Fuel injection systems for gasoline engines. Fuel injection systems of modern internal combustion engines: gasoline and diesel systems

26.06.2020

Miscellaneous

The main disadvantage of vehicles equipped with gasoline engines with a carburetor is that the fuel in them does not burn completely. Since the environmental friendliness, power, efficiency of the machine are determined by the performance characteristics of the fuel supply, there is a need for devices that regulate this process, focusing on the mode of operation.

Such nodes are called injection systems. In injection engines, fuel is supplied at a predetermined time in a given dosage. Fuel injection systems of various designs have been developed for gasoline and diesel engines.

Classification and arrangement of injection systems

Differences in injection mechanisms are determined by the method used to make a mixture of gasoline with air.

The classification is mainly carried out according to the type of injection:

central injection;
distributive;
direct;
combined.

Central injection (single injection)

This system replaces the carburetor, works on one nozzle. Single injection is almost never used due to non-compliance with environmental standards, found on very old cars. But these mechanisms are simple and reliable due to the location of the nozzle in place with good air exchange, in the intake manifold.

Elements of a monosystem:

pressure regulator - prevents the formation of air pockets, provides a constant pressure of 0.1 MPa;
nozzle - provides gasoline to the manifold;
throttle valve (mechanical, electric) - regulates the air supply;
control unit (memory, microprocessor) - contains information necessary for injection;
temperature sensors, the state of the crankshaft, throttle.

This type is more modern and environmentally friendly. Although, the only distinguishing feature is that in this system each cylinder already has its own nozzle. Only it is also mounted in the intake manifold, only each in its own separate pipe. Electronic systems control the dosage of fuel. The most advanced nozzles in this regard belong to Bosch.

direct injection

Gasoline simultaneously with air is supplied directly to the combustion chambers. The advantage of a direct injection system is the accurate calculation of the components for the fuel mixture. The percentage of environmentally hazardous emissions is reduced due to almost one hundred percent combustion of the fuel mixture.

Mechanism device with direct injection:

pump supplying gasoline;
pressure control device;
ramp equipped with a safety valve;
a sensor that displays pressure parameters;
nozzles.

Flaws:

high requirements for the quality composition of the fuel;
complex design for manufacturers;
the need for a pressure of 5 MPa.

But injection systems of this type are the most modern, promising.

Combined injection

To reduce emissions and meet Euro 6 requirements, Volkswagen has developed a combined injection system that combines distribution with direct injection. The systems are activated by the control unit in turn, focusing on the mode of operation. This power system is the most promising in terms of environmental safety.

The combined device consists of:

fuel supply pump;
details of the direct mechanism (injectors installed in the combustion chambers, a ramp maintaining a pressure of 20 MPa);
elements of the distribution system (injectors installed in the collector channels, low pressure ramps).

Principle of operation

Injection engine units with a single nozzle operate according to the scheme:

the motor starts;
sensors read and transmit information to the control unit;
real data are compared with the reference ones, the moment of nozzle opening is calculated;
a signal is transmitted to the electromagnetic coil;
gasoline is supplied to the manifold for mixing with air;
fuel mixture is supplied to the cylinders.

The functioning of the unit with distributed injection:

the motor is supplied with air;
sensors determine volume, temperature, crankshaft performance, damper position;
the amount of fuel for the supplied air is calculated by the control unit;
the injectors are signaled;
they open at the programmed time.
mixing of gasoline with air occurs in the manifold, the mixture is fed into the cylinders.

Training video of the principle of operation of distributed injection

The operating principle of direct injection depends on method of mixing gasoline with air:

in layers;
stoichiometrically;
homogeneous.

Layered mixing is used at medium speed, the air supply rate is high, gasoline is supplied to the cylinder through the nozzle, it lights up after mixing with air.

When mixing stoichiometric type, the process starts at the moment you press the gas. The throttle valve opens, gasoline and air are supplied at the same time, they burn completely.

When mixing homogeneous type, first air movement is created in the cylinders, then gasoline is injected.

Video explanation on the principle of operation of the direct injection injector

The operation of the combined system depends entirely on the load on the motor:

direct injection starts during start-up, warm-up, maximum load, the number of injections depends on the mode;
distributed injection starts while driving at medium speed with frequent stops.

With distributed injection, direct nozzles are periodically opened. This prevents them from clogging.

