In the case of fuel injection, your engine is still ​sucking, but instead of relying solely on the amount of fuel being sucked in, the fuel injection system fires exactly the right amount of fuel into the combustion chamber. Fuel injection systems have already gone through several stages of evolution, electronics have been added to them - this was perhaps the biggest step in the development of this system. But the idea of ​​such systems remains the same: an electrically activated valve (injector) sprays a measured amount of fuel into the engine. In fact, the main difference between a carburetor and an injector is precisely in the electronic control of the ECU - it is the on-board computer that supplies exactly the right amount of fuel to the engine combustion chamber.

Let's see how the fuel injection system and the injector in particular work.

What does the fuel injection system look like?

If the heart of a car is its engine, then its brain is the engine control unit (ECU). It optimizes the performance of the motor by using sensors to decide how to control some of the actuators in the motor. First of all, the computer is responsible for 4 main tasks:

1. manages the fuel mixture,
2. controls idle speed
3. is responsible for the ignition timing,
4. controls the valve timing.

Before we talk about how the ECU performs its tasks, let's talk about the most important thing - let's trace the path of gasoline from the gas tank to the engine - this is the work of the fuel injection system. Initially, after a drop of gasoline leaves the walls of the gas tank, it is sucked up by an electric fuel pump into the engine. Electric fuel pump, as a rule, consists of the pump itself, as well as a filter and a transmission device.

The fuel pressure regulator at the end of the vacuum-fed fuel rail ensures that the fuel pressure is constant with respect to the suction pressure. For a gasoline engine, fuel pressure is typically on the order of 2-3.5 atmospheres (200-350 kPa, 35-50 PSI (psi)). The fuel injectors are connected to the engine, but their valves remain closed until the ECU allows fuel to be sent to the cylinders.

But what happens when the engine needs fuel? This is where the injector comes into play. Usually injectors have two pins: one pin is connected to the battery through the ignition relay, and the other pin goes to the ECU. The ECU sends pulse signals to the injector. Due to the magnet, to which such pulsating signals are applied, the injector valve opens, and a certain amount of fuel is supplied to its nozzle. Since there is a very high pressure in the injector (the value is given above), the opened valve sends fuel at high speed to the nozzle of the injector nozzle. The duration with which the injector valve is open affects how much fuel is supplied to the cylinder, and this duration, respectively, depends on the pulse width (i.e., how long the ECU sends a signal to the injector).

When the valve opens, the fuel injector sends fuel through the spray tip, which atomizes the liquid fuel into mist, directly into the cylinder. Such a system is called direct injection system. But the atomized fuel may not be supplied immediately to the cylinders, but first to the intake manifolds.

How the injector works

But how does the ECU determine how much fuel needs to be supplied to the engine at the moment? When the driver presses the accelerator pedal, he actually opens the throttle by the amount of pedal pressure, through which air is supplied to the engine. Thus, we can confidently call the gas pedal the "air regulator" to the engine. So, the car's computer is guided, among other things, by the throttle opening value, but is not limited to this indicator - it reads information from many sensors, and let's find out about them all!

Mass air flow sensor

First things first, the Mass Air Flow (MAF) sensor detects how much air is entering the throttle body and sends that information to the ECU. The ECU uses this information to decide how much fuel to inject into the cylinders to keep the mixture in ideal proportions.

Throttle position sensor

The computer constantly uses this sensor to check the throttle position and thus learn how much air is passing through the air intake in order to regulate the pulse sent to the injectors, ensuring that the correct amount of fuel enters the system.

Oxygen sensor

In addition, the ECU uses the O2 sensor to find out how much oxygen is in the car's exhaust. The oxygen content of the exhaust gases provides an indication of how well the fuel is burning. Using linked data from two sensors: oxygen and mass air flow, the ECU also controls the saturation of the fuel-air mixture supplied to the combustion chamber of the engine cylinders.

crankshaft position sensor

This is perhaps the main sensor of the fuel injection system - it is from him that the ECU learns about the number of engine revolutions at a given time and corrects the amount of fuel supplied depending on the number of revolutions and, of course, the position of the gas pedal.

These are the three main sensors that directly and dynamically affect the amount of fuel supplied to the injector and subsequently to the engine. But there are a number of other sensors:

• The voltage sensor in the electrical network of the car is needed so that the ECU understands how low the battery is and whether it is necessary to increase the speed in order to charge it.
• Coolant temperature sensor - ECU increases the number of revolutions if the engine is cold and vice versa if the engine is warm.

The first injection systems were mechanical (Figure 2.61) rather than electronic, and some of them (such as the high-performance BOSCH system) were extremely ingenious and worked well. The first mechanical fuel injection system was developed by Daimler Benz, and the first mass-produced car with gasoline injection was produced back in 1954. The main advantages of the injection system compared to carburetor systems are as follows:

The absence of additional resistance to the air flow at the inlet, which takes place in the carburetor, which ensures an increase in the filling of the cylinders and the liter engine power;

More accurate distribution of fuel to individual cylinders;

Significantly higher degree of composition optimization combustible mixture in all operating modes of the engine, taking into account its condition, which leads to an improvement in fuel economy and a decrease in exhaust gas toxicity.

Although in the end it turned out that it was better to use electronics for this purpose, which makes it possible to make the system more compact, more reliable and more adaptable to the requirements of various engines. Some of the first electronic injection systems were carburetors that removed all "passive" fuel systems and installed one or two injectors. Such systems are called "central (single-point) injection" (Fig. 2.62 and 2.64).

Rice. 2.62. Central (single point) injection unit

Rice. 2.64. Scheme of the central fuel injection system: 1 - fuel supply;

Rice. 2.63. Electronic control unit 2 - air intake; 3 - throttle valve for a four-cylinder engine; 4 - inlet pipeline; Valvetronic BMW 5 - nozzle; 6 - engine

At present, distributed (multi-point) electronic injection systems are most widely used. It is necessary to dwell on the study of these nutritional systems in more detail.

POWER SYSTEM WITH ELECTRONIC DISTRIBUTED GASOLINE INJECTION (MOTRONIC TYPE)

In the central injection system, the mixture is supplied and distributed among the cylinders inside the intake manifold (Fig. 2.64).

The most modern system of distributed fuel injection is distinguished by the fact that a separate nozzle is installed in the intake tract of each cylinder, which at a certain moment injects a metered portion of gasoline onto the intake valve of the corresponding cylinder. Gasoline received

into the cylinder, evaporates and mixes with air, forming a combustible mixture. Engines with such power supply systems have better fuel efficiency and a lower content of harmful substances in exhaust gases compared to carburetor engines.

