injection systems. Fuel supply system

Internal combustion (ICE) is based on the combustion of a small amount of fuel in a limited volume. In this case, the released energy is converted due to the movement of the pistons into mechanical energy. The metered amount of fuel is provided by a carburetor or a special device - an injector. Engines with such devices are called injection engines. The working principle of the injection engine is simple - supply to right moment time of the right amount of fuel to the right place.

How ICE works

In order to clearly understand the difference between the two types of power devices, it is necessary to first touch on how an internal combustion engine generally works. There are several different types, of which the most common are:

1. gasoline;
2. diesel;
3. gas-diesel;
4. gas;
5. rotary.

The principle of operation of the motor can best be understood with an example. gasoline engine. The most popular of them is the four-stroke. This means that the entire cycle of converting the energy generated during the combustion of fuel into mechanical energy is carried out in four cycles.
The design of the engine is such that the sequence of cycles is as follows:

• intake - filling the cylinders with fuel:
• compression - preparation of fuel for combustion;
• working stroke - conversion of combustion energy into mechanical;
• release - removal of fuel combustion products.

To ensure the operation of the engine, each of them has its own task. During the first stroke, the piston descends from top position to the lowest, the valve (inlet) opens and the cylinder begins to fill with a fuel-air mixture. In the second stroke, the valves are closed, and the piston moves from the lower position to the upper one, the mixture in the cylinder is compressed. When it reaches the top position, a spark jumps on the candle and the mixture is ignited.

When it burns, an increased pressure is formed, which causes the piston to move from the upper position to the lower one. After reaching it, under the action of the inertia of the rotation of the crankshaft, the piston begins to move up again, and the Exhaust valve, the products of combustion of fuel are brought out of the cylinder. When the piston reaches its upper position, the exhaust valve closes, but the intake valve opens and the entire cycle of operation is repeated.

All of the above can be seen in the video.

About the carburetor, its advantages and disadvantages

Here it is necessary to make a small addition. Since we are considering a gasoline engine, then it is possible to supply gasoline to the engine cylinders different ways. Historically, the first to be developed was the supply and dosage of gasoline using a carburetor. This is a special device that provides required amount fuel-air mixture(TVS) in cylinders.


Fuel-air is a mixture of air and gasoline vapor. It's cooked in a carburetor special device, for mixing them in the right proportion, depending on the mode of operation of the engine. Being quite simple in its design, the carburetor worked successfully with a gasoline engine for a long time.
However, as the car developed, shortcomings were revealed that, in the conditions prevailing by that time, it was already difficult for engine developers to put up with. This primarily concerned:

• fuel economy. The carburetor did not provide economical consumption of gasoline in case of a sudden change in the mode of movement of the car;
• environmental safety. The content of toxic substances in the exhaust gases was quite high;
• insufficient engine power due to the mismatch of fuel assemblies with the mode of movement of the vehicle and its current state.

To get rid of the noted shortcomings, a different principle was implemented for supplying fuel to the engine - using an injector.

About injection engines

They have another name - injection engines, which, in general, in no way changes the essence of the phenomena taking place. According to the work performed, injection resembles the principle implemented in the operation of a diesel engine. A strictly metered amount of fuel is injected into the engine at the right time through the injector nozzles, and it is ignited by a spark from a candle, although a candle is not used during diesel operation.


The entire cycle of the four-stroke internal combustion engine, discussed earlier, remains unchanged. The main difference is that the carburetor prepares fuel assemblies outside the engine, and then it enters the cylinders, while in the latest injection engines, gasoline is injected directly into the cylinder.

How this happens can be seen in detail in the video.

Such a motor device allows you to solve the problems that arise during the operation of the carburetor. The use of an injector provides compared to the carburetor option the following benefits motor:

• power increase by 7-10%;
• improvement of indicators of fuel profitability;
• reduction of the level of toxic substances in the composition of exhaust gases;
• ensuring the optimal amount of fuel, depending on the mode of movement of the car.

These are just the main advantages that an injection engine allows you to get. However, each advantage has its drawbacks. If the carburetor motor is purely mechanical and can be repaired in almost any conditions, then injection requires complex electronics and a whole system of sensors, which is why work (regulation and repair) must be carried out in a service center.

injection device

If you look at what it looks like internal combustion engine device with injection instead of a carburetor, we can distinguish:

• injection controller - electronic device, containing a program for the operation of all the components of the system;
• nozzles. They can be either several or one, depending on the injection system used;
• an air flow sensor that determines the filling of the cylinders depending on the stroke. First, the total consumption is determined, and then the required amount for each cylinder is recalculated programmatically;
• sensor throttle valve(its position), which sets the current state of movement and the load on the engine;
• a temperature sensor that controls the degree of heating of the coolant, according to its data, the operation of the engine is corrected and, if necessary, the operation of the blower fan begins;
• actual location sensor crankshaft ensuring the synchronization of the operation of all components of the system;
• an oxygen sensor that determines its content in the exhaust gases;
• a knock sensor that controls the occurrence of the latter; to eliminate it, the value of the ignition timing changes according to its signals.

This is what a system that provides fuel injection looks like in general terms, the principle of operation should be quite clear from its composition and the purpose of individual elements.

Types of injection systems

Despite the rather simple description of the operation of the injection motor given earlier, there are several varieties that carry out similar principle work.

single point injection

This is the simplest implementation of the injection principle. It is practically compatible with any carbureted engine, the difference being injection instead of carburetor. If the carburetor intake manifold supplies fuel assemblies, then with single-point injection, gasoline is injected into the intake manifold through the nozzle.