Injection systems are equipped not only with gasoline, but also with diesel engines. The first can be called spark engines, since the mixture of gasoline and air is ignited by a spark.

Main malfunctions

Most often, injection failures are manifested by several malfunctions:

the motor does not start (the main relay is faulty, the pump does not work, there is no voltage on the injectors);
the cold engine is unstable (the temperature sensor is faulty);
the motor does not work well at the transitions (the pump or nozzle is faulty);
the engine stalls (the fuel system is out of order, the air inlet is depressurized).

Advantages and disadvantages

Here, as in any system, there are advantages and disadvantages.

Advantages of injectors (when compared with a carburetor):

reduction of fuel consumption by 2 times;
increase in power;
simplified (automated) launch;
easy control;
reducing the release of toxins several times;
self-tuning, which simplifies maintenance;
repair is reduced to the replacement of parts;
reducing the height of the hood due to the placement of injection elements on the sides of the motor;
independence from the pressure of the atmosphere, the position of the car (the work of carburetors is disturbed during rolls).

Cons of injection systems:

relatively high production cost;
high requirements for the quality of gasoline;
the need for special equipment for diagnostics;
dependence on electricity;
increasing the likelihood of a fire in an accident due to the supply of gasoline under pressure.

The last drawback is partially offset by the installation of a controller that turns off the feed on impact.

Several types of injection systems made it possible to equip them with most passenger cars produced after the eighties. Mechanical or electronic control, fuel can be supplied continuously or in pulses.

Regardless of the structure and principle of operation of the fuel injection system, it will last longer without repair if you refuse to manipulate the power supply, do not turn off the ground unnecessarily, and do not start by towing. Injector systems do not tolerate moisture, if water penetrates into them in winter, there is a high probability of failure of the nozzles. The fuel must be clean, special attention should be paid to the condition of the filter installed in front of the pump. If there are impurities in the fuel, the pump and control system fail very soon.

The fuel injection system is used to metered fuel supply to the internal combustion engine at a strictly defined point in time. Power, efficiency and depend on the characteristics of this system. Injection systems can have different designs and versions, which characterizes their efficiency and scope.

Brief history of appearance

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

The first injection system was almost completely mechanical and was characterized by low efficiency. The reason for this was the insufficient level of technological progress, which could not fully reveal its 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 the percentage of the 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 the presence of one, 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 working pressure of 0.1 MPa and prevents the appearance of air pockets in.
Injection nozzle - performs a pulsed supply of gasoline to the engine intake manifold.
— regulates the volume of supplied air. May be mechanical or electrically driven.
Control unit - consists of a microprocessor and a memory unit that contains the reference data of the fuel injection characteristics.
Sensors for engine crankshaft position, throttle position, temperature, etc.

Gasoline injection systems with a single nozzle work 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 received data is compared with the reference characteristic, and, based on this information, the control unit calculates the moment and duration of the nozzle opening.
A signal is sent to the electromagnetic coil to open the nozzle, which leads to the supply of fuel to the intake manifold, where it mixes with air.
A mixture of fuel and air is supplied to the cylinders.

Multiport Injection (MPI)

A multiport injection system consists of similar elements, but in this design there are separate nozzles for each cylinder, which can be opened simultaneously, in pairs or one at a time. The mixing of air and gasoline also occurs in the intake manifold, but, unlike mono-injection, fuel is supplied only to the intake tracts of the corresponding cylinders.

Scheme of operation of the system with distributed injection

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

The principle of operation of distributed injection:

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

Direct fuel injection (GDI)

The system provides for the supply of gasoline by separate nozzles directly to 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 the engine operating mode. At the same time, the mixture burns out almost completely, thereby reducing the amount of harmful emissions into the atmosphere.

Diagram of the direct injection system

Such an injection system is complex and susceptible to fuel quality, making it expensive to manufacture and operate. Since the injectors operate in more aggressive conditions, for the correct operation of such a system, it is necessary to ensure 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 increase above the permissible level).
High pressure sensor.
Nozzles.

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

Layered - implemented at low and medium engine speeds. Air is fed into the combustion chamber at high speed. Fuel is injected towards and, mixing with air along the way, ignites.
Stoichiometric. When you press the gas pedal, the throttle opens and fuel is injected simultaneously with the air supply, after which the mixture ignites and burns completely.
Homogeneous. In the cylinders, intensive air movement is provoked, while gasoline is injected on the intake stroke.