The operation of the injectors is controlled by an electronic control unit (ECU) (Fig. 2.63), which is a special computer that receives and processes electrical signals from a system of sensors, compares their readings with the values

stored in the computer memory, and generates electrical control signals to the injector solenoid valves and other actuators. In addition, the ECU constantly carries out diagnostics

Rice. 2.65. Scheme of the Motronic distributed fuel injection system: 1 - fuel supply; 2 - air supply; 3 - throttle valve; 4 - inlet pipeline; 5 - nozzles; 6 - engine

The fuel injection system also warns the driver in the event of a malfunction with the help of a warning lamp installed in the instrument panel. Serious faults are recorded in the memory of the control unit and can be read out during diagnostics.

The power supply system with distributed injection has the following components:

Fuel supply and purification system;

Air supply and purification system;

Gasoline vapor capture and combustion system;

Electronic part with a set of sensors;

Exhaust gas exhaust and afterburning system.

Fuel supply system consists of a fuel tank, an electric fuel pump, a fuel filter, pipelines and a fuel rail, on which nozzles and a fuel pressure regulator are installed.

Rice. 2.66. Submersible electric fuel pump; a - fuel intake with pump; b - the appearance of the pump and the pump section of the rotary type fuel pump with an electric drive; in - gear; g - roller; d - lamellar; e - scheme of operation of the pump section of the rotary type: 1 - housing; 2 - suction zone; 3 - rotor; 4 - injection zone; 5 - direction of rotation

Rice. 2.67. Fuel rail of a five-cylinder engine with nozzles installed on it, a pressure regulator and a fitting for pressure control

Electric fuel pump(usually roller) can be installed both inside the gas tank (Fig. 2.66) and outside. The fuel pump is switched on by an electromagnetic relay. Gasoline is sucked by the pump from the tank and at the same time washes and cools the pump motor. At the outlet of the pump there is a check valve that does not allow fuel to flow out of the pressure line when the fuel pump is turned off. A safety valve is used to limit the pressure.

The fuel coming from the gasoline pump, under a pressure of at least 280 kPa, passes through fuel filter fine cleaning and enters the fuel rail. The filter has a metal housing filled with a paper filter element.

Ramp(Fig. 2.67) is a hollow structure to which nozzles and a pressure regulator are attached. The ramp is bolted to the engine intake manifold. A fitting is also installed on the ramp, which serves to control fuel pressure. The fitting is closed with a screw plug to protect it from contamination.

Nozzle(Fig. 2.68) has a metal case, inside which is located solenoid valve, consisting of an electrical winding, a steel core, a spring and a locking needle. At the top of the nozzle there is a small mesh filter that protects the nozzle nozzle (which has very small holes) from contamination. Rubber rings provide the necessary seal between the rail, nozzle and seat in the inlet pipeline. Nozzle fixation

on the ramp is carried out using a special clamp. On the body of the nozzle there are electrical contacts for

Rice. 2.68. Gasoline engine solenoid injectors: left - GM, right - Bosch

Rice. 2.69. Fuel pressure control: 1 - body; 2 - cover; 3 - a branch pipe for a vacuum hose; 4 - membrane; 5 - valve; A - fuel cavity; B - vacuum cavity

Rice. 2.70. Plastic intake pipe with reservoir and throttle connection

electrical connector switch. The regulation of the amount of fuel injected by the injector is carried out by changing the length of the electrical pulse applied to the injector contacts.

pressure regulator fuel (Fig. 2.69) serves to change the pressure in the rail, depending on the vacuum in the intake pipeline. The steel body of the regulator contains a spring-loaded needle valve connected to the diaphragm. The diaphragm, on the one hand, is affected by the fuel pressure in the rail, and on the other hand, by the vacuum in the intake manifold. With an increase in vacuum, while closing the throttle, the valve opens, excess fuel is drained through the drain pipe back into the tank, and the pressure in the rail decreases.

Recently, injection systems have appeared in which there is no fuel pressure regulator. For example, on a V8 engine ramp car New range rover there is no pressure regulator, and the composition of the combustible mixture is provided only by the operation of the nozzles that receive signals from the electronic unit.

Air supply and purification system consists of an air filter with a replaceable filter element, a throttle connection with a damper and a regulator idle move, receiver faith and exhaust pipeline (Fig. 2.70).

Receiver must have a sufficiently large volume in order to smooth out the pulsations of the air entering the engine cylinders.

Throttle pipe fixed on the receiver and serves to change the amount of air entering the engine cylinders. The change in the amount of air is carried out with the help of a throttle valve, rotated in the housing with the help of a cable drive from the “gas” pedal. Throttle position sensor and idle speed control are installed on the throttle pipe. The throttle pipe has openings for vacuum intake, which is used by the gasoline vapor recovery system.

Recently, designers of injection systems have begun to use an electric control drive when there is no mechanical connection between the “gas” pedal and the throttle valve (Fig. 2.71). In such designs, sensors of its position are installed on the “gas” pedal, and the throttle valve is rotated by a stepper motor with a gearbox. The electric motor turns the damper according to the signals of the computer that controls the operation of the motor. In such designs, not only the precise execution of the driver's commands is ensured, but it is also possible to influence the operation of the engine, correcting driver errors, by the operation of electronic systems for maintaining vehicle stability and other modern electronic security systems.

Rice. 2.71. Throttle valve with electric Rice. 2.72. Inductive sensors with a posi- tive drive provides crankshaft and distribu- tion control of the engine through dips

Waters

Throttle position sensor is a potentiometer whose slider is connected to the throttle axis. When the throttle is turned, the electrical resistance of the sensor and its supply voltage change, which is the output signal for the ECU. Motorized throttle control systems use at least two sensors to allow the computer to determine the direction in which the throttle is moving.

idle speed controller serves to adjust the engine idle speed by changing the amount of air passing around the closed throttle valve. The regulator consists of a stepper motor controlled by an ECU and a cone valve. In modern systems with more powerful engine control computers, idle controllers are dispensed with. The computer, analyzing the signals from numerous sensors, controls the duration of the electric current pulses supplied to the injectors and the operation of the engine in all modes, including idling.

