How an injector works. Central fuel injection

11.04.2019

This system fuel supply, installed on modern gasoline engines. This fuel supply system is gradually replacing the power supply system. Engines with such a system are called injection engines.

In the late 60s and early 70s of the twentieth century, the problem of pollution became acute. environment industrial waste, among which a significant part was cars. Until that time, no one was interested in the composition of combustion products. 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 channels with high speed, suction 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. 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 it was proposed to install in the exhaust system catalytic converter exhaust gases. 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. To maintain this ratio working mixture carburetor systems no longer fit. 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, given the wear and contamination of the elements of the system and the engine itself. internal combustion during his service. 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. Introduced into the injection system feedback- V exhaust system, directly in front of the catalyst, put an oxygen content sensor in exhaust gases, the so-called lambda probe. This system was developed already taking into account the presence of such a fundamental element for all subsequent systems as the electronic unit control (ECU). Based on the signals from the oxygen sensor, the ECU adjusts the fuel supply to the engine, accurately maintaining desired composition mixtures.

To date, the injection (or, scientifically speaking, injection) engine has almost completely replaced the outdated ones. The injection engine significantly improves the performance and power performance of the car (acceleration dynamics, environmental performance, fuel consumption).

Injection systems fuel supply have the following main advantages over carburetor:

Accurate dosing of fuel and, consequently, its more economical consumption;
Decrease. It is achieved due to the optimal fuel-air mixture and the use of parameter sensors exhaust gases;
An increase in engine power by about 7-10%. Occurs by improving the filling of cylinders, optimal installation ignition timing corresponding to the operating mode of the engine;
Improvement dynamic properties car. The injection system immediately responds to any load changes by adjusting the parameters of the fuel-air mixture;
Easy start 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 nozzles are connected to 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.

Sensor mass flow air 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 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.

About the results of a survey of sensors defined in the program, the ECU program controls executive mechanisms, which include: nozzles, 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 specific model)

Of all of 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. On idle engine 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.

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 they 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 possibility of automatic tuning at different speeds and, accordingly, an improvement in the filling of the cylinders, as a result, at the same maximum power the car accelerates much faster;
Gasoline injected close up inlet valve, which significantly reduces losses due to settling in the intake manifold and allows for more precise adjustment of the fuel supply.

direct injection as next and effective remedy in optimizing the combustion of the mixture and increasing efficiency gasoline engine 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" (popularly - injector) motors (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 low in sulfur and mechanical impurities to ensure normal work fuel equipment.

And just the main discrepancy between GOSTs currently in force in Russia 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 calibrated nozzle holes and plunger pairs 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.

The first to use a direct injection engine stock car Mitsubishi. Therefore, consider the device and principles of operation direct injection on 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 for traditional injection engines with distributed injection, the ratio 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 GDI engine the atomized fuel is in the cylinder in the form of a cloud concentrated in the area of 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 cools - the filling of the cylinders improves somewhat, and the likelihood of detonation again decreases.

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 with constant speed(up to 120 km/h). Fuel is injected in a compact jet at the end of the compression stroke in the direction of the piston, reflected from it, mixed with air and evaporated, heading to the zone. 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 posed a new problem - the neutralization of exhaust 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 are 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 "mode homogeneous mixture formation"Used for heavy urban driving, high-speed suburban traffic and overtaking. Fuel is injected during 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 compression stroke, a compact jet of fuel is delivered, which brings the air-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 not inherent in high speeds traffic and constant traffic jams, and Europe is long autobahns and high speeds (and therefore 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. Main principle the 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 modes motor work. But such fuel systems also have differences, and sometimes quite significant ones. The main ones are the working pressure in fuel system, the location of the nozzles and their design.

many owners modern cars ask the question: “How does an injection engine work?”. Ignorance of this issue occurs, firstly, due to the fact that not all car owners studied physics well at school (at physics lessons, the device and principle of operation of an internal combustion engine are considered)

And secondly, in our time it is not necessary to know the car thoroughly in order to comfortably ride it - in the event of a breakdown, you can always give it to the service. However, there are still interested motorists who want to know as much as possible about their car, and our article is intended just for such.

