General information
Fuel is drawn from the fuel tank by an electric fuel pump and supplied through a fuel filter to the fuel rail. The pressure regulator maintains the pressure in the fuel system within the range 3.2÷3.6 atm.
The fuel is injected pulsed into the intake manifold, located directly in front of the engine intake valves, via electrically controlled injectors. The engine control unit sequentially controls the injectors in accordance with the ignition sequence, regulates the injection time and thus the amount of fuel injected.
The air required to form the fuel mixture is sucked into the engine through the air filter and passes through the throttle valve and the intake manifold to the intake valves. The amount of air sucked in is regulated by the throttle valve, which is moved by a stepper motor controlled by the engine control unit. In compressor engines, the sucked air is compressed by a compressor driven by a V-belt transmission. The compressed air is then cooled in the charge air cooler and fed to the engine to form the fuel mixture.
The volume of air sucked in is determined by the air volume meter. The meter is located in the air intake duct. The meter housing contains a thin, electrically heated sensor plate, cooled by the flow of sucked air. The electric current that heats the plate is regulated by the control system in such a way as to maintain the temperature of the plate constant. If, for example, the amount of air sucked in increases, the temperature of the heated plate begins to decrease. At the same time, the magnitude of the electric current immediately increases in order to maintain the temperature of the plate constant. Fluctuations in the electric current of the plate indicate to the engine control unit its load status, which allows the amount of fuel to be injected to be correctly determined.
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 time, injection moment and the amount of fuel injected. At the same time, the operation of the control unit is coordinated with other systems of the car, for example, with the gearbox control or anti-theft system.
Information from other sensors and control voltages supplied to the actuators ensure optimal engine operation in any situation. If some sensors fail, the control unit switches to the emergency program mode to prevent possible engine damage and ensure further movement of the vehicle. In this case, the engine runs unevenly and tends to stall when the gas is increased.
Composition and operating principle
The location of individual elements of the engine management system using individual models as an example is shown in the illustration Front Door Control Module Installation Details.
The standard models under consideration, manufactured up to 12.2000, use a 6-pin (A-F) electronic control module (ECM) ME 2.0. The AMG models, as well as the standard models manufactured from 12.2000, use a 5-pin (1-5) module ME 2.8, which is housed in a sealed aluminum protective casing.
ECM Input Signals
The ECM uses signals from the following information sensors/actuators as input data:
- Coolant Temperature (ECT) Sensor;
- Hot-wire air mass flow (MAF) sensor;
- Intake Air Temperature (IAT) sensor integrated into the MAF assembly;
- Throttle Position Sensor (TPS);
- Engine oil level/temperature/quality sensor;
- Cruise control switch/Speedtronic 1);
- Fuel tank pressure sensor 1);
- Intake manifold pressure sensor 1)2);
- AT position sensor (PNP), - from the transmission control module (ETC);
- Differential Crankshaft Position (CKP) Sensor;
- Hall Effect Camshaft Position (CMP) Sensor;
- Oxygen sensors (lambda probes);
- Knock Sensors (KS);
- Sensor (potentiometer) gas pedal position.
1)Models for the American market
2) AMG trim models (ME 2.8 from 6.00)
ECM output signals
ECM output commands include:
- Ignition coil activation signals (one dual coil per cylinder);
- Fuel Injector Activation Signals;
- Throttle actuator activation signals;
- Fuel Pump Relay Activation Signals;
- Output component of the pulse width modulation (PWM) signal of the exhaust gas recirculation (EGR) transducer;
- Air mixing system activation signals;
- Intake manifold switch actuator activation signals;
- Starter Relay Activation Signals;
- Evaporative Emissions (EVAP) Canister Purge Activation Signals;
- Carbon Adsorber Shut-Off Valve Activation Signals 1);
- Fault memory data line signals.
1) Models for the American market
Information transmitted via the CAN data bus
- Operating status of the transmission control system (ETC);
- Operating condition 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 overload protection;
- Wheel speed (speed of movement and acceleration);
- Brake Light Switch Sensor Status;
- Status of instrument cluster gauges/indicators;
- Status of the K/V system (on/off, working pressure in the refrigeration system);
- Cruise control/Speedtronic switching signals.
Brief description of the operating principles of some of the sensors/actuators of the control system
Throttle Position Sensor (TPS) is mounted in the throttle actuator and provides the control module (ECM) with information about the current throttle angle. The second potentiometer provides the ECM with data about the base value and generates a backup signal if the throttle potentiometer fails.
Engine oil level/temperature/quality sensor is installed in the engine oil pan and generates three pulse width modulation (PWM) data signals transmitted to the ECM and (via CAN bus) on the vehicle's instrument cluster.
Note: Oil quality is determined based on the date of its last change.
Crankshaft Position Sensor (CKP) screwed into the cylinder block near the flywheel. It transmits information to the control unit about the engine speed and the TDC position of the piston of the first cylinder.
Camshaft Position (CMP) Sensor is located at the end of the cylinder head cover. Together with the crankshaft position sensor, it transmits information about the TDC of the piston of the first cylinder to the control unit. It serves to synchronize the ignition timing and ignition sequence.
Throttle actuation mechanism consists of an electric motor and two potentiometers. The mechanism regulates the position of the throttle valve, ensuring stability of idle speed, regardless of the connection of additional energy consumers, such as a power steering or air conditioning compressor.
Accelerator pedal position sensor is located in the area of the driver's feet 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, as well as from the throttle potentiometer.
Coolant Temperature (ECT) Sensor is located in the thermostat housing. It is a resistor with a negative temperature coefficient (NTC), the resistance of which decreases with increasing temperature.
Mass Air Flow (MAF) Sensor is a hot-wire anemometer mounted in the engine's air intake tract. The information provided by the sensor is used by the ECM to determine the air-fuel mixture dosage parameters.
Intake Air Temperature (IAT) sensor, - NTC resistor built into the MAF sensor assembly.
Fuel Tank Ventilation/Evaporative Emissions (EVAP) System 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, the fuel vapors accumulated in the adsorber are drawn into the intake tract and sent to the combustion chambers.
Lambda probes (oxygen sensors) 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.
Knock sensor(s) (KS) it is screwed directly into the cylinder block body and serves to prevent the occurrence of dangerous shock combustion of the fuel mixture, allowing the ignition timing to be maintained at the detonation limit, when the engine efficiency is maintained at the maximum level with minimum fuel consumption.
Air mixing system consists of an air pump installed in the front part of the power unit and synchronously functioning combination valves-switches, bolted to the front of each of the cylinder heads.
Exhaust gas recirculation system. The combined EGR valve with an electronic vacuum transducer is installed under the right cylinder bank. 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 reduce nitrogen oxide (NOX) emissions into the atmosphere. The valve opens at a vacuum depth of 80÷220 mbar.