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

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In this article, you will find all the essential information about a part of a road vehicle such as the fuel injection system. Start reading now!

In this article, you can easily find answers to such fairly common questions:

What is an injection system and how does it work?
The main types of injection schemes;
What is fuel injection, and what effect does it have on engine performance?

What is a fuel injection system and how does it work?

Modern cars are equipped with various systems for supplying gasoline. The fuel injection system, or as it is also called injector, provides the supply of a gasoline mixture. On modern engines, the injection system has completely replaced the carburetor power scheme. Despite this, among motorists to this day there is no single opinion about which one is better, because each of them has its own advantages and disadvantages. Before understanding the principle of operation and types of fuel injection systems, it is necessary to understand its elements. So, the fuel injection system consists of the following main elements:

Throttle valve;
Receiver;
Four nozzles;
Channel.

Now consider the principle of operation of the fuel supply system to the engine. The air supply is regulated by a throttle valve, and before being divided into four streams, it accumulates in the receiver. The receiver is needed for the correct calculation of the mass flow of air, because the measurement of the total mass flow or pressure in the receiver is carried out. The receiver must be of sufficient size in order to exclude the possibility of air starvation of the cylinders during high air consumption, as well as to smooth out the pulsation at start-up. Four nozzles are located in the channel in close proximity to the intake valves.

The fuel injection system is used on both gasoline and diesel engines. In addition, the design and operation of the gasoline supply of diesel and gasoline engines have significant differences. On gasoline engines, by means of the fuel supply, a homogeneous air-fuel mixture is formed, which is forcibly ignited by sparks. On diesel engines, the fuel mixture is supplied under high pressure, the dose of the fuel mixture is mixed with hot air and ignites almost immediately. The pressure determines the size of the portion of the injected fuel mixture, and hence the power of the engine. Therefore, engine power is directly proportional to pressure. That is, the greater the fuel supply pressure, the greater the engine power. The fuel mixture scheme is an integral part of the vehicle. The main working “body” of absolutely every injection scheme is the nozzle.

Fuel injection system on gasoline engines

Depending on the method of formation of the air-fuel mixture, such central injection systems are distinguished, direct and distributed type. The distributed and central injection system is a pre-injection scheme. That is, injection into them takes place without reaching the combustion chamber, which is located in the intake manifold.

Central injection (or mono injection) takes place using a single nozzle, which is installed in the intake manifold. To date, a system of this type is not produced, but is still found on passenger cars. This type is quite simple and reliable, but has increased fuel costs and low environmental performance.

Distributive fuel injection is the supply of a fuel mixture to the intake manifold through a separate fuel injector for each cylinder. An air-fuel mixture is formed in the intake manifold. It is the most common fuel injection scheme on gasoline engines. The first and main advantage of the distributed type is economy. In addition, due to more complete combustion of fuel in one cycle, cars with this type of injection do less harm to the environment with harmful emissions. With accurate dosing of the fuel mixture, the risk of unforeseen malfunctions in operation in extreme modes is reduced to almost zero. The disadvantage of this type of injection system is the rather complex and completely electronically dependent design. Due to the large number of components, repairs and diagnostics of this type are possible only in the conditions of an automotive service center.

One of the most promising types of fuel supply is a direct fuel injection system. The mixture is fed directly into the combustion chamber of all cylinders. The supply scheme makes it possible to create the optimal composition of the air-fuel mixture during the operation of all engine operating modes, increase the compression level, fuel economy, increase power, and also reduce harmful emissions. The disadvantage of this type of injection lies in the complex design, as well as high operational requirements. In order to reduce the level of particulate emissions into the atmosphere together with exhaust gases, combined injection is used, which combines the scheme of direct and distributed supply of gasoline on a single internal combustion engine.

Fuel injection into an engine can be electronically or mechanically controlled. The best is electronic control, which provides significant savings in the combustible mixture, as well as the reduction of harmful emissions. Injection of the fuel mixture in the scheme can be pulsed or continuous. The most promising and economical is pulsed injection of a combustible mixture, which uses all modern types. In an engine, this circuit is usually combined with ignition to form a combined fuel/ignition circuit. Coordination of the functioning of the fuel supply schemes is ensured by the engine control circuit.