How does an injection engine work? First of all, it is worth noting that the injection is one of the types of internal combustion engine that has become a genuine technical revolution. We begin our story with the device and principle of operation of an internal combustion engine.

History of creation and principle of operation of internal combustion engines

An internal combustion engine is an engine in which the combustion of fuel, due to which energy is released, occurs directly in it.

Most common today four-stroke engines who work on following scheme: first, the air-fuel mixture is admitted, then it is compressed, then the piston stroke follows, and the last stage is the release of the gases resulting from combustion.

Since only the third stroke (stroke of the piston) is working in an internal combustion engine, manufacturers of such power units include several cylinders (usually 4, ), cylinders adjacent to each other work with a lag of one cycle to provide permanent job engine.

Carburetor

In order for the internal combustion engine to receive digestible for work fuel-air mixture, the engineers had to come up with special device, which would prepare such a mixture right during the movement and transfer it to the engine. And such a device was invented - it became a carburetor.

Carburetor engines for quite a long time occupied a leading position in the engine market, until manufacturers began to think about the environment, and then it turned out that carburetor engines pollute the environment very much, and the power was low, which means that it is necessary to develop in principle new way supply of the fuel-air mixture.

Injector

The injector is one of the inventions that dramatically changed the entire automotive industry. Unlike a carburetor, which prepared the air-fuel mixture outside the engine, with an injection system, fuel is injected directly into the cylinders, which increases power (injected engines are about 10% more powerful than carbureted ones).

IN in general terms The principle of operation of an injection engine can be described as follows: fuel is injected through nozzles either into the manifold, where fuel and air are mixed, or, as on most modern cars, directly into the combustion chamber. Modern injection engines are divided into two types:

Single injection- all fuel is injected through common nozzles, and then distributed over the combustion chambers;
Engines with port injection- each piston has its own nozzle through which fuel enters it, mixing fuel with air in this case occurs just before combustion.

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 the maximum possible engine power, the composition of the mixture was adjusted so 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.

Due to the significant vacuum in the intake pipe, little air is drawn into the cylinders, the pressure in the combustion chamber remains relatively low at the end of the compression stroke, the process of burning an excessively rich mixture is slow, and there is a lot of unburned fuel 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 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.
reduction of toxicity of 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 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 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. The configuration of sensors on various vehicles depends 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 in the intake manifold for all cylinders), multi-point or distributed (each cylinder has its own nozzle that supplies fuel to the manifold) and direct ( fuel is supplied by injectors directly into the cylinders, as in 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 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 driving quietly at low speeds); 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 high-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 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 of wear, the operating pressure of the pump decreases and the quality of gasoline atomization 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:

Fuel pump high pressure(TNVD). Mechanical pump (similar diesel injection pump engine) develops a pressure of 50 bar (for 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 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.

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, which brings the ratio of air and fuel 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.

Implementation in the automotive industry began with the second half of the twentieth century and used an injector on a Goliath GP700 Sport car in 1951. The mass use of the injection system began in the automotive industry in the 80s.

Computerization and the introduction of electronic systems into the automotive industry did not go unnoticed for the injector either. Currently none modern plant does not produce injection engines without an electronic system called an electronic control unit (ECU), electronic system engine control (ECM) or controller, they are all one device, in the common people they are called "brains". Based on the foregoing, the injector can be characterized as follows - it is a fuel supply system controlled by brains, which, based on the data received from information devices (sensors), adjust the dose, moment and frequency of injection. From this definition it follows that the ECU is one of the main components of the injector. Below we will look at systems controlled by the controller and the sensors from which the data comes.
What are the advantages of the injection system over the carburetor:

reducing fuel consumption (implementation of hydrocarbon emission requirements), which mainly prompted automakers;
power increase at equal ICE volumes(approximately 10%);
automatic adjustment of the injection system. If anyone remembers in the carburetor this function was performed by suction, adjusting screws, etc.