Between air filter and the inlet pipe fitting is installed fuel mass flow sensor. The sensor changes the frequency of the electrical signal to the computer, depending on the amount of air passing through the pipe. From this sensor comes to the ECU and an electrical signal corresponding to the temperature of the incoming air. The first electronic injection systems used sensors that estimated the volume of incoming air. A damper was installed in the inlet pipe, which deviated by a different amount depending on the pressure of the incoming air. A potentiometer was connected to the damper, which changed the resistance depending on the amount of damper rotation. Modern mass air flow sensors operate using the principle of changing the electrical resistance of a heated wire or conductive film when it is cooled by an incoming air stream. The control computer, which also receives signals from the intake air temperature sensor, can determine the amount of air entering the engine.

For the correct control of the operation of the distributed injection system, the electronic unit requires signals from other sensors. The latter include: coolant temperature sensor, crankshaft position and speed sensor, vehicle speed sensor, knock sensor, oxygen concentration sensor (installed in the exhaust pipe of the exhaust system in the version of the feedback injection system).

At present, semiconductors are mainly used as temperature sensors, which change the electrical resistance with a change in temperature. The position and speed sensors of the crankshaft are usually of the inductive type (Fig. 2.72). They give out pulses of electric current when the flywheel with marks on it rotates.

Rice. 2.73. Scheme of the adsorber: 1 - intake air; 2 - throttle valve; 3 - intake manifold of the engine; 4 - purge valve of the vessel with activated carbon; 5 - signal from ECU; 6 - a vessel with activated carbon; 7 - ambient air; 8 - fuel vapor in the fuel tank

The power supply system with distributed injection can be sequential or parallel. In a parallel injection system, depending on the number of engine cylinders, several injectors fire simultaneously. In a sequential injection system, only one specific injector fires at the right time. In the second case, the ECU must receive information about the moment each piston is near TDC in the intake stroke. This requires not only a crankshaft position sensor, but also position sensor camshaft. On the modern cars, as a rule, engines with sequential injection are installed.

For catching gasoline vapors, which evaporates from the fuel tank, special adsorbers with activated carbon are used in all injection systems (Fig. 2.73). Activated carbon, located in a special container connected by a pipeline to fuel tank absorbs gasoline vapors well. To remove gasoline from the adsorber, the latter is purged with air and connected to the engine intake pipe, in order to

so that the operation of the engine is not disturbed, purge is carried out only at certain engine operating modes, with the help of special valves, which open and close at the command of the ECU.

Feedback injection systems use oxygen concentration sensors yes in exhaust gases that are installed in the exhaust system with an exhaust gas catalytic converter.

catalytic converter(Fig. 2.74;

Rice. 2.74. Two-layer three-way catalytic converter for exhaust gases: 1 - oxygen concentration sensor for a closed control loop; 2 - monolithic carrier block; 3 - mounting element in the form of a wire mesh; 4 - double-shell thermal insulation of the neutralizer

2.75) is installed in the exhaust system to reduce the content of harmful substances in the exhaust gases. The neutralizer contains one reducing (rhodium) and two oxidizing (platinum and palladium) catalysts. Oxidation catalysts promote the oxidation of unburned hydrocarbons (CH) into water vapour,

Rice. 2.75. The appearance of the neutralizer

and carbon monoxide (CO) into carbon dioxide. The reduction catalyst reduces harmful nitrogen oxides NOx into harmless nitrogen. Since these converters reduce the content of three harmful substances in the exhaust gases, they are called three-component.

The operation of a car engine on leaded gasoline leads to the failure of an expensive catalytic converter. Therefore, the use of leaded gasoline is prohibited in most countries.

A three-way catalytic converter works most efficiently when a stoichiometric mixture is supplied to the engine, i.e. with an air-fuel ratio of 14.7:1 or an excess air ratio of one. If there is too little air in the mixture (i.e. not enough oxygen), then CH and CO will not completely oxidize (burn) to a safe by-product. If there is too much air, then the decomposition of NOX into oxygen and nitrogen cannot be ensured. Therefore, a new generation of engines appeared, in which the composition of the mixture was constantly adjusted to obtain an exact correspondence to the excess air ratio cc = 1 using an oxygen concentration sensor (lambda probe yes) (Fig. 2.77), built into the exhaust system.

Rice. 2.76. Dependence of the efficiency of the neutralizer on the coefficient of excess air

Rice. 2.77. Oxygen concentration sensor device: 1 - sealing ring; 2 - metal case with thread and turnkey hexagon; 3 - ceramic insulator; 4 - wires; 5 - sealing cuff of wires; 6 - current-carrying contact of the heater power wire; 7 - external protective screen with an opening for atmospheric air; 8 - current pickup of electrical signal; 9 - electric heater; 10 - ceramic tip; 11 - protective screen with a hole for exhaust gases

This sensor detects the amount of oxygen in the exhaust gases, and its electrical signal is used by the ECU, which changes the amount of fuel injected accordingly. The principle of operation of the sensor is the ability to pass oxygen ions through itself. If the oxygen content on the active surfaces of the sensor (one of which is in contact with the atmosphere, and the other with the exhaust gases) differs significantly, there is a sharp change in the voltage at the sensor outputs. Sometimes two oxygen concentration sensors are installed: one before the converter, and the other after.

In order for the catalyst and the oxygen concentration sensor to work effectively, they must be heated to a certain temperature. The minimum temperature at which 90% of harmful substances are retained is about 300 °C. It is also necessary to avoid overheating of the converter, as this can lead to damage to the filler and partially block the passage for gases. If the engine starts to work intermittently, then the unburned fuel burns out in the catalyst, sharply increasing its temperature. Sometimes a few minutes of intermittent operation of the engine can be enough to completely damage the catalytic converter. This is why the electronic systems of modern engines must detect and prevent misfiring and warn the driver of the severity of the problem. Sometimes electric heaters are used to speed up the warming up of the catalytic converter after starting a cold engine. Oxygen concentration sensors currently in use almost all have heating elements. IN modern engines, in order to limit emissions of harmful substances into the atmosphere

ru during engine warm-up, pre-catalytic converters are installed as close as possible to the exhaust manifold (Fig. 2.78) in order to ensure quick heating of the converter to operating temperature. oxygen sensors installed before and after the converter.

To improve the environmental performance of the engine, it is necessary not only to improve the exhaust gas converters, but also to improve the processes occurring in the engine. The content of hydrocarbons became possible to reduce by reducing

"gap volumes", such as the gap between the piston and the cylinder wall above the top compression ring, and cavities around the valve seats.