We hope that this article has helped you find a solution to the problems and you have found answers to all questions that relate to this topic. Follow the rules of the road and be vigilant while traveling!

The direct fuel injection system in gasoline engines is by far the most advanced and modern solution. The main feature of direct injection can be considered that the fuel is supplied directly to the cylinders.

For this reason, this system is also often referred to as direct fuel injection. In this article, we will look at how a direct injection engine works, as well as what advantages and disadvantages such a scheme has.

Read in this article

Direct fuel injection: direct injection system device

As mentioned above, the fuel in these is supplied directly to the combustion chamber of the engine. This means that the injectors do not spray gasoline into, after which the fuel-air mixture enters through the cylinder, but directly inject fuel into the combustion chamber.

The first direct injection gasoline engines were . In the future, the scheme became widespread, as a result of which today with such a fuel supply system can be found in the lineup of many well-known automakers.

For example, the VAG concern introduced a number of Audi and Volkswagen models with naturally aspirated and turbocharged ones that received direct fuel injection. Direct injection engines are also produced by BMW, Ford, GM, Mercedes and many others.

Direct fuel injection has become so widespread due to the high efficiency of the system (about 10-15% compared to distributed injection), as well as more complete combustion of the working mixture in the cylinders and a decrease in exhaust gas toxicity.

Direct injection system: design features

So, let's take the FSI engine with its so-called "stratified" injection as an example. The system includes the following elements:

high pressure circuit;
gasoline;
pressure regulator;
fuel rail;
high pressure sensor;
injection nozzles;

Let's start with the fuel pump. The specified pump creates a high pressure under which fuel is supplied to the fuel rail, as well as to the injectors. The pump has plungers (there can be several plungers, or one in rotary pumps) and is driven by the inlet camshaft.

RTD (fuel pressure regulator) is integrated into the pump and is responsible for the metered fuel supply, which corresponds to the injector injection. A fuel rail (fuel rail) is needed in order to distribute fuel to the injectors. Also, the presence of this element allows you to avoid pressure surges (pulsations) of the fuel in the circuit.

By the way, the circuit uses a special safety valve, which is in the rail. This valve is needed in order to avoid too high fuel pressure and thus protect individual elements of the system. An increase in pressure can occur due to the fact that the fuel tends to expand when heated.

The high pressure sensor is a device that measures the pressure in the fuel rail. Signals from the sensor are transmitted to, which, in turn, is able to change the pressure in the fuel rail.

As for the injection nozzle, the element ensures the timely supply and atomization of fuel in the combustion chamber in order to create the necessary fuel-air mixture. Note that the processes described are controlled by . The system has a group of various sensors, an electronic control unit, as well as actuators.

If we talk about the direct injection system, together with the high fuel pressure sensor, the following are involved for its operation: , DPRV, air temperature sensor in the intake manifold, coolant temperature sensor, etc.

Thanks to the operation of these sensors, the necessary information is supplied to the ECU, after which the unit sends signals to the actuators. This allows you to achieve coordinated and accurate operation of solenoid valves, nozzles, a safety valve and a number of other elements.

How Direct Fuel Injection Works

The main advantage of direct injection is the ability to achieve various types of mixture formation. In other words, such a power supply system is able to flexibly change the composition of the working fuel-air mixture, taking into account the operating mode of the engine, its temperature, the load on the internal combustion engine, etc.

It is necessary to single out layer-by-layer mixing, stoichiometric, and also homogeneous. It is this mixture formation that ultimately makes it possible to use fuel as efficiently as possible. The mixture always turns out to be of high quality, regardless of the mode of operation of the internal combustion engine, gasoline burns out fully, the engine becomes more powerful, while exhaust toxicity is reduced at the same time.

Layered mixture formation is activated when the engine loads are low or medium, and the crankshaft speed is low. Simply put, in such modes, the mixture is somewhat leaner in order to save money. Stoichiometric mixing involves preparing a mixture that is highly flammable without being overly enriched.
Homogeneous mixture formation allows you to get the so-called "power" mixture, which is needed at high engine loads. On a lean homogeneous mixture, in order to further save money, the power unit operates in transient modes.
When stratification is engaged, the throttle is wide open with the intake flaps closed. Air is supplied to the combustion chamber at a high speed, turbulence of air flows occurs. Fuel is injected near the end of the compression stroke, injection is made in the area where the spark plug is located.