What classifications of the injection system are:

1. Single injection (central injection, or single point injection) - where one nozzle supplies the intake tract (collector) to all cylinders located in the place of the carburetor. Commonly referred to as " electronic carburetor". Now you will meet him only on fairly old machines.
2. Distributed injection ( multipoint injection) i.e. a separate nozzle is installed during intake tract each cylinder or directly supplies fuel to the combustion chamber.

In its turn distributed injection divided by:
1) Simultaneous. For one turn crankshaft all injectors fire at the same time. This injection system is rare.
2) Pairwise-parallel. For one revolution of the crankshaft, the nozzles work out in pairs, that is, each pair fires once per revolution. Like the previous classification, the injection system is rare, but can be called, on a system with sequential injection, faulty sensor.
3) Phased or sequential. In one working cycle, each injector opens once just before the intake stroke and is adjusted separately. On this moment this type is produced by almost all auto manufacturers and it is the most massive. The difference between direct fuel injection and the above is that the injection occurs directly into the cylinder, where it is possible to control the phase and duration of the injection. The pressure of the nozzles of this system can reach 200 atmospheres.
The disadvantages of this system are:

high repair cost;
high cost of nodes;
low maintainability of elements;

Unlike its predecessors, given type injection leads to coking of the intake valve(s), due to not being washed by the fuel, which (s) in turn were cleaned by it.
The scheme of operation of the injector consists in supplying data to the controller from sensors (main):

Crankshaft sensor (DKV), informs the controller about the frequency, position and direction;
Mass air flow sensor (DMRV, volumemeter), designed to assess the amount of intake air and determine its temperature;
Coolant temperature sensor (DTOZH), serves to control the injection and ignition phase;
Throttle position sensor (TPS), designed to determine the load on the engine depending on the opening of the remote sensing, cylinder filling and speed;
The oxygen sensor in the exhaust gases (lambda probe) is designed to detect unburned hydrocarbon in the exhaust gas system and, as a result, the injection time changes and the ignition is corrected;
Knock sensor (DD), designed to detect knock;
Sensor camshaft(DRV) or Phase Sensor (DF), serves for precise synchronous injection. When the engine is in emergency mode or there is no such sensor, the system switches to pair-parallel (group) fuel supply;
The intake air temperature sensor can be installed separately, or directly integrated into the MAF.

Based on the data received from information sensors, the ECU controls the following systems (main):

nozzles - designed for fuel injection;
electric fuel pump - serves to form pressure in the fuel supply system;
ignition module (MZ) - designed for sparking on a candle. Recently, each candle has its own MZ;
idle speed controller (IAC or XX) is designed to maintain the set speed XX;
fan of the engine cooling system, controlled by DTOZH signals.

The disadvantages of the injection system is: low maintainability;

demand for fuel;
necessity special equipment to determine the malfunction;
high cost of elements (not for each type of injector).
Only a specialist can accurately determine the malfunction and diagnose the injection engine.

The main problem of injection engines is the failure of sensors, which is solved by replacement. On the example of a mass air flow sensor (DMRV), symptoms of a malfunction:
signal lamp about engine malfunction;
weak dynamics; floating engine speed at idle;
inability to start hot engine.
You can check the serviceability (DMRV) in several ways:
diagnostic equipment;
Shutdown (DMRV). In this case, the engine management system starts to work in emergency mode;
Replacement with a known-good one;
visual inspection.

Transition from carburetor system the fuel supply to the injection turned out to be more than successful, although this system has drawbacks. If there is a choice between an injector and a carburetor, I will definitely answer, choose the first. When choosing between sequential and direct, I personally choose sequential injection, because of the fewer problems.

It is very difficult to answer the question of how each driver chooses a car for himself. Everyone has their own evaluation criteria: someone focuses on their wealth, someone prefers specific brand cars, and someone is tightly tied to certain systems of the car.

So, many, even when buying a used car, still tend to choose those models on which a mechanical injector is installed. This system can be described in different ways. For some, it is the easiest, but for someone the most problematic. But in order to make such assessments, it is necessary to familiarize yourself with this device in great detail, which is what we are going to do in today's article.