A thorough study of the flow of the combustible mixture inside the cylinder using computer technology made it possible to provide more complete combustion and low CO levels. The NOx level has been reduced by the EGR system by taking some of the gas from the exhaust system and feeding it into the intake air stream. These measures and fast, precise control of engine transients can keep emissions to a minimum even before the catalyst. To accelerate the heating of the catalytic converter and its entry into the operating mode, the method of secondary air supply to the exhaust manifold using a special electric pump is also used.

Another effective and widespread method of neutralizing harmful products in exhaust gases is flame afterburning, which is based on the ability of combustible components of exhaust gases (CO, CH, aldehydes) to oxidize at high temperatures. The exhaust gases enter the afterburner chamber, which has an ejector through which heated air enters from the heat exchanger. The combustion takes place in the chamber,

Rice. 2.78. Engine exhaust manifold and for ignition is the ignition

with pre-neutralizer candle.

DIRECT GASOLINE INJECTION

The first gasoline injection systems directly into the engine cylinders appeared in the first half of the 20th century. and used on aircraft engines. Attempts to use direct injection in gasoline car engines were discontinued in the 40s of the 19th century, because such engines turned out to be expensive, uneconomical and smoked heavily in modes high power. Injecting gasoline directly into the cylinders is associated with certain difficulties. Gasoline direct injection injectors operate under more difficult conditions than those installed in the intake manifold. The head of the block, in which such nozzles must be installed, turns out to be more complex and expensive. The time allotted for the carburetion process with direct injection is significantly reduced, which means that for good carburetion it is necessary to supply gasoline under high pressure.

Mitsubishi specialists managed to cope with all these difficulties, which for the first time applied the gasoline direct injection system to automotive engines. First production car Mitsubishi Galant with 1.8 GDI engine (Gasoline direct injection- direct injection of gasoline) appeared in 1996 (Fig. 2.81). Now engines with direct gasoline injection are produced by Peugeot-Citroen, Renault, Toyota, DaimlerChrysler and other manufacturers (Fig. 2.79; 2.80; 2.84).

The benefits of the direct injection system are mainly in improved fuel economy, but also some increase in power. The first is due to the ability of a direct injection engine to operate

Rice. 2.79. Scheme Volkswagen engine FSI direct injection

Rice. 2.80. In 2000, PSA Peugeot-Citroen introduced its 2.0-litre, four-cylinder HPI direct injection engine that could run on lean mixtures.

on very lean mixtures. The increase in power is mainly due to the fact that the organization of the process of supplying fuel to the engine cylinders makes it possible to increase the compression ratio to 12.5 (in conventional gasoline engines, it is rarely possible to set the compression ratio above 10 due to detonation).

In the GDI engine, the fuel pump provides a pressure of 5 MPa. An electro-magnetic injector installed in the cylinder head injects gasoline directly into the engine cylinder and can operate in two modes. Depending on the supplied electrical signal, it can inject fuel either with a powerful conical torch or with a compact jet (Fig. 2.82). The bottom of the piston has a special shape in the form of a spherical recess (Fig. 2.83). This shape allows the incoming air to be swirled, directing the injected fuel to a spark plug mounted in the center of the combustion chamber. The inlet pipe is not located on the side, but vertical

Rice. 2.81. Mitsubishi GDI engine - the first mass-produced engine with a gasoline direct injection system

but on top. It does not have sharp bends, and therefore the air enters at a high speed.

Rice. 2.82. The GDI engine injector can operate in two modes, providing a powerful (a) or compact (b) atomized gasoline jet

In the operation of an engine with a direct injection system, three different modes can be distinguished:

1) mode of operation on super-poor mixtures;

2) operating mode on a stoichiometric mixture;

3) the mode of sharp accelerations from low speeds;

First mode is used when the car is moving without sudden accelerations at a speed of about 100-120 km/h. This mode uses a very lean combustible mixture with an excess air ratio of more than 2.7. Under normal conditions, such a mixture cannot be ignited by a spark, so the injector injects fuel in a compact flame at the end of the compression stroke (as in a diesel engine). The spherical recess in the piston directs the jet of fuel to the spark plug electrodes, where the high concentration of gasoline vapor allows the mixture to ignite.

Second mode used when the car is moving at high speed and when sharp accelerations when high power is needed. Such a mode of motion requires a stoichiometric composition of the mixture. A mixture of this composition is highly flammable, but the GDI engine has an increased degree of

compression, and in order to prevent detonation, the nozzle injects fuel with a powerful torch. The finely atomized fuel fills the cylinder and, as it evaporates, cools the cylinder surfaces, reducing the likelihood of detonation.

Third mode necessary to obtain a large torque when the gas pedal is pressed sharply when the engine is running

runs at low speeds. This mode of engine operation differs in that the injector fires twice during one cycle. During the intake stroke to the cylinder for

Rice. 2.83. The piston of an engine with gasoline direct injection has a special shape (combustion process above the piston)

4. Order No. 1031. 97

Rice. 2.84. Design features Audi 2.0 FSI direct injection engine

cooling it with a powerful torch, an extra-poor mixture (a = 4.1) is injected. At the end of the compression stroke, the injector injects fuel again, but with a compact flame. In this case, the mixture in the cylinder is enriched and detonation does not occur.

Compared to a conventional gasoline port injection engine, a GDI engine is about 10% more economical and emits 20% less carbon dioxide into the atmosphere. The increase in engine power is up to 10%. However, as the operation of vehicles with engines of this type has shown, they are very sensitive to the sulfur content in gasoline.

The original gasoline direct injection process was developed by Orbital. In this process, gasoline is injected into the engine cylinders, pre-mixed with air using a special nozzle. The Orbital nozzle consists of two jets, fuel and air.

Rice. 2.85. Orbital nozzle operation

Air is supplied to the air jets in compressed form from a special compressor at a pressure of 0.65 MPa. The fuel pressure is 0.8 MPa. First, the fuel jet fires, and then the air jet at the right time, so the fuel-air mixture in the form of an aerosol is injected into the cylinder with a powerful torch (Fig. 2.85).

An injector, located in the cylinder head next to the spark plug, injects a fuel-air jet directly onto the spark plug electrodes, which ensures good spark plug ignition.

In the late 60s and early 70s of the XX century, the problem of environmental pollution by industrial waste arose, among which a significant part was car exhaust gases. Until that time, the composition of the combustion products of internal combustion engines was of no interest to anyone. In order to maximize the use of air in the combustion process and achieve maximum possible power engine, the composition of the mixture was regulated in such a way that it contained an excess of gasoline.

