The fuel supply system based on its forced metered injection into the channels of the intake manifold or directly into the cylinder is called injection. In fact, the word "injector" means an injector, but in everyday life it is used to refer to the entire fuel supply system.
The main difference between an injector and a carburetor is the presence of injectors and their electronic control. The quantity, frequency and moment of fuel delivery is monitored using an electronic controller that interprets the readings of a number of sensors. There are two main types of such systems: single injection and distributed injection. The latter, in turn, is divided into several classes (direct, simultaneous, pairwise-parallel, phased).
The mass use of cars with an injector began in the 80s of the twentieth century. And at the moment, the injector is the most common fuel delivery system. The system gained such popularity due to economical fuel consumption and greater power.
Types of fuel injection systems
Depending on the number and location of injectors, several types of injectors are distinguished. Mono-injection means the presence of one nozzle installed at the mouth of the air manifold, and distributed one - per nozzle for each manifold channel or piston cylinder (there are also combined options).
In essence, such a system is an improvement on the carburetor. But unlike it, the mono injection is equipped with an electronic control unit (ECU) that reads a number of parameters and controls the nozzle.
Monoinjection loses to the distributed spray in a number of parameters, so new cars are no longer supplied with it. However, on the roads, you can still find cars with this type of injector.
The presence of an injector on each inlet channel allows more precise control of fuel consumption. This injector design is also variable. In the process of technology development, several main classes of distributed injection have emerged:
- Direct differs from the others in that the injectors are located in the cylinder head and supply fuel directly to the combustion chamber.
- Simultaneous injection means that the injectors are synchronized and they all deliver fuel at the same time.
- Parallel injection only works during engine start. The injectors work in pairs: one opens at the intake stroke, the second - at the exhaust.
- Phased injection synchronizes the injector with the movement of a specific piston, it opens at the intake stroke.
Thus, some types of multipoint injection relate to injector modes rather than to individual classes of fuel delivery systems. In addition, combined systems have their own nuances of work, in which the injectors are installed both on the intake ducts of the manifold and in the cylinder head.
Types of nozzles
In addition to different types of injector as a whole, there are also different designs of nozzles.
Electromagnetic injectors are most commonly used in direct injection engines. In them, the nozzle is blocked by a needle on the solenoid valve. When voltage is applied, the valve displaces the needle, opening the path for fuel delivery. The needle is returned to its original closed position by a spring.
Diesel engines with an injector, due to the higher fuel density, operate at a higher pressure. Therefore, they are supplied with electro-hydraulic nozzles. Their principle of operation is based on the use of fuel pressure in the line and is combined with the same solenoid valve.
From a technological point of view, the most efficient type of nozzles are piezoelectric. Mainly due to the higher response speed. As the main element, they use not an electromagnetic valve, but a piezoelectric crystal, which changes its length under the action of an electric current.
The principle of operation of the injector
The operation of the fuel injection system is based on the interpretation of the readings of a number of sensors and the corresponding ECU commands. The fuel supply process is as follows:
- The ECU receives data from the mass air intake sensor, throttle and crankshaft position, air temperature and other recording devices.
- The electronic unit analyzes the received data, and on their basis determines the required amount of fuel for the correct saturation of the mixture.
- The corresponding control signal is then sent to the injector valves and they inject the required amount of fuel.
During engine operation, the cycle repeats many times per second, so that the computing unit can respond to changes in the received sensor readings by adjusting the fuel mixture.
Common malfunctions of the injector
Given the technological complexity of the fuel injection system, you should be careful about its condition and maintenance. The failure of one of the components disrupts the operation of the entire system, and careful diagnostics and appropriate repairs are required to eliminate the problem. Let's consider the most common faults.
No fuel is supplied to the injector. Most likely the fault is on the side of the fuel line. A common cause is a breakdown of the fuel pump, a clogged fuel filter, or a physical obstruction of a section of the line.
The increase in flow is most likely due to clogged nozzle outlets. Deposits disturb the shape of the ejected jet with all the ensuing consequences, including increased consumption.
Idling periodically disappears as a result of a violation of the integrity of the air passages or breakdowns of the idle speed regulator located in the area of the throttle valve. A defective throttle position sensor can lead to oversupply of fuel.
Incorrect operation of other sensors (oxygen, coolant temperature, etc.) also negatively affects the operation of the entire power unit.
See also : Which is better injector or carburetor.
Injector pros and cons
Compared to carburetors, injectors have a number of advantages and disadvantages. The first include:
- stable operation (up to 150,000 km of run without breakdowns);
- high power;
- more economical fuel consumption (up to 30% with direct injection);
- no dependence on ambient temperature;
- less harmful emissions into the atmosphere;
- No spark plug flooding problems due to precise fuel metering and injection control;
The injectors also have disadvantages that need to be mentioned:
- the complexity of the design also complicates the repair (especially in the field);
- higher probability of breakage;
- expensive spare parts;
- high demands on fuel quality.
See also : Causes of lean mixture on injector.