On modern cars Various fuel injection systems are used. The injection system (another name is the injection system, from injection) as the name suggests, provides fuel injection.

The injection system is used on both gasoline and diesel engines. At the same time, the designs and operation of injection systems for gasoline and diesel engines differ significantly.

In gasoline engines, injection produces a homogeneous fuel-air mixture, which is forcibly ignited by a spark. In diesel engines, fuel is injected under high pressure, a portion of the fuel is mixed with compressed (hot) air and ignites almost instantly. The injection pressure determines the amount of fuel injected and, accordingly, the engine power. Therefore, the higher the pressure, the higher the engine power.

The fuel injection system is an integral part of the vehicle's fuel system. The main working element of any injection system is the nozzle ( injector).

Gasoline engine injection systems

Depending on the method of formation of the fuel-air mixture, the following central injection systems are distinguished: distributed injection and direct injection. Central and distributed injection systems are pre-injection systems, i.e. injection into them is carried out before reaching the combustion chamber - in the intake manifold.

Diesel injection systems

Fuel injection in diesel engines can be done in two ways: into the preliminary chamber or directly into the combustion chamber.

Pre-chamber injection engines are characterized by low noise levels and smooth operation. But nowadays preference is given to direct injection systems. Despite increased level noise, such systems have high fuel efficiency.

The defining structural element of the diesel engine injection system is the high-pressure fuel pump (HPFP).

Passenger cars with a diesel engine are equipped with various designs of injection systems: with in-line injection pump, with distribution injection pump, pump injectors, Common Rail. Progressive injection systems - pump injectors and Common Rail system.

D. Sosnin

We are starting to publish articles on modern fuel injection systems for gasoline internal combustion engines of passenger cars.

1. Preliminary remarks

Fuel supply to gasoline engines in modern passenger cars is realized using injection systems. Based on their operating principle, these systems are usually divided into five main groups (Fig. 1): K, Mono, L, M, D.

2. Advantages of injection systems

The air-fuel mixture (FA mixture) is supplied from the carburetor to the cylinders of the internal combustion engine (ICE) through the long pipes of the intake manifold. The length of these pipes to different engine cylinders is not the same, and in the manifold itself there is uneven heating of the walls, even on a fully warmed-up engine (Fig. 2).

This leads to the fact that from the homogeneous TV mixture created in the carburetor, different cylinders ICE produces unequal fuel-air charges. As a result, the engine does not deliver the calculated power, the uniformity of torque, fuel consumption and the amount of harmful substances in the exhaust gases increase.

It is very difficult to combat this phenomenon in carburetor engines. It should also be noted that a modern carburetor operates on the principle of atomization, in which gasoline is atomized in a stream of air sucked into the cylinders. In this case, quite large drops of fuel are formed (Fig. 3, a),

This does not ensure high-quality mixing of gasoline and air. Poor mixing and large droplets make it easier for gasoline to settle on the walls of the intake manifold and on the walls of the cylinders during the absorption of the TV mixture. But when forced atomization of gasoline under pressure through a calibrated nozzle nozzle, fuel particles can be significantly smaller in size compared to atomization of gasoline during atomization (Fig. 3, b). Gasoline is sprayed especially effectively in a narrow beam under high pressure (Fig. 3, c).

It has been established that when gasoline is sprayed onto particles with a diameter of less than 15...20 microns, its mixing with atmospheric oxygen does not occur as a suspension of particles, but at the molecular level. This makes the TV mixture more resistant to changes in temperature and pressure in the cylinder and long pipes of the intake manifold, which contributes to its more complete combustion.

This is how the idea was born to replace the spray jets of a mechanical inertia carburetor with a central inertia-free injection nozzle (CFI), which opens for a given time according to an electric pulse control signal from the electronic automation unit. At the same time, in addition to high-quality atomization and effective mixing of gasoline with air, it is easy to obtain higher accuracy of their dosing in the TV mixture at all possible modes engine operation.

Thus, due to the use of a fuel supply system with gasoline injection, the engines of modern passenger cars do not have the above-mentioned disadvantages inherent in carburetor engines, i.e. they are more economical, have a higher specific power, maintain constant torque over a wide range of rotation speeds, and the emission of harmful substances into the atmosphere with exhaust gases is minimal.

3. Gasoline injection system "Mono-Jetronic"

The first system of central single-point pulse fuel injection for gasoline engines of passenger cars was developed by BOSCH in 1975. This system was called "Mono-Jetronic" (Monojet - single jet) and was installed on a Volkswagen car.

In Fig. Figure 4 shows the central injection unit of the Mono-Jetronic system. The figure shows that the central injection nozzle (CI) is installed on a standard intake manifold instead of a conventional carburetor.

But unlike a carburetor, in which automatic mixture formation is implemented by mechanical control, a mono injection system uses purely electronic control.

In Fig. 5 shows a simplified functional diagram Mono-Jetronic systems.

The electronic control unit (ECU) operates from input sensors 1-7, which record the current state and operating mode of the engine. Based on the combination of signals from these sensors and using information from the three-dimensional injection characteristic, the start and duration of injection are calculated in the computer. open state central nozzle 15.

