In the engine with a displacement of 2.0 liters, fuel injection is carried out simultaneously by two nozzles through each revolution of the crankshaft. On other engines, injection occurs sequentially, in accordance with the firing order of the cylinders.
The air taken in by the engine passes through the air filter, throttle assembly and then goes to the intake valves.
Pic. 5.37. Mass Air Flow Sensor: 1 - plate
According to the mass of air entering the engine and measured by the mass air flow sensor (HFM), the required amount of injected fuel is determined. The mass air flow sensor has a sensitive heated plate 1 (pic. 5.37), cooled by the air passing through it. In order to keep the plate temperature constant, the amount of current changes according to the mass of the intake air. The engine control unit, by the amount of current received from the mass flow sensor, determines the required amount of injected fuel.
The electronic control unit, receiving signals from various sensors and controls, ensures optimal engine operation depending on driving conditions. If one of the sensors is damaged, the control unit goes into emergency mode to prevent engine damage and ensure the car moves to the nearest car repair shop. In this mode, the engine runs erratically and may stop when the accelerator pedal is pressed more.
Elements of the engine management system
The crankshaft position sensor is mounted on the cylinder block next to the flywheel ring gear. It reports the position and speed of the crankshaft to the control unit.
The camshaft position sensor is located on the cylinder head and indicates the position of the camshaft at the moment.
The throttle position sensor transmits a signal about its angular position.
The idle switch informs the control unit about the position of the throttle when the engine is idling. In this case, the full load switch signals that the throttle valve is in the position corresponding to the operation of the engine at full load.
The coolant temperature sensor is a resistor whose resistance decreases as the coolant temperature rises.
The intake air temperature sensor is similar to the coolant temperature sensor.
Fuel vapors from the fuel tank are captured by an absorber with a solenoid valve. Activated carbon accumulates fuel vapors, which, when the engine is running, as a result of the formation of a vacuum in the intake manifold, enter the cylinders, where they burn out.
Oxygen concentration sensor (Lambda probe) necessary for the correct operation of the catalytic converter, it gives the control unit a signal about the amount of oxygen in the exhaust gases, as a result, the control unit changes the fuel supply.
The idle speed control valve controls the amount of air that bypasses the throttle. The result is a constant engine speed, regardless of the number of consumers connected, such as the power steering pump or the air conditioning compressor.
Knock sensor (except for the 2.0 liter engine manufactured before 04.1996) designed to determine the optimal ignition timing.
Camshaft Adjuster (except for 2.0 l engines produced before 04.1996 and V6 engine). As a result of the action of the electro-hydraulic actuator, after the command of the control unit, the intake camshaft is rearranged relative to the chain drive. When moving in the direction «lag» engine idling becomes softer, respectively, when the engine is running at a high crankshaft speed, power is increased. At low and medium speeds of the crankshaft, early closing of the intake valves improves cylinder filling, resulting in increased torque.
The use of the so-called resonant intake pipe on inline 6-cylinder engines, which, depending on the crankshaft speed, changes the length of the intake tract to the cylinders, improves the torque characteristic.
Motronic ME electronic control system used on V6 and V8 engines
The Motronic ME system is an advanced HFM system. The fuel injectors, just like in the HFM system, work sequentially in accordance with the firing order of the cylinders. The main difference is that the throttle is controlled by an actuator, which, in turn, regulates the idle speed of the crankshaft. The accelerator pedal in this system is electronically connected to the engine control unit. An electronic sensor monitors the position of the pedal. The throttle valve is controlled by the control unit using a servomotor. The accelerator pedal control system has a built-in system that maintains a constant vehicle speed.