As a result, oxygen was completely absent in the combustion products, but unburned fuel remained, and substances harmful to health are formed mainly during incomplete combustion. In an effort to increase power, designers installed accelerator pumps on carburetors that inject fuel into the intake manifold with each sharp press on the accelerator pedal, i.e. when you need a sharp acceleration of the car. In this case, an excessive amount of fuel enters the cylinders, which does not correspond to the amount of air.

In urban traffic, the accelerator pump works at almost all intersections with traffic lights, where cars must either stop or move quickly. Incomplete combustion also occurs when the engine is running at idling especially during engine braking. When the throttle is closed, air flows through the carburetor idle passages at high speed, sucking in too much fuel.

Due to the significant underpressure in the intake manifold, little air is sucked into the cylinders, the pressure in the combustion chamber remains relatively low at the end of the compression stroke, the combustion process is excessive rich mixture passes slowly, and a lot of unburned fuel remains in the exhaust gases. The described engine operation modes sharply increase the content of toxic compounds in combustion products.

It became obvious that in order to reduce harmful emissions into the atmosphere for human life, it is necessary to radically change the approach to the design of fuel equipment.

To reduce harmful emissions into the exhaust system, it was proposed to install an exhaust gas catalytic converter. But the catalyst works effectively only when the so-called normal fuel-air mixture is burned in the engine (weight ratio air / gasoline 14.7: 1). Any deviation of the composition of the mixture from the specified one led to a drop in the efficiency of its work and accelerated failure. For stable maintenance of such a ratio of the working mixture, carburetor systems were no longer suitable. Only injection systems could become an alternative.

The first systems were purely mechanical with little use of electronic components. But the practice of using these systems has shown that the parameters of the mixture, the stability of which the developers counted on, change as the car is used. This result is quite natural, taking into account the wear and contamination of the elements of the system and the internal combustion engine itself during its service life. The question arose about a system that could correct itself in the process of work, flexibly shifting the conditions for preparing the working mixture depending on external conditions.

The way out was found next. Feedback was introduced into the injection system - in the exhaust system, directly in front of the catalyst, they put an oxygen content sensor in the exhaust gases, the so-called lambda probe. This system was developed already taking into account the presence of such an element fundamental for all subsequent systems as an electronic control unit (ECU). According to the signals from the oxygen sensor, the ECU adjusts the fuel supply to the engine, accurately maintaining the desired mixture composition.

To date, the injection (or, in Russian, injection) engine has almost completely replaced the outdated
carburetor system. The injection engine significantly improves the performance and power performance of the car
(acceleration dynamics, environmental characteristics, fuel consumption).

Fuel injection systems have the following main advantages over carburetor systems:

• accurate dosing of fuel and, consequently, more economical fuel consumption.
• toxicity reduction exhaust gases. It is achieved due to the optimality of the fuel-air mixture and the use of exhaust gas parameters sensors.
• increase in engine power by about 7-10%. Occurs due to improved filling of cylinders, optimal setting of the ignition timing corresponding to the operating mode of the engine.
• improvement of the dynamic properties of the car. The injection system immediately responds to any load changes by adjusting the parameters of the fuel-air mixture.
• ease of starting regardless of weather conditions.

Device and principle of operation (on the example of an electronic system of distributed injection)

In modern injection engines, an individual nozzle is provided for each cylinder. All injectors are connected to the fuel rail, where the fuel is under pressure, which creates an electric fuel pump. The amount of injected fuel depends on the duration of the injector opening. The moment of opening is regulated by the electronic control unit (controller) based on the data it processes from various sensors.

The mass air flow sensor is used to calculate the cyclic filling of the cylinders. The mass air flow is measured, which is then recalculated by the program into cylinder cyclic filling. In the event of a sensor failure, its readings are ignored, the calculation is based on emergency tables.

The throttle position sensor is used to calculate the load factor on the engine and its changes depending on the throttle opening angle, engine speed and cyclic filling.

The coolant temperature sensor is used to determine the correction of fuel supply and ignition by temperature and to control the electric fan. In the event of a sensor failure, its readings are ignored, the temperature is taken from the table depending on the engine operating time.

The crankshaft position sensor is used for general synchronization of the system, calculation of engine speed and crankshaft position at certain points in time. DPKV - polar sensor. If turned on incorrectly, the engine will not start. If the sensor fails, the operation of the system is impossible. This is the only "vital" sensor in the system, in which the movement of the car is impossible. Accidents of all other sensors allow you to get to the car service on your own.

The oxygen sensor is designed to determine the oxygen concentration in the exhaust gases. The information provided by the sensor is used by the electronic control unit to adjust the amount of fuel supplied. The oxygen sensor is used only in systems with a catalytic converter for Euro-2 and Euro-3 toxicity standards (Euro-3 uses two oxygen sensors - before and after the catalyst).

The knock sensor is used to control knocking. When the latter is detected, the ECU turns on the detonation damping algorithm, quickly adjusting the ignition timing.

Listed here are just some of the main sensors required for the system to function. Complete set of sensors for various cars depend on the injection system, on toxicity standards, etc.

Based on the results of a survey of the sensors defined in the program, the ECU program controls the actuators, which include: injectors, a gasoline pump, an ignition module, an idle speed controller, an adsorber valve for a gasoline vapor recovery system, a cooling system fan, etc. (again, everything depends on the specific models)

Of all the above, perhaps not everyone knows what an adsorber is. The adsorber is an element of a closed circuit for the recirculation of gasoline vapors. Euro-2 standards prohibit the contact of the ventilation of the gas tank with the atmosphere, gasoline vapors must be collected (adsorbed) and sent to the cylinders for afterburning when purged. When the engine is not running, gasoline vapors enter the adsorber from the tank and intake manifold, where they are absorbed. When the engine is started, the adsorber, at the command of the ECU, is purged with a stream of air drawn in by the engine, the vapors are carried away by this stream and burnt out in the combustion chamber.

Types of fuel injection systems

Depending on the number of nozzles and the place of fuel supply, injection systems are divided into three types: single-point or mono-injection (one nozzle per intake manifold to all cylinders), multi-point or distributed (each cylinder has its own injector that supplies fuel to the manifold) and direct (fuel is supplied by injectors directly to the cylinders, like diesel engines).

single point injection simpler, it is less stuffed with control electronics, but also less efficient. The control electronics allows you to take information from the sensors and immediately change the injection parameters. It is also important that carburetor engines are easily adapted for mono-injection with almost no structural alterations or technological changes in production. Single-point injection has an advantage over a carburetor in terms of fuel economy, environmental friendliness and relative stability and reliability of parameters. But in the throttle response of the engine, single-point injection loses. Another disadvantage: when using a single-point injection, as well as when using a carburetor, up to 30% of gasoline settles on the walls of the manifold.