Based on the calculated data, an electric pulse control signal S for the digital filter is generated in the ECU. This signal acts on winding 8 of the injector magnetic solenoid, stop valve 11 of which opens, and through the spray nozzle 12, gasoline is forcibly sprayed at a pressure of 1.1 bar in the fuel supply line 19 into the intake manifold through the open throttle valve 14.

For given aperture sizes throttle valve and the calibrated cross-section of the spray nozzle, the mass amount of air passed into the cylinders is determined by the degree of opening of the throttle valve, and the mass amount of gasoline injected into the air flow is determined by the duration of the open state of the nozzle and the retaining (working) pressure in the fuel supply line 19.

In order for gasoline to burn completely and most efficiently, the masses of gasoline and air in the TV mixture must be in a strictly defined ratio, equal to 1/14.7 (for high-octane grades of gasoline). This ratio is called stoichiometric, and it corresponds to the coefficient a of excess air, equal to one. Coefficient a = Md/M0, where M0 is the amount of air mass theoretically required for complete combustion of a given portion of gasoline, and Md is the mass of actually burned air.

Hence it is clear that any fuel injection system must have a meter for the mass of air admitted into the engine cylinders during suction.

In the "Mono-Jetronic" system, the air mass is calculated in the ECU based on the readings of two sensors (see Fig. 4): intake air temperature (IAT) and throttle valve position (ATP). The first is located directly in the air flow path at the top of the central injection nozzle and is a miniature semiconductor thermistor, and the second is a resistive potentiometer, the motor of which is mounted on the rotary axis (PS) of the throttle valve.

Since a specific angular position of the throttle valve corresponds to a strictly defined volumetric amount of air passed through, the throttle potentiometer functions as an air flow meter. In the Mono-Jetronic system it is also an engine load sensor.

But the mass of intake air largely depends on temperature. Cold air is denser and therefore heavier. As the temperature increases, air density and mass decrease. The influence of temperature is taken into account by the DTV sensor.

The DTV intake air temperature sensor, like a semiconductor thermistor with a negative temperature coefficient of resistance, changes the resistivity value from 10 to 2.5 kOhm when the temperature changes from -30 to +20°C. The DTV sensor signal is used only in this temperature range. In this case, the basic duration of gasoline injection is adjusted by the ECU in the range of 20...0%. If the intake air temperature is above +20°C, then the signal from the DTV sensor is blocked in the ECU and the sensor is not used.

Signals from the throttle position (TAP) and intake air temperature (IAT) sensors in cases of their failures are duplicated in the ECU by signals from the engine speed sensors (RPS) and engine coolant temperature (ITC).

Based on the air volume calculated in the ECU, as well as the signal about the engine speed, which comes from the ignition system speed sensor, the required (basic) duration of the open state of the central injection nozzle is determined.

Since the supporting pressure Рт in the fuel supply line (FBM) is constant (for "Mono-Jetronic" Рт = 1...1.1 bar), and throughput the injector is given by the total cross-section of the spray nozzle holes, then the open time of the injector uniquely determines the amount of injected gasoline. The injection moment (in Fig. 5, the signal from the UHF sensor) is usually set simultaneously with the signal to ignite the TV mixture from the ignition system (through 180° of rotation of the internal combustion engine crankshaft).

Thus, with electronic control of the mixture formation process, ensuring high accuracy of dosage of injected gasoline into a measured amount of air mass is an easily solved problem and, ultimately, dosing accuracy is determined not by electronic automation, but by the manufacturing accuracy and functional reliability of the input sensors and injection nozzle.

In Fig. Figure 6 shows the main part of the Mono-Jetronic system - the central injection nozzle (CI).

The central injection nozzle is a gas valve that is opened by an electrical impulse coming from the electronic control unit. For this purpose, the nozzle contains an electromagnetic solenoid 8 with a movable magnetic core 14. The main problem when creating valves for pulse injection is the need to ensure high speed of operation of the valve shut-off device 9 for both opening and closing. The solution to the problem is achieved by lightening the magnetic core of the solenoid, increasing the current in the pulse control signal, selecting the elasticity of the return spring 13, as well as the shape of the ground surfaces for the spray nozzle 10.

The nozzle nozzle (Fig. 6, a) is made in the form of a bell of capillary tubules, the number of which is usually at least six. The angle at the top of the bell determines the opening of the injection jet, which has the shape of a funnel. With this shape, a stream of gasoline does not hit the throttle valve even when it is opened slightly, but flies through two thin crescents of the opened gap.

The central nozzle of the Mono-Jetronic system reliably ensures the minimum duration of the open state of the spray nozzle 11 for 1 ± 0.1 ms. During this time and at an operating pressure of 1 bar, about one milligram of gasoline is injected through a spray nozzle with an area of ​​0.08 mm2. This corresponds to a fuel consumption of 4 l/h at minimum idle speed(600 rpm) warm engine. When starting and warming up a cold engine, the injector opens for a longer time (up to 5...7 ms). But on the other hand, the maximum injection duration on a warm engine (injector open time) is limited by the maximum engine crankshaft speed (6500...7000 min-1) in full throttle mode and cannot be more than 4 ms. In this case, the clock frequency of the injector shut-off device at idle is at least 20 Hz, and at full load - no more than 200...230 Hz.