1. Types of mechanical injectors that are still found on older car models.

Most famous car, which used to have a mechanical injector, today is the Audi 100. Like any fuel system, this device is designed to ensure an uninterrupted supply of the fuel-air mixture to the engine combustion chamber. Both forced injection of fuel into cylinders and monitoring parameters combustible mixture and the formation of this mixture in the device is monitored solely by mechanical devices. Only on some car models, a mechanical injector is combined with electrical signals, but often it is devoid of any electronics.

In short, a mechanical injector is a device in the fuel system of a car that is responsible for supplying fuel to the engine cylinders. In order for the engine to work correctly, the fuel, or rather, the fuel-air mixture, must constantly burn out. To do this, you need to observe the correct proportions of the ratio of gasoline and air. This is exactly what the mechanical injector provides: thanks to the non-stop atomization of the fuel, it can be mixed with air in optimal proportions. The spraying process is carried out in such a system thanks to nozzles.

However, mechanical injectors have long since left the assembly line, and they have been replaced by electronic devices. How do they differ from each other? The main difference is the force that causes the nozzles to open and spray fuel. In the mechanical version, this is due to the pressure that is specially created in the system, and in electronic injector opened by an electronic impulse. This is where the downside comes in. mechanical devices: engine speed in such cars directly depends on how much pressure is held in the fuel system. Essentially, for management mechanical nozzles the dispenser of the mechanical injector responds.

Electronic injector - more smart device, because the car's electronic control unit "knows" the opening and closing of the nozzles. But still, over time, mechanical injectors began to be equipped with electronics. In particular, special sensors can be installed to control and adjust the fuel supply to the injectors, focusing no longer on the pressure in the fuel system, but on the readings of the temperature and exhaust gas sensors.

Also, the composition of the combustible mixture itself can be adjusted based on the position of the accelerator pedal. But in any case, it is pressure that is the main factor that ensures the performance of a mechanical injector. This indicator can be in the range of 4-6.5 atmospheres.

Mechanical injectors can be presented in different versions. Like any other device, it has been repeatedly improved and changed in design. Naturally, all the changes were aimed only at making the device as good and practical as possible. But the types of mechanical injectors are not so diverse, and there are only three of them:

K-Jetronic.

The first one on the list is the first full-fledged mechanical injector, which began to be actively used in the design of cars. It is on the example of K-Jetronic that we will talk a little lower about the device of a mechanical injector, since all other types were somehow created on its basis and differ little.

2. The principle of operation of a mechanical injector of a car.

Before devoting you to the basic intricacies of the functioning of a mechanical injector, you should pay your attention to another name for this device - mono injection. He was the first to replace carburetor engines, and only later, when they began to modify and improve it, this device began to be called a mechanical injector. But more to the point.

Mechanical injectors are used only on those engines that run on gasoline. The basis of such a system is a nozzle that opens under pressure in the fuel system. But not less important element This device is also a throttle valve. It is thanks to it that the air supply to the combustion chamber is dosed, which allows you to create an optimal fuel-air mixture and ensure stable work engine.

In general, the principle of operation of a mechanical injector is very much criticized. The main reason it was discontinued is that cars with such a device pollute the environment too much. Since exhaust gas standards are very strictly controlled abroad, mono-injection has essentially become prohibited. However, with the correct setting of all elements, such an injector can work in accordance with all environmental regulations. In particular, it is very important that the throttle opening angle is correctly related to the engine speed.

The main factors on which the functioning of a mechanical injector depends are as follows:

The ratio between the volume of air flow and its mass;

Throttle opening angle;

An indicator of pressure in the fuel system of a car.

3. The device of a mechanical injector of a car: the main constituent elements and their characteristics.

As mentioned above, we want to talk about the design of a mechanical injector using an example K-Jetronic. You can get to know her personally on Audi 100 cars. In order for you to have a complete idea of both the work and the device of a mechanical injector, we will tell you in detail about each of its elements.

This element of a mechanical injector is a combination of chambers and a plunger. It is thanks to them that the regulation of the amount of gasoline that is supplied to the engine cylinders is carried out. Direct adjustment is carried out due to the degree of opening of the valves of each chamber.

