General information
Fuel is drawn from the fuel tank by the electric fuel pump and fed through the fuel filter to the fuel distribution line. The pressure regulator ensures that the pressure in the fuel system is maintained within the range 3.2÷3.6 atm.
Through electrically controlled injectors, fuel is injected in pulses into the intake manifold located directly in front of the engine intake valves. The engine control unit performs sequential control of the injectors in accordance with the ignition order, regulates the injection time and thus the amount of injected fuel.
The air necessary for the formation of the fuel mixture is sucked in by the engine through the air filter and enters through the throttle valve and intake pipe to the intake valves. The amount of air intake is controlled by a throttle valve, which is moved by a stepper motor controlled by the engine control unit. For compressor engines, the intake air is compressed by a compressor driven by a V-belt. The compressed air is then cooled in the charge air cooler and enters the engine to form the fuel mixture.
The intake air volume is determined by an air quantity meter. The meter is located in the intake air duct. In the meter housing there is a thin, electrically heated sensor plate, cooled by the passing flow of intake air. The electric current heating the plate is regulated by the control system in such a way as to keep the temperature of the plate constant. If, for example, the amount of intake air increases, the temperature of the heated plate starts to decrease. At the same time, the magnitude of the electric current immediately increases in order to keep the temperature of the plate unchanged. Fluctuations in the electric current of the plate indicate to the engine control unit its load condition, which allows it to correctly determine the amount of fuel injected.
The engine control unit is located in the electronics box, on the left, near the brake fluid reservoir or directly on the engine. The control unit determines the optimal ignition timing, injection timing and the amount of injected fuel. In this case, the operation of the control unit is coordinated with other vehicle systems, for example, with the control of the gearbox or the anti-theft system.
Information from other sensors and control voltages supplied to the executive bodies ensure optimal engine operation in any situation. If some sensors fail, the control unit switches to the emergency program mode in order to exclude possible damage to the engine and ensure the further movement of the car. In this case, the engine runs unevenly and tends to stop when the gas is increased.
Composition and principle of operation
The location of the individual elements of the engine management system for the example of individual models is shown in the illustration Front Door Control Module Installation Details.
Models in question come standard with 12.2000 release using a 6-pin (A-F) electronic control module (ECM) ME 2.0. On models of the AMG configuration, as well as on standard models of the release from 12.2000, a 5-pin is installed (1-5) ME 2.8 module, placed in a sealed aluminum protective casing.
ECM inputs
The ECM uses signals from the following information sensors/actuators as input:
- coolant temperature sensor (ECT);
- hot-wire intake air mass sensor (MAF);
- intake air temperature sensor (IAT), built into the MAF assembly;
- Throttle position sensor (TPS);
- Level / temperature / quality sensor of impellent oil;
- Tempostat/Speedtronic control switch1);
- Fuel tank pressure sensor1);
- Intake manifold pressure sensor1) 2);
- AT position sensor (PNP), - from the transmission control module (ETC);
- Differential crankshaft position sensor (CKP);
- Camshaft position sensor (CMP) on the Hall effect;
- oxygen sensors (lambda probes);
- knock sensors (KS);
- Sensor (potentiometer) gas pedal position.
1) Models for the US market
2) AMG equipment models (ME 2.8 from 6.00)
ECM Outputs
ECM output commands include:
- Ignition coil activation signals (one twin coil per cylinder);
- Fuel injector activation signals;
- Throttle actuator activation signals;
- Fuel pump relay activation signals;
- Output component of the pulse width modulation signal (PWM) exhaust gas recirculation system transducers (EGR);
- Signals for activating the air mixing system;
- Signals for activation of the intake manifold switching actuator;
- Starter relay activation signals;
- Activation signals for purge of the carbon adsorber of the evaporative emission control system (EVAP);
- Activation signals for charcoal canister cut-off valve1);
- Fault memory data line signals.
1) Models for the US market
Information transmitted via the CAN communication bus
- Operating condition of the transmission control system (ETC);
- Operational status of dynamic motion stabilization systems (BAS/ASR/ESP/ETC), - control module;
- Working condition of the electronic gas pedal
- Information about the current position of the AT;
- Information on transmission protection against overloads;
- Wheel speed (movement speed and acceleration);
- The state of the sensor-switch of brake lights;
- Status of instrument cluster meters/indicators;
- A/C system status (on / off, working pressure in the refrigeration path);
- Tempostat/Speedtronic switching signals.
Brief description of the principles of operation of some of the sensors / actuators of the control system
Throttle position sensor (TPS) mounted in the throttle actuator and outputs to the control module (ECM) information about the current throttle angle. The second potentiometer provides the ECM with a base value and provides a backup signal if the throttle potentiometer fails.
Level/Temperature/Engine Oil Quality Sensor installed in the engine crankcase and generates three pulse-width modulation information signals (PWM), transmitted to the ECM and (via CAN bus) to the vehicle's instrument cluster.
Note. The quality of the oil is determined based on the date of the last oil change.
crankshaft position sensor (CKP) screwed into the cylinder block at the flywheel. It transmits to the control unit information about the engine speed and the TDC position of the piston of the first cylinder.
Camshaft position sensor (CMP) located at the end of the cylinder head cover. Together with the crankshaft position sensor, it transmits to the control unit information about the TDC of the piston of the first cylinder. It serves to synchronize the ignition timing and ignition sequence.
Throttle actuator consists of an electric motor and two potentiometers. The mechanism regulates the position of the throttle valve, ensuring the stability of the idle speed, regardless of the connection of additional consumers of energy, such as a power steering or an A/C compressor.
Gas pedal position sensor located in the area where the driver's feet are located directly on the axis of the gas pedal. It informs the control unit about the position of the pedal. For safety reasons, an additional signal is taken from the pedal sensor, in the same way as from the throttle potentiometer.
coolant temperature sensor (ECT) located in the thermostat housing. It is a negative temperature coefficient resistor (NTC), whose resistance decreases with increasing temperature.
Air mass sensor (MAF) is a hot-wire anemometer mounted in the engine air intake tract. The information provided by the sensor is used by the ECM to determine the air/fuel ratio.
intake air temperature sensor (IAT), - NTC resistor built into the MAF sensor assembly.
Fuel Tank Ventilation/Fuel Evaporation System (EVAP) consists of a carbon adsorber and an electromagnetic valve for controlling the purge of the latter. The adsorber accumulates fuel vapors formed as a result of its heating. When the engine is running, fuel vapor accumulated in the adsorber is drawn into the intake tract and sent to the combustion chambers.
lambda probes (oxygen sensors) they measure the oxygen content in the exhaust gases before and after the catalytic converter and transmit the corresponding signals to the engine control unit. One lambda probe is located before and the other after the catalytic converter.
Sensor (And) detonation (KS) is screwed directly into the body of the cylinder block and serves to prevent the occurrence of dangerous impact combustion of the fuel mixture, allowing you to keep the ignition timing at the knock limit, when the efficiency of the engine output is maintained at a maximum level with a minimum fuel consumption.
Air mixing system consists of an air pump installed in the front of the power unit and synchronously functioning combined switching valves, bolted to each of the cylinder heads in front.
Exhaust gas recirculation system. A combined EGR valve with an electronic vacuum transducer is installed under the right bank of cylinders. The transducer is controlled by a PWM signal generated by the ECM. Mixing a certain amount of exhaust gases into the engine intake tract helps to reduce the emission of nitrogen oxides into the atmosphere (NOx). The valve is opened at a vacuum depth of 80÷220 mbar.