The DPD throttle position sensor (throttle potentiometer), shown in Fig. 1, is manufactured with special care. 7. Its sensitivity to engine rotation must meet the requirement of ±0.5 angular degrees of rotation of the throttle axis 13. The strict angular position of the throttle axis determines the beginning of two engine operating modes: idle mode (3±0.5°) and full load mode (72.5±0.5°).

To ensure high accuracy and reliability, the resistive potentiometer tracks, of which there are four, are connected according to the circuit shown in Fig. 7, b, and the axis of the potentiometer engine (two-contact engine) is seated in a backlash-free Teflon plain bearing.

The potentiometer and the ECU are connected to each other by a four-wire cable through a contact connector. To increase the reliability of connections, the contacts in the connector and in the potentiometer chip are gold-plated. Contacts 1 and 5 are intended for supplying a reference voltage of 5±0.01 V. Contacts 1 and 2 are for removing signal voltage when turning the throttle valve at an angle from 0 to 24° (0...30 - idle mode; 3.. .24° - low engine load mode). Contacts 1 and 4 - to relieve signal voltage when turning the throttle valve at an angle from 18 to 90° (18...72.5° - medium load mode, 72.5...90° - full engine load mode).

The signal voltage from the throttle potentiometer is additionally used:
to enrich the TV mixture when accelerating the car (the speed of change of the signal from the potentiometer is recorded);
to enrich the TV mixture in full load mode (the signal value from the potentiometer is recorded after turning the throttle valve 72.5° upward);
to stop fuel injection in forced idle mode (a potentiometer signal is registered if the throttle valve open angle is less than 3°. At the same time, the engine speed W is monitored: if W>2100 min-1, then the fuel supply is stopped and restored again at W
Interesting feature The "Mono-Jetronic" injection system is the presence in its composition of a subsystem for stabilizing idle speed using an electric servo drive, which acts on the throttle axis (Fig. 8). The electric servo drive is equipped with a reversible DC electric motor 11.

The servo drive is switched on in idle mode and, together with the circuit for disabling the vacuum ignition timing regulator (idling stabilization - Fig. 2), ensures stabilization of the engine speed in this mode.

This idle stabilization subsystem works as follows.

When the throttle valve open angle is less than 3°, signal K (see Fig. 9)

It is a signal for the ECU in idle mode (the VC limit switch is closed by the servo drive rod). Based on this signal, the shut-off pneumatic valve ZPK is activated and the vacuum channel from the after-throttle zone of the intake manifold to the vacuum regulator VR is closed. Vacuum regulator from this moment it does not work and the ignition timing becomes equal to the value of the installation angle (6° before TDC). At the same time, the engine runs stably at idle speed. If at this time the air conditioner or other powerful consumer of engine energy is turned on (for example, headlights high beam indirectly through the generator), then its speed begins to fall. The engine may stall. To prevent this from happening, on command from electronic circuit Idle speed control (ESCH) in the controller turns on the electric servo drive, which slightly opens the throttle valve. The speed increases to the nominal value for the given engine temperature. It is clear that when the load is removed from the engine, its speed is reduced to normal by the same electric servo drive.

The ECU of the "Mono-Jetronic" system has a MCP microprocessor (see Fig. 5) with permanent and random access memory (storage unit). The reference three-dimensional injection characteristic (TCI) is “hardwired” into the permanent memory. This characteristic is to some extent similar to the three-dimensional ignition characteristic, but differs in that its output parameter is not the ignition timing, but the time (duration) of the open state of the central injection nozzle. The input coordinates of the TCV characteristic are the engine speed (the signal comes from the ignition system controller) and the volume of intake air (calculated by the microprocessor in the injection ECU). The reference characteristic of the TC contains reference (basic) information about the stoichiometric ratio of gasoline and air in the TC mixture under all possible modes and operating conditions of the engine. This information is selected from the memory of the memory into the microprocessor of the ECU according to the input coordinates of the TC characteristics (according to signals from the sensors DOD, DPD, DTV) and is corrected according to signals from the coolant temperature sensor (LTD) and oxygen sensor(KD).

Separate mention must be made about the oxygen sensor. Its presence in the injection system allows the composition of the TV mixture to be kept constantly in a stoichiometric ratio (a = 1). This is achieved by the fact that the pressure sensor operates in a deep adaptive feedback circuit from the exhaust gas system to the fuel supply system (to the injection system).

It reacts to the difference in oxygen concentration in the atmosphere and in the exhaust gases. In fact, the CD sensor is a chemical current source of the first kind (galvanic cell) with a solid electrolyte (special cellular metal ceramics) and high (not lower than 300°C) operating temperature. The EMF of such a sensor depends almost according to a stepwise law on the difference in oxygen concentration on its electrodes (platinum-radium film coating on different sides of the porous ceramic). The greatest steepness (difference) of the EMF step occurs at the value a=1.

The pressure sensor is screwed into the pipe exhaust channel(for example, into the exhaust manifold) and its sensitive surface (positive electrode) appears in the flow exhaust gases. There are slots above the sensor mounting thread through which the outer negative electrode communicates with atmospheric air. On cars with a catalytic gas neutralizer, the oxygen sensor is installed in front of the converter and has an electrical heating coil, since the temperature of the exhaust gases in front of the converter can be below 300°C. In addition, electrical heating of the oxygen sensor speeds up its preparation for operation.

