter (G3/1) on model 211.022 with OM 642.920, with code (494) USA version, on model 211.024 with OM 642.920, on model 211.022/222 with OM 642.920, with code (498) Japan version
^ O2 sensor upstream of the catalytic converter (G3/2), except model 211.022/222 with OM 642.920, with code (498) Japan version
^ Temperature sensor upstream of diesel particulate filter (B19/9), on vehicles with code (474) Particulate filter
^ Oil level indicator switch (S43)
^ CAT temperature sensor (B19), except model 211.022/222 with OM 642.920 with code (498) Japan version
^ Temperature sensor downstream of the catalytic converter (B19/8), on model 211.022/222 with OM 642.920 with code (498) Japan version
^ Temperature sensor upstream of the turbocharger (B19/11), on model 211.022 with OM 642.920 with code (494) USA version, on model 211.022/222 with OM 642.920 with code (498) Japan version, on model 211.024 with OM 642.920
^ Pressure differential sensor (DPF) (B28/8), on vehicles with code (474) Particulate filter

The CDI control unit actuates the following actuators:
^ Starter relay (N10/1kL)
^ Fuel pump relay (N10/2kA)
^ Throttle valve actuator (M16/6)
^ Intake port shutoff motor (M55)
^ Vent line heater element (R39/1)
^ Left exhaust gas recirculation positioner (Y27/9)
^ Pressure regulator valve (Y74)
^ Two-disk thermostat heating element (R48), on model 211.022 with OM 642.920 with code (494) USA version, on model 211.024 with OM 642.920
^ Cylinder 1 fuel injector (Y76y1)
^ Heater of the O2 sensor downstream of the catalytic converter on model 211.022 with OM 642.920 with code (494) USA version, on model 211.024 with OM 642.920, on model 211.022/222 with OM 642.920 with code (498) Japan version
^ Heater of the O2 sensor upstream of the catalytic converter, except model 211.022/222 with OM 642.920 with code (498) Japan version
^ Cylinder 2 fuel injector (Y76y2)
^ Cylinder 3 fuel injector (Y76y3)
^ Cylinder 4 fuel injector (Y76y4)
^ Cylinder 5 fuel injector (Y76y5)
^ Cylinder 6 fuel injector (Y76y6)
^ Quantity control valve (Y94)
^ Boost pressure positioner (Y77/1)

The CDI control unit communicates with the following components via the Local Interconnect Network (LIN):
^ Alternator (G2)
^ Glow time output stage

The CDI control unit is connected to the following control units via the Control Area Network Bus Class C (engine compartment) (CAN C):
^ Instrument cluster (A1)
^ Electronic selector lever module control unit (N15/5) for vehicles with transmission 722.9
^ ESP control unit (N47-5)
^ EIS [EZS] control unit (N73)
^ Steering column tube module (N80)
^ Central gateway control unit (N93)
^ Fully integrated transmission control (VGS) control unit (Y3/8n4) for vehicles with transmission 722.9

STAR DIAGNOSIS can be used to read out system errors that occur, which are stored in the fault memory of the CDI control unit. This also applies for system faults which occur in the glow system, which were recognized by the glow time output stage and transmitted via the drive LIN to the CDI control unit.

Fuel supply
The CDI is supplied with fuel by the fuel pump (M3). For this purpose, the CDI control unit actuates the fuel pump via the fuel pump relay, which delivers the fuel via the fuel main filter to the common rail high pressure pump.
For model 211.022 with diesel engine OM 642.920, with code (494) USA version, the fuel main filter is fitted with a fuel filter water level sensor for water level monitoring.
If the water level has reached the maximum value then this will be indicated to the driver in the instrument cluster.

According to actuation by the CDI control unit, the quantity control valve regulates the feed to the common rail high pressure pump. Excess to requirements fuel flows back over the return line into the fuel tank.

Control of the glow system at engine start and during driving mode
CDI actuates the glow time output stage via the CDI control unit. This in turn actuates the glow plugs (R9). The following glow types exist:
^ Preglowing
^ Start-ready glowing
^ Start-glowing
^ Afterglowing
^ Diagnostic glowing

Injection quantity control at engine start and during driving mode
The CDI controls the fuel injectors (Y76) via the CDI control unit depending on speed and load. A distinction is made between "preinjection", "main injection" and "post-injection".

Emission control system except model 211.022 with OM 642.920 and code (494) USA version, except model 211.024 with OM 642.920
The emissions output by the engine are cleaned in the exhaust system by a near-engine mounted catalytic convertor (TWC). The catalytic convertor is also used to reduce noise pollution. A lambda control is also used. On vehicles with code (474) Particulate filter, a diesel particle filter (DPF) is used.

Emission control system on model 211.022 with OM 642.920 and code (494) USA version, on model 211.024 with OM 642.920
The exhaust gases output by the engine are cleaned in the exhaust system by a near engine mounted oxidation catalytic convertor, a NOx catalytic convertor, a diesel particulate filter DPF and an odor filter.

Boost pressure control
The CDI actuates the boost pressure positioner via the CDI control unit by means of a pulse width modulation (PWM) signal.

The boost pressure positioner adjusts the position of the guide vanes in the turbocharger via a linkage. In this way the boost pressure is controlled. Thus a high boost pressure is possible even at low engine speeds.

Refrigerant compressor shut-off
Function requirements:
^ AC system activated
^ Engine speed < 2000 rpm
^ The values of the accelerator pedal sensor is > 95 %

The CDI control unit interrupts actuation of the refrigerant compressor. If the above listed function requirements are no longer met, the CDI control unit reactuates the refrigerant compressor.

Shut-off control
The function requirement for shutoff control "Circuit 15 OFF". Via the CDI control unit, CDI actuates the quantity control valve and the pressure regulator valve. The quantity control valve interrupts the supply to the common rail high pressure pump and the pressure regulator valve opens the connection to the return line.