In the short time before a spark appears on the spark plug, a fuel-air mixture is formed in which the excess air ratio is 1.5-3. Next, the mixture is ignited by a spark, while a sufficient amount of air is retained around the ignition zone. This air acts as a thermal "insulator".

If we consider homogeneous stoichiometric mixture formation, such a process occurs when the intake flaps are open, while the throttle is also open at one angle or another (depending on the degree of pressing the accelerator pedal).

In this case, the fuel is injected even during the intake stroke, as a result of which it is possible to obtain a homogeneous mixture. Excess air has a coefficient close to unity. Such a mixture is highly flammable and fully burns throughout the entire volume of the combustion chamber.

A lean homogeneous mixture is created when the throttle is fully open and the intake flaps are closed. In this case, air is actively moving in the cylinder, and fuel injection falls on the intake stroke. The ECM maintains excess air at 1.5.

In addition to clean air, exhaust gases can be added. This is due to work. As a result, the exhaust “burns out” again in the cylinders without damage to the engine. At the same time, the level of emissions of harmful substances into the atmosphere is reduced.

What is the result

As you can see, direct injection allows you to achieve not only fuel economy, but also a good return on the engine in both low and medium, and high loads. In other words, the presence of direct injection means that the optimal composition of the mixture will be maintained in all modes of operation of the internal combustion engine.

As for the disadvantages, the disadvantages of direct injection can only be attributed to the increased complexity during repairs and the price of spare parts, as well as the high sensitivity of the system to fuel quality and the condition of fuel and air filters.

1. Features of the fuel injection system

On engines produced today, the carburetor system has not been used for a long time, which turned out to be completely superseded by a newer and improved fuel injection system. It is customary to call fuel injection a system for metered supply of fuel fluid to the cylinders of a vehicle engine. It can be installed on both gasoline and diesel engines, however, it is clear that the design and principle of operation will be different. When used on gasoline engines, when injected, a homogeneous air-fuel mixture appears, which is forced to ignite under the influence of a spark plug spark.

As for the diesel engine type, here the fuel is injected under very high pressure, and the required portion of the fuel is mixed with hot air and ignites almost immediately. The size of the portion of the injected fuel, and at the same time the total engine power, is determined by the injection pressure. Therefore, the greater the pressure, the higher the power of the power unit becomes.

Today, there is a fairly significant amount of species diversity of this system, and the main types include: a system with direct injection, with mono injection, mechanical and distributed systems.

The principle of operation of the direct (direct) fuel injection system is that the fuel liquid, using nozzles, is supplied directly to the engine cylinders (for example, like a diesel engine). For the first time such a scheme was used in military aviation during the Second World War and on some cars of the post-war period (the first was the Goliath GP700). However, the direct injection system of that time failed to gain due popularity, the reason for which was the expensive high-pressure fuel pumps required for operation and the original cylinder head.

As a result, the engineers did not manage to achieve working accuracy and reliability from the system. Only at the beginning of the 90s of the twentieth century, due to the tightening of environmental standards, interest in direct injection began to increase again. Among the first companies to launch the production of such engines were Mitsubishi, Mercedes-Benz, Peugeot-Citroen, Volkswagen, BMW.

In general, direct injection could be called the peak of the evolution of power systems, if not for one thing ... Such engines are very demanding in terms of fuel quality, and when using lean mixtures, they also strongly emit nitrogen oxide, which has to be dealt with by complicating the design of the motor .

Single-point injection (also called "mono-injection" or "central injection") - is a system that began to be used in the 80s of the twentieth century as an alternative to a carburetor, especially since the principles of their operation are very similar: air flows are mixed with the fuel liquid during intake manifold, but the nozzle came to replace the complex and sensitive to the settings of the carburetor. Of course, at the initial stage of development of the system, there were no electronics at all, and mechanical devices controlled the supply of gasoline. However, despite some shortcomings, the use of injection still provided the engine with much higher power ratings and significantly greater fuel efficiency.