The sensor is connected to the injection computer by signal wires. When a lean mixture (a>1) enters the cylinders, the oxygen concentration in the exhaust gases is slightly higher than the standard one (at a=1). The pressure sensor produces a low voltage (about 0.1 V) and the ECU, based on this signal, adjusts the duration of gasoline injection to increase it. Coefficient a is again approaching unity. When the engine is running rich mixture the oxygen sensor produces a voltage of about 0.9 V and works in reverse.

It is interesting to note that the oxygen sensor is involved in the process of mixture formation only in engine operating modes in which the enrichment of the TV mixture is limited to a>0.9. These are such modes as load at low and medium speeds and idling on a warm engine. Otherwise, the pressure sensor is turned off (blocked) in the ECU and the composition of the TV mixture is not adjusted based on the oxygen concentration in the exhaust gases. This occurs, for example, in the modes of starting and warming up a cold engine and in its forced modes (acceleration and full load). In these modes, a significant enrichment of the TV mixture is required and therefore the activation of the oxygen sensor ("pressing" coefficient a to unity) is unacceptable here.

In Fig. Figure 10 shows a functional diagram of the Mono-Jetronic injection system with all its components.

Any injection system in its fuel supply subsystem necessarily contains a closed fuel ring, which starts from the gas tank and ends there. This includes: a fuel tank BB, an electric fuel pump EBN, a fine fuel filter FTOT, a fuel distributor PT (in the Mono-Jetronic system this is the central injection nozzle) and a pressure regulator RD, which operates on the principle of a bleed valve when the specified operating pressure in a closed ring is exceeded (for the Mono-Jetronic system 1...1.1 bar).

The closed fuel ring performs three functions:

Using a pressure regulator, maintains the required constant operating pressure for the fuel distributor;

Using a spring-loaded diaphragm in the pressure regulator, it retains some residual pressure (0.5 bar) after turning off the engine, which prevents the formation of steam and air locks in the fuel lines when the engine cools down;

Provides cooling of the injection system due to constant circulation of gasoline in a closed circuit. In conclusion, it should be noted that the "Mono-Jetronic" system is used only on passenger cars of the average consumer class, for example, such West German cars as "Volkswagen-Passat", "Volkswagen-Polo", "Audi-80".
REPAIR&SERVICE-2"2000

Sometimes called center injection, it became widely used in passenger cars in the 1980s. This power system got its name due to the fact that fuel was supplied to the intake manifold at only one point.

Many systems of that time were purely mechanical, electronic control they didn't have. Often, the basis for such a power system was a conventional carburetor, from which all “extra” elements were simply removed and one or two nozzles were installed in the area of ​​its diffuser (therefore, central injection was relatively inexpensive). For example, this is how the TBI (“Throttle Body Injection”) system from the company “ General Motors”.

But, despite its apparent simplicity, central injection has a very important advantage Compared to a carburetor, it more accurately doses the combustible mixture in all engine operating modes. This allows you to avoid failures in the operation of the motor, and also increases its power and efficiency.

Over time, the advent of electronic control units made central injection more compact and reliable. It has become easier to adapt it to work on different engines.

However, single-point injection also inherited a number of disadvantages from carburetors. For example, high resistance to air entering the intake manifold and poor distribution fuel mixture for individual cylinders. As a result, an engine with such a power system does not have very high performance. Therefore, today central injection is practically not found.

By the way, the General Motors concern also developed an interesting type of central injection - CPI (“Central Port Injection”). In such a system, one nozzle sprayed fuel into special tubes that were led into the intake manifold of each cylinder. This was a kind of prototype of distributed injection. However, due to low reliability, the use of CPI was quickly abandoned.

Distributed

OR MULTI-POINT fuel injection is the most common engine power supply system on modern cars today. It differs from the previous type primarily in that there is an individual nozzle in the intake manifold of each cylinder. At certain points in time, it injects the required portion of gasoline directly into the intake valves of “its” cylinder.

Multipoint injection can be parallel or sequential. In the first case, at a certain point in time, all the injectors fire, the fuel is mixed with air, and the resulting mixture waits for the intake valves to open to enter the cylinder. In the second case, the operating period of each injector is calculated individually so that gasoline is supplied for a strictly defined time before the valve opens. The efficiency of such injection is higher, so sequential systems have become more widespread, despite the more complex and expensive electronic “stuffing”. Although sometimes there are cheaper combined schemes (in this case, the injectors fire in pairs).

At first, distributed injection systems were also mechanically controlled. But over time, electronics prevailed here too. After all, by receiving and processing signals from many sensors, the control unit not only commands the actuators, but can also signal the driver about a malfunction. Moreover, even in the event of a breakdown, the electronics switches to emergency mode work, allowing the car to independently reach the service station.

Distributed injection has a number of advantages. In addition to preparing the combustible mixture of the correct composition for each engine operating mode, such a system also more accurately distributes it among the cylinders and creates minimal resistance to the air passing through the intake manifold. This allows you to improve many engine indicators: power, efficiency, environmental friendliness, etc. Among the disadvantages of multipoint injection, perhaps only the rather high cost can be mentioned.

