The operating principle of fuel injection systems of gasoline engines (Opel Vectra C)

At the dawn of the automobile industry, when designing internal combustion engines, the dependence of combustion efficiency and, accordingly, the return of internal energy of the working mixture on the proportion of fuel and air in its composition was revealed. For maximum efficiency, a strictly defined proportion is required, which must be maintained in all engine operating modes. This, in turn, leads to fuel economy. Maintaining this proportion is especially important for gasoline engines. Today, all gasoline engines of leading automotive manufacturers are equipped with an electronically controlled injection system. With this method of mixture formation, the air necessary for fuel combustion enters through the air filter and through the throttle valve into the intake manifold. The amount of incoming air is determined by the corresponding sensor. Fuel is sucked from the fuel tank by an electric pump, passed through the fuel filter and fed to the fuel distribution line. Through the injectors, the fuel is injected into the intake manifold, located in front of the intake valves of the cylinders, where it is mixed by the air flow.

Note: In the Z22YH engine, injection is carried out directly into the combustion chamber.

The engine control module, observing the ignition sequence, regulates the opening time of the injector channels and thus the amount of injected fuel. In addition, the ECM controls the throttle valve, regulating the amount of air supplied. Initially, to determine the amount of fuel supplied to the engine cylinders, only the incoming air flow was measured. But gradually new dependencies were identified that affect the efficiency of fuel combustion, and the requirements for the toxicity of exhaust gases became more stringent, which entailed. and the complication of engine management systems. Modern fuel injection control systems are. a complex set of sensors, control units, actuators and electronic circuits (see illustration 12.1). Below is a description of the operating principles of some of them:

• The accelerator pedal position sensor is mounted in the pedal assembly. From the sensor, the corresponding electrical signal is sent to the engine control module (ECM), setting the values for the desired driving mode of the car;
• The throttle control module contains the actuator (stepper motor) and a throttle potentiometer. The electric motor regulates the position of the throttle valve and allows maintaining a constant idle speed regardless of the connection of additional consumers. The potentiometer sends information to the ECM about the current value of the throttle valve installation angle;
• The camshaft position sensor provides the ECM with information about the ignition timing in the first cylinder of the engine to synchronize the ignition timing and injection sequence in the other cylinders;
• The air mass sensor housing contains a thin sensor plate through which an electric current is passed. The plate is cooled by the air flow. The control unit regulates the heating current so that the plate temperature remains constant. Current fluctuations during heating allow the ECM to determine the engine load condition and regulate the amount of fuel injected accordingly;
• The coolant temperature sensor is installed in the thermostat housing. It is an NTC resistor - as the coolant temperature increases, its resistance decreases and the corresponding signal is sent to the ECM;
• The knock sensor is mounted under the exhaust manifold in the cylinder block. It sets the ignition timing at the start of detonation combustion of the fuel, thereby preventing the process of detonation combustion of the fuel mixture on the one hand, and ensuring the most complete combustion of the fuel and reducing its consumption on the other hand.

Different systems may differ from each other in the number of elements involved, depending on the design of the power unit and the requirements for a specific engine. Independent intervention in the adjustment and configuration of these systems is not allowed. For this, special diagnostic and adjustment devices are used, which are usually available only at specialized service stations.