And all thanks to the same nozzle, which made it possible to dose the fuel liquid much more accurately, spraying it into small particles. As a result of the mixture with air, a homogeneous mixture was obtained, and when the driving conditions of the car and the operating mode of the engine changed, its composition changed almost instantly. Admittedly, it wasn't without its downsides. For example, since, in most cases, the nozzle was installed in the body of the former carburetor, and bulky sensors made it difficult for the “motor to breathe”, the air flow entering the cylinder met with serious resistance. On the theoretical side, such a disadvantage could be easily eliminated, but with the existing poor distribution of the fuel mixture, no one could do anything then. This is probably why, in our time, single-point injection is so rare.

The mechanical injection system appeared in the late 1930s, when it began to be used in aircraft fuel supply systems. It was presented in the form of a gasoline injection system of diesel origin, using high-pressure fuel pumps and closed nozzles for each individual cylinder. When they tried to install them on a car, it turned out that they could not withstand the competition of carburetor mechanisms, and this was due to the significant complexity and high cost of the structure.

For the first time, a low-pressure injection system was installed on a MERSEDES car in 1949 and immediately outperformed a carburetor-type fuel system in terms of performance. This fact gave impetus to further development of the idea of gasoline injection for cars equipped with an internal combustion engine. From the point of view of pricing policy and reliability in operation, the most successful in this regard was the mechanical system "K-Jetronic" by BOSCH. Its mass production was launched back in 1951 and, almost immediately, it became widespread in almost all brands of European automobile manufacturers.

The multi-point (distributed) version of the fuel injection system differs from the previous ones in the presence of an individual nozzle, which was installed in the inlet pipe of each individual cylinder. Its task is to supply fuel directly to the intake valve, which means preparing the fuel mixture right before it enters the combustion chamber. Naturally, under such conditions, it will have a uniform composition and approximately the same quality in each of the cylinders. As a result, the engine power, its fuel efficiency is significantly increased, and the level of exhaust toxicity is also reduced.

On the way to the development of a system of distributed fuel injection, certain difficulties were sometimes encountered, however, it still continued to improve. At the initial stage, it was also controlled mechanically, like the previous version, however, the rapid development of electronics not only made it more efficient, but also gave it a chance to coordinate with the rest of the motor design components. So it turned out that a modern engine is able to signal a malfunction to the driver, if necessary, independently switch to emergency operating mode or, with the support of security systems, correct individual errors in control. But all this, the system performs with the help of certain sensors, which are designed to record the slightest changes in the activity of one or another part of it. Let's consider the main ones.

2. Sensors of the fuel injection system

The sensors of the fuel injection system are designed to capture and transmit information from the actuators to the engine control unit and vice versa. These include the following devices:

Its sensitive element is placed in the exhaust (exhaust) gas flow, and when the operating temperature reaches 360 degrees Celsius, the sensor begins to generate its own EMF, which is directly proportional to the amount of oxygen in the exhaust gases. From a practical standpoint, when the feedback loop is closed, the oxygen sensor signal is a rapidly changing voltage between 50 and 900 millivolts. The possibility of changing the voltage is caused by a constant change in the composition of the mixture near the stoichiometry point, and the sensor itself is not suitable for generating an alternating voltage.

Depending on the power supply, two types of sensors are distinguished: with pulsed and constant power supply to the heating element. In the pulse version, the oxygen sensor is heated by an electronic control unit. If it is not warmed up, then it will have a high internal resistance, which will not allow it to generate its own EMF, which means that the control unit will “see” only the indicated stable reference voltage. During the warm-up of the sensor, its internal resistance decreases and the process of generating its own voltage begins, which immediately becomes known to the ECU. For the control unit, this is a signal of readiness for use in order to adjust the composition of the mixture.

Used to get an estimate of the amount of air that enters the engine of a car. It is part of the electronic engine control system. This device can be used together with some other sensors, such as an air temperature sensor and an atmospheric pressure sensor, which correct its readings.

The air flow sensor consists of two platinum filaments heated by electric current. One thread passes air through itself (cooling in this way), and the second is a control element. With the help of the first platinum thread, the amount of air that has entered the engine is calculated.

Based on the information received from the air flow sensor, the ECU calculates the required amount of fuel required to maintain the stoichiometric ratio of air and fuel in the given engine operating modes. In addition, the electronic unit uses the received information to determine the regime point of the motor. To date, there are several different types of sensors responsible for air mass flow: for example, ultrasonic, vane (mechanical), hot-wire, etc.