Direct..

“Goliath GP700” became the first production car, the engine of which received fuel injection.

INJECTION (also sometimes called direct) differs from previous types of power systems in that in this case the injectors deliver fuel directly to the cylinders (bypassing the intake manifold), just like a diesel engine.

In principle, this power system design is not new. Back in the first half of the last century it was used on aircraft engines(for example, on the Soviet La-7 fighter). On passenger cars direct injection appeared a little later - in the 50s of the twentieth century, first on the Goliath GP700 car, and then on the famous Mercedes-Benz 300SL. However, after some time, automakers practically abandoned the use of direct injection; it remained only racing cars.

The fact is that the cylinder head of a direct injection engine turned out to be very complex and expensive to manufacture. In addition, for a long time the designers were unable to achieve stable operation of the system. Indeed, for effective mixture formation during direct injection, it is necessary that the fuel is well atomized. That is, it was supplied to the cylinders under high pressure. And this required special pumps capable of providing it. As a result, at first, engines with such a power system turned out to be expensive and uneconomical.

However, with the development of technology, all these problems were solved, and many automakers returned to the long-forgotten scheme. The first was Mitsubishi, which in 1996 installed an engine with direct fuel injection (brand designation - GDI) on the Galant model, then other companies began to use similar solutions. In particular, “Volkswagen” and “Audi” (FSI system), “Peugeot-Citroen” (HPA), “Alfa Romeo” (JTS) and others.

Why did such a power system suddenly interest leading automakers? It's all very simple - engines with direct injection are able to operate on a very lean working mixture (with a small amount of fuel and a large amount of air), so they are characterized by good efficiency. In addition, supplying gasoline directly to the cylinders allows you to increase the compression ratio of the engine, and therefore its power.

The direct injection power system can operate in different modes. For example, when uniform motion car at a speed of 90-120 km/h, the electronics supply very little fuel to the cylinders. Basically so super poor working mixture very difficult to set on fire. Therefore, direct injection engines use pistons with a special recess. It directs the bulk of the fuel closer to the spark plug, where conditions for ignition of the mixture are better.

When driving with high speed or during sharp accelerations, significantly more fuel is supplied to the cylinders. Accordingly, due to the strong heating of engine parts, the risk of detonation increases. To avoid this, the injector injects fuel into the cylinder with a wide spray, which fills the entire volume of the combustion chamber and cools it.

If the driver requires sharp acceleration, the injector fires twice. First, at the beginning of the intake stroke, a small amount of fuel is sprayed to cool the cylinder, and then at the end of the compression stroke, the main charge of gasoline is injected.

But, despite all their advantages, engines with direct injection are not yet widespread enough. Reason - high price and demands on fuel quality. In addition, a motor with such a power system runs louder than usual and vibrates more strongly, so designers have to further strengthen some engine parts and improve sound insulation engine compartment.

Author Edition Klaxon No. 4 2008 Photo photo from the Klaxon archive

The fuel injection system is used to dose fuel into an internal combustion engine at a strictly defined point in time. The characteristics of this system determine the power, efficiency and environmental class car engine. Injection systems may have different design and design options, which characterizes their effectiveness and scope of application.

Brief history of appearance

The fuel injection system began to be actively introduced in the 70s, as a response to the increased level of emissions of pollutants into the atmosphere. It was borrowed from the aircraft industry and was an environmentally safer alternative carburetor engine. The latter was equipped mechanical system fuel supply, in which fuel entered the combustion chamber due to the pressure difference.

The first injection system was almost entirely mechanical and was characterized by low efficiency. The reason for this was insufficient level technical progress, which could not fully realize her potential. The situation changed in the late 90s with the development of electronic engine control systems. The electronic control unit began to control the amount of fuel injected into the cylinders and percentage components of the air-fuel mixture.

Types of injection systems for gasoline engines

There are several main types of fuel injection systems, which differ in the way the air-fuel mixture is formed.

Single injection or central injection

Scheme of operation of the mono-injection system

The central injection scheme provides for one injector, which is located in the intake manifold. Such injection systems can only be found on older passenger cars. It consists of the following elements:

• Pressure regulator - provides a constant operating pressure of 0.1 MPa and prevents the appearance of air locks in the fuel system.
• Injection nozzle - pulses gasoline into the engine intake manifold.
• Throttle valve - regulates the volume of supplied air. May have mechanical or electric drive.
• Control unit - consists of a microprocessor and a memory unit, which contains reference data for fuel injection characteristics.
• Position sensors crankshaft engine, throttle position, temperature, etc.

Gasoline injection systems with one injector operate according to the following scheme:

• The engine is running.
• Sensors read and transmit information about the state of the system to the control unit.
• The obtained data is compared with the reference characteristic, and, based on this information, the control unit calculates the moment and duration of opening the nozzle.
• A signal is sent to the electromagnetic coil to open the injector, which leads to the supply of fuel to the intake manifold, where it is mixed with air.
• A mixture of fuel and air is supplied to the cylinders.

