In recent years, almost all vehicles on the market use injection fuel supply systems. The main reason is that they have to respond to increasingly stringent environmental regulations. The fuel injection system has evolved from the early mechanical single-point injection to the current electronic multi-point injection. Then, what are single-point injection and multi-point injection? Assuming a four-cylinder engine, from a single injector to the branch of the intake manifold, the fuel is injected from one place and then distributed to the four cylinders with the intake air. This is a single point injection; In the intake port of each of the four cylinders, because each cylinder has one fuel injection nozzle, the four-cylinder engine has four fuel injection nozzles. This is called multi-point injection.
From the perspective of the fuel path, first, the fuel pump sends the fuel from the fuel tank to the fuel pipeline, and the fuel pipeline sends the fuel to the fuel rail. The fuel rail is controlled by the pressure regulating valve to control the fuel pressure and ensure the fuel delivered to each cylinder. The pressure can all be the same. On the other hand, the pressure regulating valve will also send excess oil to the oil return pipe and flow back into the oil tank by releasing the pressure. One end of the fuel injection nozzle is connected to the fuel rail, and the nozzle is on the air inlet of each cylinder. The engine ECU will issue a fuel injection command to the fuel injector according to the engine operating status. The fuel injection quantity is determined by the fuel pressure and the fuel injection time of the fuel injector. The fuel pressure at the fuel rail is controlled by the pressure regulating valve, and the fuel is regulated. The pressure of the pressure valve is adjusted by the manifold vacuum (engine load), so the ECU can control the fuel injection time. When the engine needs more fuel, the fuel injection time will be longer, otherwise the fuel injection time will be shorter.
The injector itself is a normally closed valve (normally closed valve means that the valve is always closed when there is no input control signal; while the normally open valve is the valve is always open when no control signal is input). A valve needle moves up and down to control the opening and closing of the valve. When the ECU issues a fuel injection command, its voltage signal will cause current to flow through the coil in the fuel injection nozzle, generating a magnetic field to suck up the valve needle, and open the valve so that the fuel can be ejected from the fuel injection hole.
The biggest advantage of fuel injection is that the control of fuel supply is very precise, allowing the engine to have the correct air-fuel ratio in any state. Not only does it keep the engine running smoothly, but its exhaust gas can also comply with environmental regulations.