Diagram of the digital engine control system (DME)
1 - adsorber
2 - shut-off valve
3 - fuel tank ventilation valve
4 - fuel pressure regulator
5 - injector
6 - pressure transmitter
7 - ignition coil
8 - position sensor
9 - secondary air pump
10 - shut-off valve
11 - air mass meter
12 - control device
13 - throttle sensor
14 - idle speed adjuster
15 - air temperature sensor
16 - exhaust gas recirculation valve
17 - fuel filter
18 - knock sensor
19 - speed sensor
20 - engine temperature sensor
21 - oxygen sensor
22 - diagnostic connector
23 - diagnostic lamp
24 - differential pressure sensor
25 - fuel pump
Sensors for the injection system of gasoline engines
Fuel is sucked in from the fuel tank by an electric fuel pump located in the fuel tank and fed through the fuel filter to the injectors. The pressure regulator maintains the fuel pressure in the system constant.
The injectors are electrically controlled and inject fuel in pulses into the intake manifold ahead of the engine intake valves.
Air is drawn in by the engine through the air filter and is supplied through the throttle assembly and intake piping to the intake valves.
The quantity of fuel injected is determined primarily by the mass of the intake air. The intake air mass is determined by a meter located in the intake manifold. In the body of the mass meter there is a thin, electrically heated plate, which is cooled by a passing air stream. The control system changes the value of the heating current so that the temperature of the plate remains constant. If, for example, the amount of air taken in increases, the plate tends to cool down. As a result, the value of the plate heating current increases. From deviations in the heating current, the engine management system determines the mass of air and accordingly regulates the amount of injected fuel.
Information coming from various sensors and commands coming to the executive bodies ensure optimal engine operation in any mode. If the sensors fail, the control unit switches to emergency mode to prevent damage to the engine and allow the vehicle to continue moving. The failure of the sensors should not necessarily be felt as a deterioration in the quality of the engine. However, no later than the next date for checking the exhaust gases, this data will be entered in the fault memory of the engine management system.
Idle speed adjuster controls the amount of air at idle bypassing the throttle. This ensures that a constant idle speed is maintained, regardless of the connection of additional consumers, such as a power steering or a cooling compressor.
Coolant temperature sensors and intake air temperature sensor report the current temperature value as a result of a change in the resistance of the resistor. As the temperature rises, the resistance decreases.
Fuel tank ventilation system consists of an adsorber and a shut-off valve. The adsorber accumulates fuel vapors formed as a result of fuel heating. When the engine is running, the vapors are sucked out of the adsorber and fed into the combustion chambers of the engine.
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.
Fuel pump relay located in the relay box above the glove box. The relay supplies current to the fuel pump.
Ignition system has no moving parts, there is no traditional ignition distributor. Each spark plug has its own coil.
Ignition Voltage Control System if the voltage is too low, disables the DME unit (e.g. due to cable damage). In this case, the engine cannot be started. This prevents damage to the catalytic converter.
Anti-knock control system serves to determine and regulate the optimum ignition timing for each cylinder. If a malfunction occurs in the ignition system, the fuel supply to the corresponding cylinder is cut off.
320i, 323i, 328i: Variable valve timing system (opening and closing times for intake and exhaust valves), shortly called Doppel VANOS, rotates both camshafts in relation to the sprockets at an angle that provides optimal valve timing in all engine operating modes, and therefore optimal idling, high torque characteristics and reduced fuel consumption. Turning is carried out under oil pressure. To do this, the DME regulates the oil pressure in the VANOS control element via an electrically controlled valve.
Adjustable inlet pipeline adjusts the length of the intake pipe depending on the engine speed. To do this, a rotary damper with pneumatic control is installed in the inlet pipeline. Long pipeline lengths at low speeds ensure good cylinder filling and thus higher torque due to resonance. With a high number of revolutions, the length of the suction tract is reduced, which increases the engine's power potential.