Single-point injection systems, of course, were a step forward compared to carburetor power systems, but no longer meet modern requirements.

The systems are more advanced multipoint injection, in which the fuel supply to each cylinder is carried out individually. Distributed injection is more powerful, more economical and more complex. The use of such injection increases engine power by about 7-10 percent. The main advantages of distributed injection:

• the ability to automatically adjust at different speeds and, accordingly, improve the filling of the cylinders, as a result, with the same maximum power, the car accelerates much faster;
• gasoline is injected near the intake valve, which significantly reduces the loss of sedimentation in the intake manifold and allows for more precise adjustment of the fuel supply.

As another and effective tool in optimizing the combustion of the mixture and increasing the efficiency of a gasoline engine, it implements simple
principles. Namely: it sprays fuel more thoroughly, mixes it better with air and more competently disposes of the finished mixture in different engine operating modes. As a result, direct injection engines consume less fuel than conventional "injection" engines (especially when quiet ride at low speed) with the same working volume, they provide more intensive acceleration of the car; they have cleaner exhaust; they guarantee higher liter output due to the higher compression ratio and the effect of cooling the air when the fuel evaporates in the cylinders. At the same time, they need quality gasoline with a low content of sulfur and mechanical impurities to ensure the normal operation of the fuel equipment.

And just the main discrepancy between GOSTs, currently in force in Russia and Ukraine, and European standards is the increased content of sulfur, aromatic hydrocarbons and benzene. For example, the Russian-Ukrainian standard allows for the presence of 500 mg of sulfur in 1 kg of fuel, while Euro-3 - 150 mg, Euro-4 - only 50 mg, and Euro-5 - only 10 mg. Sulfur and water can activate corrosion processes on the surface of parts, and debris is a source of abrasive wear of the calibrated nozzle holes and plunger pairs of pumps. As a result, wear is reduced operating pressure pump and the quality of gasoline spraying deteriorates. All this is reflected in the characteristics of the engines and the uniformity of their work.

Mitsubishi was the first to use a direct injection engine in a production car. Therefore, we will consider the device and principles of operation of direct injection using the example of a GDI (Gasoline Direct Injection) engine. The GDI engine can operate in ultra-lean air-fuel mixture combustion mode: the ratio of air and fuel by weight is up to 30-40:1.

The maximum possible ratio for traditional injection engines with distributed injection is 20-24: 1 (it is worth recalling that the optimal, so-called stoichiometric, composition is 14.7: 1) - if there is more excess air, the lean mixture simply will not ignite. On a GDI engine, the atomized fuel is in the cylinder in the form of a cloud concentrated around the spark plug.

Therefore, although the mixture is over-lean in general, it is close to the stoichiometric composition at the spark plug and is easily ignited. At the same time, the lean mixture in the rest of the volume has a much lower tendency to detonate than the stoichiometric one. The latter circumstance allows you to increase the compression ratio, and therefore increase both power and torque. Due to the fact that when the fuel is injected and evaporated into the cylinder, the air charge is cooled - the filling of the cylinders improves somewhat, and the likelihood of detonation again decreases.

The main design differences between GDI and conventional injection:

High pressure fuel pump (TNVD). A mechanical pump (similar to the injection pump of a diesel engine) develops a pressure of 50 bar (in an injection engine, an electric pump in the tank creates a pressure of about 3-3.5 bar in the line).

• High-pressure nozzles with swirl atomizers create the shape of the fuel jet, in accordance with the engine operating mode. In the power mode of operation, injection occurs in the intake mode and a conical air-fuel jet is formed. In the ultra-lean mixture mode, injection occurs at the end of the compression stroke and a compact air-fuel is formed.
  a torch that the concave piston crown sends directly to the spark plug.
• Piston. A recess is made in the bottom of a special shape, with the help of which the fuel-air mixture is directed to the area of ​​​​the spark plug.
• inlet channels. On the GDI engine, vertical intake channels are used, which ensure the formation of the so-called in the cylinder. “reverse vortex”, directing the air-fuel mixture to the candle and improving the filling of the cylinders with air (in a conventional engine, the vortex in the cylinder is twisted in the opposite direction).

GDI engine operating modes

In total, there are three modes of engine operation:

• Super-lean combustion mode (fuel injection on the compression stroke).
• Power mode (injection on the intake stroke).
• Two-stage mode (injection on the intake and compression strokes) (used on euro modifications).

Super-lean combustion mode(fuel injection on the compression stroke). This mode is used for light loads: for quiet city driving and when driving outside the city at a constant speed (up to 120 km/h). Fuel is injected in a compact jet at the end of the compression stroke towards the piston, bounces off the piston, mixes with air and vaporizes towards the spark plug area. Although the mixture in the main volume of the combustion chamber is extremely lean, the charge in the region of the candle is rich enough to be ignited by a spark and ignite the rest of the mixture. As a result, the engine runs steadily even at a total cylinder air/fuel ratio of 40:1.

The operation of the engine on a very lean mixture set new problem– neutralization of the fulfilled gases. The fact is that in this mode, their main share is nitrogen oxides, and therefore a conventional catalytic converter becomes ineffective. To solve this problem, exhaust gas recirculation (EGR-Exhaust Gas Recirculation) was applied, which dramatically reduces the amount of nitrogen oxides formed, and an additional NO-catalyst was installed.

The EGR system, by “diluting” the fuel-air mixture with exhaust gases, lowers the combustion temperature in the combustion chamber, thereby “muffling” the active formation of harmful oxides, including NOx. However, it is impossible to ensure complete and stable NOx neutralization only due to EGR, since with an increase in engine load, the amount of bypassed exhaust gas must be reduced. Therefore, an NO-catalyst was introduced to the engine with direct injection.

There are two types of catalysts for reducing NOx emissions - selective (Selective Reduction Type) and
storage type (NOx Trap Type). Storage type catalysts are more efficient, but are extremely sensitive to high sulfur fuels, which is less susceptible to selective ones. In accordance with this, storage catalysts are installed on models for countries with low sulfur content in gasoline, and selective - for the rest.