Coolant temperature sensor (DTOZH). It has the form of a thermistor, that is, a resistor, in which the electrical resistance can vary depending on temperature indicators. The thermistor is located inside the sensor and expresses a negative coefficient of resistance of temperature indicators (with heating, the resistance force decreases).

Accordingly, at a high temperature of the coolant, a low resistance of the sensor is observed (approximately 70 ohms at 130 degrees Celsius), and at a low temperature, it is high (approximately 100800 ohms at -40 degrees Celsius). Like most other sensors, this device does not guarantee accurate results, which means that it is only possible to speak about the dependence of the resistance of the coolant temperature sensor on temperature indicators. In general, although the described device practically does not break, it is sometimes seriously “mistaken”.

. It is mounted on the throttle pipe and connected to the axis of the damper itself. It is presented in the form of a potentiometer with three ends: one is supplied with positive power (5V), and the other is connected to ground. The third pin (from the slider) sends the output signal to the controller. When the throttle is turned when the pedal is depressed, the output voltage of the sensor changes. If the throttle is in the closed state, then, accordingly, it is lower than 0.7 V, and when the damper starts to open, the voltage rises and in the fully open position should be more than 4 V. Following the output voltage of the sensor, the controller, depending on the angle throttle opening, performs fuel correction.

Given that the controller itself determines the minimum voltage of the device and takes it as a zero value, this mechanism does not need to be adjusted. According to some motorists, the throttle position sensor (if it is domestically produced) is the most unreliable element of the system, requiring periodic replacement (often after 20 kilometers). Everything would be fine, but it’s not so easy to make a replacement, especially without having a high-quality tool with you. It's all about fastening: the bottom screw is unlikely to be unscrewed with a conventional screwdriver, and if it does, it is rather difficult to do so.

In addition, when tightening at the factory, the screws are “planted” on a sealant, which “seals” so much that the cap often breaks off when unscrewed. In this case, it is recommended to completely remove the entire throttle assembly, and in the worst case, you will have to pick it out by force, but only if you are completely sure that it is not in working condition.

. Serves to transmit a signal to the controller about the speed and position of the crankshaft. Such a signal is a series of repeated voltage pulses that are generated by the sensor during the rotation of the crankshaft. Based on the received data, the controller can control the injectors and the ignition system. The crankshaft position sensor is mounted on the oil pump cover, at a distance of one millimeter (+0.4mm) from the crankshaft pulley (has 58 teeth arranged in a circle).

To enable the generation of a “synchronization pulse”, two pulley teeth are missing, that is, in fact, there are 56 of them. When it rotates, the teeth of the disk change the magnetic field of the sensor, thereby creating an impulse voltage. Based on the nature of the pulse signal coming from the sensor, the controller can determine the position and speed of the crankshaft, which allows you to calculate the moment of operation of the ignition module and injectors.

The crankshaft position sensor is the most important of all those listed here, and in the event of a malfunction of the mechanism, the car's engine will not work. Speed sensor. The principle of operation of this device is based on the Hall effect. The essence of his work is to transfer voltage pulses to the controller, with a frequency directly proportional to the speed of rotation of the driving wheels of the vehicle. Based on the connectors of the harness block, all speed sensors may have some differences. So, for example, a square-shaped connector is used in Bosch systems, and a round connector corresponds to January 4 and GM systems.

Based on the outgoing speed sensor signals, the control system can determine the fuel cutoff thresholds, as well as set the vehicle's electronic speed limits (available in new systems).

Camshaft position sensor(or as I also call it a "phase sensor") is a device designed to determine the angle of the camshaft and transmit the relevant information to the vehicle's electronic control unit. After that, based on the data received, the controller can control the ignition system and the fuel supply to each individual cylinder, which, in fact, he does.

Knock sensor used to search for detonation shocks in an internal combustion engine. From a constructive point of view, it is a piezoceramic plate enclosed in a housing, located on the cylinder block. Nowadays, there are two types of knock sensor - resonant and more modern broadband. In resonant models, the primary filtering of the signal spectrum is carried out inside the device itself and directly depends on its design. Therefore, on different types of engine, different models of knock sensors are used, which differ from each other in resonant frequency. The broadband view of the sensors has a flat characteristic in the range of detonation noise, and the signal is filtered by the electronic control unit. Today, resonant knock sensors are no longer installed on production car models.