Multiport injection (MPI)

A distributed injection system consists of similar elements, but in this design there are separate injectors for each cylinder, which can open simultaneously, in pairs or one at a time. Mixing of air and gasoline also occurs in the intake manifold, but, unlike single injection, fuel is supplied only in intake tracts corresponding cylinders.

Diagram of operation of a system with distributed injection

The control is carried out electronically (KE-Jetronic, L-Jetronic). These are universal Bosch fuel injection systems that are widely used.

Operating principle of distributed injection:

• Air is supplied to the engine.
• Using a number of sensors, the volume of air, its temperature, the speed of rotation of the crankshaft, as well as the throttle position parameters are determined.
• Based on the data received the electronic unit control determines the volume of fuel that is optimal for the amount of air supplied.
• A signal is given and the corresponding injectors open for the required period of time.

Direct fuel injection (GDI)

The system provides for the supply of gasoline through separate injectors directly into the combustion chambers of each cylinder under high pressure, where air is simultaneously supplied. This injection system provides the most accurate concentration of the air-fuel mixture, regardless of engine operating mode. In this case, the mixture burns almost completely, thereby reducing the volume of harmful emissions into the atmosphere.

Direct injection system operation diagram

This injection system is complex in design and sensitive to fuel quality, making it expensive to manufacture and operate. Since injectors operate under more aggressive conditions, for correct operation Such a system requires high fuel pressure, which must be at least 5 MPa.

Structurally, the direct injection system includes:

• High pressure fuel pump.
• Fuel pressure control.
• Fuel rail.
• Safety valve(installed on the fuel rail to protect system elements from pressure increases above the permissible level).
• High pressure sensor.
• Injectors.

An electronic injection system of this type from Bosch is called MED-Motronic. The principle of its operation depends on the type of mixture formation:

• Layer-by-layer - implemented at low and medium engine speeds. Air is supplied to the combustion chamber at high speed. Fuel is injected towards the spark plug and, mixing with air along the way, ignites.
• Stoichiometric. When you press the gas pedal, the throttle valve opens and fuel is injected simultaneously with the air supply, after which the mixture ignites and burns completely.
• Homogeneous. Intensive air movement is provoked in the cylinders, while gasoline is injected during the intake stroke.

Direct fuel injection in a gasoline engine is the most promising direction in the evolution of injection systems. It was first implemented in 1996 on passenger cars Mitsubishi cars Galant, and today most major automakers install it on their cars.

A fuel supply system is needed to receive fuel from the gas tank, filter it further, and also form an oxygen-fuel mixture and transfer it to the engine cylinders. Currently, there are several types of fuel systems. The most common in the 20th century was the carburetor, but today the injection system is becoming increasingly popular. There was also a third one - mono-injection, which was good only because it made it possible to slightly reduce fuel consumption. Let's take a closer look at the injection system and understand its operating principle.

General provisions

Majority modern engine fuels are similar. The difference can only lie at the stage of mixture formation. Part fuel system includes the following nodes:

1. The fuel tank is a compact product that has a pump and a filter to remove mechanical particles. The main purpose is fuel storage.
2. Fuel lines form a complex of hoses and tubes for moving fuel from the tank to the mixture formation system.
3. Mixture formation device. In our case we will talk about the injector. This unit is designed to produce an emulsion (air-fuel mixture) and supply it to the cylinders during engine operation.
4. Control unit for the mixture formation system. Installed only on injection engines, due to the need to monitor sensors, injectors and valves.
5. Fuel pump. In most cases, the submersible option is used. It is a low-power electric motor that is connected to a liquid pump. Lubrication is provided by fuel, and long-term use of a vehicle with an amount of fuel of less than 5 liters can lead to failure of the electric motor.

In short, an injector is a point supply of fuel through a nozzle. Electronic signal comes from the control unit. Although the injector has a number of significant advantages in front of the carburetor, it has not been used for a long time. This was due to the technical complexity of the product, as well as the low maintainability of failed parts. Currently, point injection systems have practically replaced the carburetor. Let's take a closer look at why the injector is so good and what its features are.

Features of fuel equipment

The car has always been the object of attention of environmentalists. Exhaust gases are released directly into the atmosphere, which can cause pollution. Diagnostics of the fuel system showed that the amount of emissions due to incorrect mixture formation increases significantly. For this simple reason, it was decided to install a catalytic converter. However, this device showed good results only with a high-quality emulsion, and in case of any deviations its effectiveness dropped significantly. It was decided to replace the carburetor with a more accurate injection system, which was an injector. The first options included a large number of mechanical components and, according to research, such a system became worse and worse as the vehicle was used. This was quite natural, since important nodes and the working parts became dirty and failed.

In order for the injection system to be able to correct itself, an electronic control unit (ECU) was created. Along with the built-in lambda probe, which is located in front of the catalytic converter, this gave good performance. It’s safe to say that fuel prices today are quite high, and the injector is good because it allows you to save gasoline or diesel. In addition to this, there are the following advantages:

1. Increase performance characteristics motor. In particular, increased power by 5-10%.
2. Improving the dynamic performance of the vehicle. The injector is more sensitive to changes in loads and itself adjusts the composition of the emulsion.
3. The optimal fuel-air mixture reduces the amount and toxicity of exhaust gases.
4. The injection system starts easily regardless of weather conditions, which is a significant advantage over carburetor engines.

