Look at the diagram to know how the injection system works, what injection system components are, what their types are, and what are the features of central, manifold, and direct injection.
Fuel injection
A fuel injection system is a system for dosing fuel in an internal combustion engine by means of an injector. Different types of fuel injection systems have various characteristics that affect the environmental class of the engine, its power, and fuel efficiency.
Types of Fuel Injection Systems
There are two ways fuel injection into the airflow: vacuum and excess pressure. For example, in a carburetor injection occurs due to vacuum, and in modern systems — due to excess pressure.
Carburetor
A carburetor is a device of the fuel injection system. It controls and mixes air and fuel entering the engine. The primary method of carburetor operation is adding fuel to the airflow passing through the narrowing of the carburetor (the Venturi tube). The carburetor automatically maintains the required fuel-to-air ratio in proportional volumes.
Single injection (Central injection)
This system provides the fuel injection with a single injector mounted on the engine intake manifold. The most popular central injection system is the Mono-Jetronic solutions from R.R. Bosch and Opel-Multec.
The main task of mono-injection was to find an alternative to the carburetor injection system. It was important to find a more efficient fuel injection system that could meet increased environmental requirements.
Mono-Jetronic: structural elements
Pressure regulator. It maintains the operating pressure in the injection system at a stable level, and after turning off the internal combustion engine maintains residual pressure in the system. This is important to facilitate start-up and create barriers against the formation of vapor locks.
Solenoid valve (injector). It creates the pulse fuel injection. The valve is controlled by an electrical signal. It comes from the control unit.
Throttle valve. Incoming air volume regulator.
Drive unit. He is responsible for the operation of the throttle valve.
Electronic control unit. «Brain», synchronizer.
Input sensors (injection timing, throttle position, engine speed, oxygen concentration, etc.).
Multi-point injection
Multi-point injection is based on the supply of fuel by a separate injector to the pre-chamber located in front of the intake valve of each engine cylinder. The injection is either pulsed or continuous.
The implementation of these solutions became possible thanks to electronic controls such as K-Jetronic and KE-Jetronic. This system has improved the technical and economic characteristics of cars, such as the level of fuel efficiency and the level of emissions of harmful substances in the exhaust.
In K/KE-Jetronic systems, fuel was injected continuously into the mixing chamber in front of the intake valve. In this case, quantitative dosing of fuel entering the air flow was carried out through interconnected “flow meter – dispenser” units.
In addition to the dispenser-distributor, an obligatory element of the solution is a throttle valve located behind the dispenser. The first versions had vacuum-mechanical fuel correction valves (the valves can be put into operation both from thermostats and from air discharge in the intake manifold), in later modifications electric valves appeared fuel correction. In addition, the systems began to be equipped with an oxygen sensor (lambda sensor). A huge advantage of the circuit design was that the injection system could be equipped with a catalyst, but there were significant questions regarding the level of reliability.