Absolute pressure sensor. Provides tracking of changes in barometric pressure that occur as a result of changes in barometric pressure and/or changes in altitude. The barometric pressure can be measured during ignition on, before the engine starts to crank. With the help of the electronic control unit, it is possible to "update" the barometric pressure data with the engine running, when, at a low engine speed, the throttle is almost fully open.

Also, using an absolute pressure sensor, it is possible to measure the change in pressure in the intake pipe. Changes in pressure are caused by changes in engine loads and crankshaft speed. The absolute pressure sensor transforms them into an output signal having a certain voltage. When the throttle is in the closed position, the absolute pressure output signal is relatively low voltage, while the wide open throttle is high voltage. The appearance of a high output voltage is explained by the correspondence between atmospheric pressure and the pressure inside the intake pipe at full throttle. The internal pressure of the pipe is calculated by the electronic control unit based on the sensor signal. If it turned out that it is high, then an increased supply of fuel fluid is required, and if the pressure is low, then vice versa - reduced.

(ECU). Although this is not a sensor, but given that it is directly related to the operation of the described devices, we considered it necessary to include it in this list. The ECU is the “think tank” of the fuel injection system, which constantly processes information data received from various sensors and, on the basis of this, controls the output circuits (electronic ignition systems, injectors, idle speed controller, various relays). The control unit is equipped with a built-in diagnostic system capable of recognizing malfunctions in the system and, using the “CHECK ENGINE” warning lamp, warn the driver about them. What's more, it stores diagnostic codes in its memory that indicate specific areas of failure, making it much easier to carry out repairs.

The ECU contains three types of memory: programmable read-only memory (RAM and PROM), random access memory (RAM or RAM), and electrically programmable memory (EPROM or EEPROM). RAM is used by the unit's microprocessor for temporary storage of measurement results, calculations and intermediate data. This type of memory depends on energy supply, which means that it requires a constant and stable power supply to store information. In the event of a power failure, all diagnostic trouble codes and calculation information stored in RAM are immediately erased.

The EPROM stores the general operating program, which contains the sequence of necessary commands and various calibration information. Unlike the previous version, this type of memory is not volatile. The EPROM is used to temporarily store the immobilizer (anti-theft vehicle system) password codes. After the controller has received these codes from the immobilizer control unit (if any), they are compared with those already stored in the EEPROM, and then a decision is made to allow or prohibit the engine from starting.

3. Actuators of the injection system

The actuators of the fuel injection system are presented in the form of a nozzle, a gasoline pump, an ignition module, an idle speed controller, a cooling fan, a fuel consumption signal and an adsorber. Let's consider each of them in more detail. Nozzle. Acts as a solenoid valve with a normalized capacity. It is used to inject a certain amount of fuel calculated for a specific operating mode.

Gasoline pump. It is used to transfer fuel to the fuel rail, the pressure in which is maintained by a vacuum-mechanical pressure regulator. In some system variants, it can be combined with a gasoline pump.

ignition module is an electronic device designed to control the process of sparking. It consists of two independent channels for setting fire to the mixture in the engine cylinders. In the latest, modified versions of the device, its low-voltage elements are defined in the computer, and in order to obtain high voltage, either a two-channel remote ignition coil is used, or those coils that are located directly on the candle itself.

Idling regulator. Its task is to maintain the set speed in idle mode. The regulator is presented in the form of a stepper motor that controls the air bypass channel in the throttle body. This provides the motor with the airflow it needs to run, especially when the throttle is closed. The fan of the cooling system, as the name implies, does not allow overheating of parts. Controlled by the ECU, which responds to the signals of the coolant temperature sensor. As a rule, the difference between the on and off positions is 4-5°C.

Fuel consumption signal- enters the trip computer in the ratio of 16,000 pulses per 1 calculated liter of fuel used. Of course, these are only approximate data, because they are calculated based on the total time spent opening the nozzles. In addition, a certain empirical coefficient is taken into account, which is needed to compensate for the assumption in the measurement of the error. Inaccuracies in the calculations are caused by the operation of the injectors in the non-linear section of the range, non-synchronous fuel output and some other factors.

Adsorber. It exists as an element of a closed circuit during the recirculation of gasoline vapors. Euro-2 standards exclude the possibility of contact between the ventilation of the gas tank and the atmosphere, and gasoline vapors must be adsorbed and sent for afterburning during the purge.