Power mode(injection on the intake stroke). The so-called "homogeneous mixture mode" is used for intensive urban driving, high-speed suburban traffic and overtaking. The fuel is injected on the intake stroke with a conical torch, mixing with air and forming a homogeneous mixture, as in a conventional port injection engine. The composition of the mixture is close to stoichiometric (14.7:1)

Two stage mode(injection on the intake and compression strokes). This mode allows you to increase the engine torque when the driver, moving at low speeds, sharply presses the accelerator pedal. When the engine is running at low speeds, and a rich mixture is suddenly supplied to it, the likelihood of detonation increases. Therefore, the injection is carried out in two stages. A small amount of fuel is injected into the cylinder during the intake stroke and cools the air in the cylinder. In this case, the cylinder is filled with an ultra-poor mixture (approximately 60:1), in which detonation processes do not occur. Then, at the end of the bar
compression, a compact jet of fuel is delivered that brings the air-to-fuel ratio in the cylinder to a “rich” 12:1.

Why is this mode introduced only for cars for the European market? Yes, because Japan is characterized by low speeds and constant traffic jams, while Europe is characterized by long autobahns and high speeds (and, consequently, high engine loads).

Mitsubishi has pioneered the use of direct fuel injection. To date, Mercedes (CGI), BMW (HPI), Volkswagen (FSI, TFSI, TSI) and Toyota (JIS) use similar technology. The main principle of operation of these power systems is similar - the supply of gasoline not to the intake tract, but directly to the combustion chamber and the formation of layered or homogeneous mixture formation in various engine operating modes. But such fuel systems also have differences, and sometimes quite significant ones. The main ones are the working pressure in the fuel system, the location of the nozzles and their design.

The main purpose of the injection system (another name is the injection system) is to ensure the timely supply of fuel to the working cylinders of the internal combustion engine.

Currently, such a system is actively used on diesel and gasoline internal combustion engines. It is important to understand that for each type of engine the injection system will be significantly different.

Photo: rsbp (flickr.com/photos/rsbp/)

So in gasoline internal combustion engines, the injection process contributes to the formation of an air-fuel mixture, after which it is forced to ignite from a spark.

In diesel internal combustion engines, the fuel supply is carried out under high pressure, when one part of the fuel mixture is combined with hot compressed air and spontaneously ignites almost instantly.

The injection system remains a key part of the overall fuel system of any vehicle. The central working element of such a system is the fuel injector (injector).

As mentioned earlier, various types of injection systems are used in gasoline engines and diesel engines, which we will review in an overview in this article, and will analyze in detail in subsequent publications.

Types of injection systems on gasoline ICEs

On gasoline engines, the following fuel supply systems are used - central injection (mono injection), distributed injection (multipoint), combined injection and direct injection.

central injection

The fuel supply in the central injection system occurs due to the fuel injector, which is located in the intake manifold. Since there is only one nozzle, this injection system is also called monoinjection.

Systems of this type have lost their relevance today, therefore they are not provided for in new car models, however, they can be found in some old models of some car brands.

The advantages of mono injection include reliability and ease of use. The disadvantages of such a system are the low level of environmental friendliness of the engine and high fuel consumption.

Distributed injection

The multi-point injection system provides for the supply of fuel separately to each cylinder, equipped with its own fuel injector. In this case, fuel assemblies are formed only in the intake manifold.

Currently, most gasoline engines are equipped with a distributed fuel supply system. The advantages of such a system are high environmental friendliness, optimal fuel consumption, and moderate requirements for the quality of consumed fuel.

direct injection

One of the most advanced and progressive injection systems. The principle of operation of such a system is the direct supply (injection) of fuel into the combustion chamber of the cylinders.

The direct fuel supply system makes it possible to obtain a high-quality composition of fuel assemblies at all stages ICE operation in order to improve the process of combustion of the combustible mixture, increase the working power of the engine, reduce the level of exhaust gases.

The disadvantages of this injection system include a complex design and high requirements for fuel quality.

Combined injection

This type of system combines two systems - direct and distributed injection. Often it is used to reduce emissions of toxic elements and exhaust gases, thereby achieving high environmental performance of the engine.

All fuel supply systems used on gasoline ICEs can be equipped with mechanical or electronic control devices, of which the latter is the most advanced, since it provides the best performance in terms of economy and environmental friendliness of the engine.

Fuel supply in such systems can be carried out continuously or discretely (pulse). According to experts, pulsed fuel supply is the most appropriate and efficient and is currently used in all modern engines.

Types of injection systems for diesel internal combustion engines

On modern diesel engines injection systems such as a pump-injector system, a common rail system, a system with an in-line or distribution injection pump (high pressure fuel pump) are used.

The most popular and considered the most progressive of them are the systems: Common Rail and pump injectors, which we will discuss in more detail below.

The injection pump is the heart of any diesel fuel system.

In diesel engines, the combustible mixture can be supplied both to the preliminary chamber and directly to the combustion chamber (direct injection).

To date, preference is given to the direct injection system, which is distinguished by elevated level noise and less smooth operation of the engine, compared with injection into the preliminary chamber, but at the same time a much more important indicator is provided - efficiency.

Pump-injector injection system

A similar system is used for supplying and injecting a fuel mixture under high pressure by a central device - pump injectors.

By the name, you can guess that the key feature of this system is that in a single device (pump-injector) two functions are combined at once: pressure generation and injection.

The design disadvantage of this system is that the pump is equipped with a constant-type drive from the engine camshaft (not switched off), which leads to rapid wear of the structure. Because of this, manufacturers are increasingly opting for a common rail injection system.

Common rail injection system (accumulator injection)

This is a more advanced TC supply system for most diesel engines. Its name comes from the main structural element - the fuel rail, common to all injectors. Common Rail translated from English just means - a common ramp.

In such a system, fuel is supplied to the fuel injectors from a rail, which is also called a high-pressure accumulator, which is why the system has a second name - a battery injection system.

The Common Rail system provides for three stages of injection - preliminary, main and additional. This makes it possible to reduce the noise and vibrations of the engine, to make the process of self-ignition of fuel more efficient, and to reduce the amount of harmful emissions into the atmosphere.

To control injection systems on diesel engines, mechanical and electronic devices are provided. Systems on the mechanics allow you to control the working pressure, volume and timing of fuel injection. Electronic systems more effective management diesel engines in general.