Also, special tubes depart from each chamber to the injector nozzles. As the throttle opening angle increases, the vacuum increases in parallel, which raises the pressure plate. Since it is connected to the plunger by a lever, the plunger also rises. All this leads to the fact that the valve of each chamber opens and gasoline is supplied.

It is easy to conclude that the amount of gasoline burned in such a system directly depends on how much air is consumed to create an air-fuel mixture. And the air flow changes due to the rotation of the throttle, which is controlled through the accelerator pedal.

Temperature switch

This element is presented in the form of a bimetallic plate. Under the influence of temperature, that is, as a result of heating, it has the ability to deform. When it starts cold engine, the relay contact is in the closed position. Due to this, a current can pass through it, which in turn acts on the nozzle valve and further enriches the air-fuel mixture. However, under the influence of current, the temperature relay heats up, which ultimately leads to opening of the relay contact and turning off the nozzle.

Quality screw

In order for the car engine to work correctly and smoothly, the ratio of gasoline and air in the combustible mixture must comply with strict standards. It is precisely this norm that regulates such an element as a quality screw. If it does not work properly, then fuel consumption can increase significantly. This screw is in constant rotation, due to which it is possible to change the height of the plunger, as well as the flow area of the valves of all distribution chambers of the mechanical injector. This screw is located between the plunger rod and the flow meter lever.

Quantity screw (adjustment screw)

When the engine is idling, the driver does not press the gas pedal, which keeps the throttle closed. From all this it follows that air does not enter the combustion chamber of the engine through the usual channel, which means that an additional one is needed. The role of such is performed by the idle channel, which is created thanks to the adjusting screw. In addition, with the help of a screw, the quantities can be changed idling car engine with a mechanical injector. However, without special need to indulge in this screw is not recommended.

Essentially, this main element any injection system. The number of injectors strictly corresponds to the number of engine cylinders, since there is one injector for each cylinder. They are installed on the cylinders in such a way as to prevent the formation of plugs and at the same time provide thermal insulation.

If we talk about the Audi 100 car, then the nozzle on its engine is made in the form of a mechanical valve. The principle of its operation is quite simple: in order to get into the cylinder, gasoline has to overcome the force of the spring, which presses the nozzle valve. The force of the spring is selected specifically so that the nozzle opens only when the pressure level reaches 3.5 atmospheres.

In this case, fuel injection is carried out periodically. How is this possible? Just in the upper chambers of the distributor, short-term pressure drops are constantly formed, which causes interruptions in the operation of the nozzles. If the system is working, then each nozzle fires at the same pressure level.

Back pressure regulator

The operation of this device is based on lowering the back pressure that occurs in the distributor. Due to this, the valves from the chambers open, and more fuel enters. It is important to note that the distributor chambers are separated by a membrane and are classified as upper and lower. In the lower chambers, pressure is created using a pump, which, together with a spring, closes the valves. If the pressure will drop, then the membrane will fall down, which will lead to the opening of the valves.

Elements that maintain pressure in the vehicle's fuel system

These are devices that, in fact, are not entirely related to the design of the mechanical injector itself. This is a battery and a pressure regulator in the fuel system, injector valves and a gasoline pump. The first of them maintains the pressure on required level after the hot engine has been stopped. This lasts for a short period of time and is necessary in order to prevent the formation of traffic jams.

As for, it independently regulates the pressure with the help of two valves: safety and throughput. The opening of the bypass valve is provoked by the achievement of the working pressure value, and the throughput valve opens only when the pressure becomes very high. The nozzle valves are only able to hold pressure if it is below 3.5 atmospheres.

Starting nozzle

To start a cold engine with a mechanical injector, an additional portion of gasoline is supplied to the Audi 100 using an electromagnetic starting nozzle. It is turned on with closed contacts temperature relay. It turns off when the relay heats up and its contacts open. Also, the temperature switch can include an additional counter-pressure valve.

The starter nozzle is installed directly in front of throttle valve and the main elements of the injector. During normal operation of the engine, it is in the closed state, which is possible due to the presence of a spring. That's the whole device of a mechanical injector. In general, it is not at all difficult, however, without electrical supply system performance is not ideal.

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