Fuel injection system and its design

First of all, it is worth noting the fact that modern injection engines are equipped with injectors, the number of which is equal to the number of cylinders. The injectors are connected to each other by a ramp. There, the fuel is kept under slight pressure, and it is created by an electrical device - a gas pump. The amount of fuel injected directly depends on the duration of opening of the nozzle, which is determined by the control unit. To do this, indicators are taken from various sensors that are installed throughout the vehicle. Now we will look at the main ones:

1. Serves to determine whether the cylinders are filled with air. In the event of a breakdown, the readings are ignored, and tabular data is taken as the main indicators.
2. The position sensor reflects the load on the engine, which is determined by the position of the throttle, cyclic air filling and engine speed.
3. Refrigerant temperature sensor. Using this controller, the electric fan is controlled and the fuel supply and ignition are adjusted. In the event of a malfunction, immediate diagnosis of the fuel system is not necessary. The temperature is taken depending on the duration of operation of the internal combustion engine.
4. The crankshaft (crankshaft) position sensor is needed to synchronize the system as a whole. The controller calculates not only the engine speed, but also its position at a certain point in time. Since it is a polar sensor, if it malfunctions, further operation of the vehicle is not possible.
5. An oxygen sensor is needed to determine the % of oxygen in gases emitted into the atmosphere. Information from this controller is transmitted to the computer, which, depending on the readings, adjusts the emulsion.

It is worth paying attention to the fact that not all vehicles with an injector are equipped with an oxygen sensor. Only those cars that are equipped with a catalytic converter with Euro-2 and Euro-3 toxicity standards have them.

Types of injection systems: single point injection

All systems are currently in active use. They are classified depending on the number of injectors and the location of the fuel supply. There are three injection systems in total:

• single-point (mono-injection);
• multipoint (distribution);
• direct.

First, let's look at single point injection systems. They were created immediately after carburetor ones and were considered more advanced, but nowadays they are gradually losing their popularity due to many reasons. There are several undeniable advantages of such systems. The main ones are significant fuel savings. Considering that fuel prices are quite high today, such an injector is relevant. Interestingly, this system contains slightly less electronics, therefore it is more reliable and stable. When information from the sensors is transmitted to the control element, the injection parameters immediately change. A very interesting thing is that almost any one can be converted to single-point injection without significant structural changes. The main disadvantage of such systems is the low throttle response of the internal combustion engine, as well as the deposition of a significant amount of fuel on the walls of the manifold, although this problem was also inherent in carburetor models.

Since in this case there is only one nozzle, it is located on the intake manifold in place of the carburetor. Since the nozzle was in good location and was constantly under a flow of cold air, then its reliability was at top level, and the design was extremely simple. Flushing a fuel system with single-point injection did not take much time, since it was enough to blow out only one injector, but increased environmental requirements led to the development of other, more modern systems.

Multipoint injection systems

Distributed injection is considered more modern, complex and less reliable. In this case, each cylinder is equipped with an isolated injector, which is located in the intake manifold in close proximity to the intake valve. Consequently, the emulsion is supplied separately. As noted above, with such an injection, the power of the internal combustion engine can be increased to 5-10%, which will be noticeable when driving on the road. Another interesting point: this fuel injection system is good because the nozzle is located very close to the intake valve. This minimizes fuel settling on the walls of the manifold, which makes it possible to achieve significant fuel savings.

There are several types of multipoint injection:

1. Simultaneous - all injectors open at the same time.
2. Pair-parallel - opening of nozzles in pairs. One injector opens during the intake stroke, and the second before the exhaust stroke. Currently, such a system is used only at the moment emergency start ICE in case of crankshaft position failure).
3. Phased - each injector is controlled separately and opens before the intake stroke.

In this case, the system is quite complex and relies entirely on the precision of the electronics. For example, flushing the fuel system will require much more time, since each injector must be flushed. Now let's go further and look at another popular type of injection.

Direct injection

Injection cars with such systems can be considered the most environmentally friendly. The main purpose of introducing this injection method is to improve the quality of the fuel mixture and slightly increase the efficiency of the vehicle engine. The main advantages of this solution are as follows:

• thoroughly spraying the emulsion;
• formation of a high-quality mixture;
• effective use of emulsion at various stages of internal combustion engine operation.

Based on these advantages, we can say that such systems save fuel. This is especially noticeable during quiet driving in urban conditions. If we compare two cars with the same engine size, but different injection systems, for example, direct and multipoint, then the direct system will have noticeably better dynamic characteristics. The exhaust gases are less toxic, and the liter power taken will be slightly higher due to air cooling and the fact that the pressure in the fuel system is slightly increased.

But you should pay attention to sensitivity direct systems injection to fuel quality. If we take into account the standards of Russia and Ukraine, the sulfur content should not exceed 500 mg per 1 liter of fuel. At the same time, European standards imply a content of this element of 150, 50 and even 10 mg per liter of gasoline or diesel.

If we briefly consider this system, it looks like this: the injectors are located in. Based on this, injection is carried out directly into the cylinders. It is worth noting that this injection system is suitable for many gasoline engines. As noted above, high pressure is used in the fuel system, under which the emulsion is supplied directly into the combustion chamber, bypassing the intake manifold.