Conceptually, internal combustion engines - gasoline and diesel are almost identical, but there are a number of distinctive features. One of the main ones is the different course of combustion processes in the cylinders. In a diesel engine, fuel ignites from exposure to high temperatures and pressure. But for this it is necessary that diesel fuel be supplied directly to the combustion chambers, not only at a strictly defined moment, but also under high pressure. And this is provided by injection systems of diesel engines.

The constant tightening of environmental standards, attempts to get more power output at lower fuel costs provide the emergence of more and more new design solutions in.

The principle of operation for all existing types of diesel injection is identical. The main batteries are the high pressure fuel pump (TNVD) and the nozzle. The task of the first component is to inject diesel fuel, due to which the pressure in the system increases significantly. The nozzle also provides fuel supply (in a compressed state) to the combustion chambers, while spraying it to ensure better mixture formation.

It should be noted that fuel pressure directly affects the quality of combustion of the mixture. The higher it is, the better the diesel fuel burns, providing more power output and less pollutants in the exhaust gases. And to obtain higher pressure indicators, a variety of design solutions were used, which led to the emergence of different types of diesel power systems. Moreover, all the changes concerned exclusively these two elements - high-pressure fuel pumps and nozzles. The rest of the components - the tank, fuel lines, filter elements, in fact, are identical in all available forms.

Types of diesel power systems

Diesel power plants can be equipped with an injection system:

• with in-line high pressure pump;
• with distribution type pumps;
• battery type (Common Rail).

With row pump

In-line injection pump for 8 nozzles

Initially, this system was completely mechanical, but later electromechanical elements began to be used in its design (concerns the regulators for changing the cyclic supply of diesel fuel).

The main feature of this system lies in the pump. In it, plunger pairs (precision elements that create pressure) each served their own nozzle (their number corresponded to the number of nozzles). Moreover, these pairs were placed in a row, hence the name.

The advantages of a system with an in-line pump include:

• Design reliability. The pump had a lubrication system, which provided the assembly with a large resource;
• Low sensitivity to fuel purity;
• Comparative simplicity and high maintainability;
• Large pump resource;
• Possibility of operation of the motor in case of failure of one section or nozzle.

But the disadvantages of such a system are more significant, which led to its gradual abandonment and preference for more modern ones. The negative aspects of such an injection are:

• Low speed and accuracy of fuel dosage. Mechanical design simply unable to provide it;
• Relatively low pressure generated;
• The task of the injection pump is not only to create fuel pressure, but also to adjust the cyclic flow and injection timing;
• The pressure generated is directly dependent on the revolutions of the crankshaft;
• Large dimensions and weight of the pump.

These shortcomings, and first of all - the low pressure created, led to the abandonment of this system, since it simply ceased to fit into environmental standards.

With distributed type pump

The injection pump of distributed injection has become the next stage in the development of power systems for diesel units.

Initially, such a system was also mechanical and differed from the one described above only in the design of the pump. But over time, a system was added to her device electronic control, which improved the injection adjustment process, which had a positive effect on the engine's efficiency indicators. For a certain period, such a system fit into environmental standards.

The peculiarity of this type of injection was that the designers abandoned the use of a multi-section pump design. Only one plunger pair began to be used in the high-pressure fuel pump, serving all available nozzles, the number of which varies from 2 to 6. To ensure fuel supply to all nozzles, the plunger performs not only translational movements, but also rotational ones, which ensure the distribution of diesel fuel.

High pressure fuel pump with distributed type pump

TO positive qualities such systems were:

• Small overall dimensions and weight of the pump;
• The best performance in fuel efficiency;
• The use of electronic control has increased the performance of the system.

The disadvantages of a system with a distributed type pump include:

• A small resource of a plunger pair;
• The lubrication of the constituent elements is carried out by fuel;
• The multifunctionality of the pump (in addition to creating pressure, it is also controlled by the flow and injection timing);
• If the pump failed, the system stopped working;
• Sensitivity to airing;
• Dependence of pressure on engine speed.

This type of injection is widely used in passenger cars and small commercial vehicles.

Injector pump

The peculiarity of this system lies in the fact that the nozzle and plunger pair are combined into a single design. The drive section of this fuel unit is carried out from the camshaft.

It is noteworthy that such a system can be either completely mechanical (injection is controlled by a rail and regulators) or electronic (solenoid valves are used).

Pump nozzle

A variation on this type of injection is the use of individual pumps. That is, each nozzle has its own section, driven from the camshaft. The section can be located directly in the cylinder head or be placed in a separate building. In this design, conventional hydraulic nozzles are used (that is, the system is mechanical). Unlike high-pressure fuel injection, the high-pressure lines are very short, which allowed a significant increase in pressure. But this design has not received much distribution.

The positive qualities of the power supply injectors include:

• Significant indicators of the created pressure (the highest among all used types of injection);
• Small metal construction;
• Accuracy of dosing and implementation of multiple injection (in nozzles with solenoid valves);
• Possibility of engine operation in case of failure of one of the injectors;
• Replacing a damaged element is not difficult.

But there are also disadvantages in this type of injection, including:

• Non-repairable pump injectors (in case of breakage, they need to be replaced);
• High sensitivity to fuel quality;
• The pressure generated depends on the engine speed.

Pump injectors are widely used in commercial and freight transport, as well as this technology was used by some manufacturers of passenger cars. Now it is not very often used due to the high cost of maintenance.

common rail

While it is the most perfect in terms of efficiency. It also fully complies with the latest environmental standards. Additional "advantages" include its applicability to any diesel engines, from passenger cars to marine vessels.

Common rail injection system

Its peculiarity lies in the fact that the multifunctionality of the injection pump is not required, and its task is only to pressurize, and not for each nozzle separately, but for a common line ( fuel rail), and already from it diesel fuel is supplied to the nozzles.

At the same time, the fuel pipelines between the pump, the rail and the injectors have a relatively short length, which made it possible to increase the generated pressure.

The work in this system is controlled by an electronic unit, which significantly increased the accuracy of dosage and the speed of the system.

Positive qualities of Common Rail:

• High dosing accuracy and use of multi-mode injection;
• Reliability of injection pump;
• There is no dependence of the pressure value on the engine speed.

The downsides of this system are:

• Sensitivity to fuel quality;
• Complex design of nozzles;
• System failure at the slightest pressure loss due to depressurization;
• The complexity of the design due to the presence of a number of additional elements.

Despite these shortcomings, automakers are increasingly choosing Common Rail over other types of injection systems.