Fuel injection system: driving on a lean mixture

We looked a little higher direct injection, which was first used on Mitsubishi cars, which had the abbreviation GDI. Let's take a brief look at one of the main modes - running on a lean mixture. Its essence lies in the fact that the vehicle in this case operates under light loads and moderate speeds of up to 120 kilometers per hour. Fuel injection is carried out by a torch in final stage compression. Reflecting from the piston, the fuel mixes with air and enters the spark plug area. It turns out that the mixture in the chamber is significantly leaner, however, its charge in the area of ​​the spark plug can be considered optimal. This is enough to ignite it, after which the rest of the emulsion lights up. In fact, such a fuel injection system ensures normal operation of the internal combustion engine even at an air/fuel ratio of 40:1.

This is a very effective approach that allows you to significantly save fuel. But it is worth noting that the issue of neutralizing exhaust gases has become acute. The fact is that the catalyst is ineffective because nitrogen oxide is formed. In this case, exhaust gas recirculation is used. Special system ERG allows you to dilute the emulsion with exhaust gases. This slightly reduces the combustion temperature and neutralizes the formation of oxides. However, this approach will not increase the load on the engine. To partially solve the problem, a storage catalyst is used. The latter is extremely sensitive to fuel with a high sulfur content. For this reason, periodic inspection of the fuel system is required.

Homogeneous mixture formation and 2-stage mode

Power mode (uniform mixture formation) - perfect solution for aggressive driving in city conditions, overtaking, as well as driving on highways and highways. In this case, a conical torch is used; it is less economical compared to the previous option. Injection occurs during the intake stroke, and the resulting emulsion usually has a ratio of 14.7:1, that is, close to stoichiometric. In essence, this automatic fuel supply system is exactly the same as the distribution system.

The two-stage mode involves fuel injection on the compression stroke and also on the start stroke. The main task is to sharply increase the engine. A striking example efficient work such a system is movement at low speeds and sharp pressing to the accelerator. In this case, the likelihood of detonation increases significantly. For this simple reason, instead of one stage, injection takes place in two.

At the first stage, a small amount of fuel is injected during the intake stroke. This allows you to slightly lower the air temperature in the cylinder. We can say that the cylinder will contain an ultra-lean mixture in a ratio of 60:1, therefore, detonation is impossible as such. At the final stage of the compression stroke, a jet of fuel is injected, which brings the emulsion to a rich emulsion in a ratio of approximately 12:1. Today we can say that such an engine fuel system was introduced only for Vehicle European market. This is due to the fact that Japan is not characterized by high speeds, therefore, there are no high loads on the engine. In Europe, there are a large number of highways and autobahns, so drivers are used to driving fast, and this puts a lot of stress on the internal combustion engine.

Something else interesting

It is worth paying attention to the fact that, unlike carburetor systems, injection systems require regular checking of the fuel system. This is because a large number of complex electronics can fail. As a result, this will lead to undesirable consequences. For example, excess air in the fuel system will lead to a violation of the emulsion composition and an incorrect mixture ratio. In the future, this affects the engine, appears unstable work, controllers fail, etc. Essentially, an injector is a complex system that determines when a spark needs to be applied to the cylinders, how to deliver a high-quality mixture to the cylinder block or intake manifold, when to open the injectors and what ratio of air and gasoline should be in emulsion. All these factors affect the synchronized operation of the fuel system. The interesting thing is that without most of the controllers, the machine can work properly, and there will be no significant deviations, since there are emergency records and tables that will be used.

The efficiency of the internal combustion engine in our case is determined by how correct the data received from the controllers will be. The more precise they are, the less possible various malfunctions fuel system. Important role The speed of operation of the system as a whole also plays a role. Unlike carburetors, it is not required manual adjustment, and this eliminates errors during calibration work. Therefore, we will get more complete combustion mixtures and an environmentally friendly system.

Conclusion

In conclusion, it is worth talking a little about the disadvantages that are inherent in injection systems. The main disadvantage is the high cost of the internal combustion engine. By and large, the cost of such units will be approximately 15% higher, which is significant. But there are other disadvantages. For example, a faulty fuel system valve in most cases cannot be repaired, which is due to a leak, so it simply needs to be replaced. This also applies to the maintainability of equipment in general. Some components and parts are much easier to buy new than to spend money on repairing them. This quality is not inherent in carburetor vehicles, where you can go through all the important components and restore their functionality without a lot of time and effort. Without any doubts, electronic system fuel supply is repaired with great effort and resources. Complex electronics It can hardly be restored at the first service station that comes along.

Well, we talked to you about what it is injection systems. As you can see, this is a very interesting topic to talk about. We can talk a lot more about the benefits of injectors and the ability to instantly adjust engine operation. But we have already talked about the main points. Remember to check regularly for possible defects. For example, due to Low quality fuel, which is actually typical in our country, the injectors often become clogged. Because of this, the engine begins to operate intermittently, power drops, and the mixture becomes too lean or vice versa. All this has a very bad effect on the car as a whole, so constant and regular monitoring is needed. In addition, try to refuel only with the gasoline recommended by the manufacturer of your vehicle.