As in the case with carburetor engine, during the intake stroke, the engine sucks in the finished fuel-air mixture, and its operation is practically no different from that of a conventional engine. The advantage of such a motor will be better efficiency.

Multi-point injection

Represents a further stage of improvement injection motors. Based on signals from the controller, fuel is supplied to each cylinder, but also to the intake manifold, i.e. The fuel assemblies are prepared outside the cylinder and enter the cylinder already ready.
In such an implementation of the principle of the injection engine, it is possible to provide many of the advantages inherent in the injection engine and noted earlier.

direct injection

Is the next stage of development injection engines. Fuel injection is carried out directly into the combustion chamber, which ensures the best efficiency of the internal combustion engine. The result of this approach is to obtain maximum power, minimum fuel consumption and best performance environmental safety.

Injection ICE is the next stage in the development of a gasoline engine, significantly improving its performance. In engines using a fuel injection system, power increases, as well as the economic efficiency of their work, they have a much lower negative impact on the environment.

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 the exhaust gases of vehicles. Until that time, the composition of combustion products of engines internal combustion no one was interested. 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 channels idle move carburetor with high speed sucking in too much fuel.

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

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

To reduce harmful emissions it was proposed to install an exhaust gas catalytic converter in the exhaust system. 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, taking into account the wear and contamination of the elements of the system and the internal combustion engine itself during its service life. The question arose about a system that could correct itself in the process of work, flexibly shifting the conditions for preparing the working mixture depending on external conditions.

The way out was found next. Feedback was introduced into the injection system - in the exhaust system, directly in front of the catalyst, they put an oxygen content sensor in the exhaust gases, the so-called lambda probe. This system was developed already taking into account the presence of such 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, 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 by improving the filling of cylinders, optimal installation 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.

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

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

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

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

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

Of all the above, perhaps not everyone knows what an adsorber is. The adsorber is an element of a closed circuit for the recirculation of gasoline vapors. Euro-2 standards prohibit the contact of the ventilation of the gas tank with the atmosphere, gasoline vapors must be collected (adsorbed) and sent to the cylinders for afterburning when purged. 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.

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 they are easily adapted for mono-injection carbureted engines almost without constructive alterations or technological changes in production. Single-point injection has an advantage over a carburetor in terms of fuel economy, environmental friendliness and relative stability and reliability of parameters. But in the throttle response of the engine, single-point injection loses. Another disadvantage: when using a single-point injection, as well as when using a carburetor, up to 30% of gasoline settles on the walls of the manifold.

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

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

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

As another and effective tool in optimizing the combustion of the mixture and increasing the efficiency of a gasoline engine, it implements simple
principles. Namely: it sprays fuel more thoroughly, mixes it better with air and more competently disposes of the finished mixture on different modes engine operation. As a result, direct injection engines consume less fuel than conventional "injection" engines (especially when quiet ride on not high 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 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, 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 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 to injection pump diesel 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 the air-fuel mixture to the candle and improving the filling of the cylinders with air (in a conventional engine, the vortex in the cylinder is twisted in the opposite direction).

GDI engine operating modes

In total, there are three modes of engine operation:

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

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

The operation of the engine on a very lean mixture set new problem- neutralization of 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.

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

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

Power mode(injection on the intake stroke). The so-called "homogeneous mixture mode" is used for intensive urban driving, high-speed suburban traffic and overtaking. Fuel is injected on the intake stroke with a conical torch, mixing with air and forming a homogeneous mixture, as in conventional engine with distributed injection. 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. Not a large number 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 is not intake tract, but directly into 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 the fuel system, the location of the nozzles and their design.

"Born" in 1951, the injector gradually replaced the carburetors, we read the article -. And this happened due to one of its most important advantages, which is to reduce the amount of fuel used. In addition to which experts also note better dynamics acceleration of injection cars, the stability of the operation of such engines, as well as the reduction in the number of harmful emissions from their work into the atmosphere.

Let's find out where such properties come from, and in general what is the principle of operation of the injector, but first I will briefly give the main disadvantages of the latter, so that you do not consider it ideal:

• expensive repair of nodes;
• the presence of elements that cannot be repaired;
• the need to use high-quality fuel;
• the need to use special equipment for diagnostics, repair and maintenance.

How does an injector work?

So, as you know, in modern cars carburetor system already completely replaced. The latter, unlike carburetor ones, increase the power of the car, improve the dynamics of its acceleration, and environmental friendliness. While fuel consumption is reduced.

By the way, the injector retains high environmental performance without various adjustments and settings. After all, there is a self-tuning of the air-fuel mixture, which became possible thanks to the oxygen sensor installed on the exhaust manifold (lambda probe).

Injector device.

Fuel is supplied to the injection engine by injectors, which can be located either on the intake manifold (single injection), or not far from intake valves cylinders ( distributed injection), or directly in the cylinder head - the cylinder head (direct injection - fuel is injected into the combustion chamber itself), we look at how to flush the nozzles with our own hands.

In addition to injectors, the injector includes the following actuators:

• ECU (controller) - processes data from sensors and controls fuel supply and ignition systems;
• gasoline pump (electric) - it supplies fuel;
• various sensors: temperature, crankshaft, camshaft, detonation;
• - maintains the difference in air pressure in the intake manifold and injectors.

Also, all injection engines are equipped with a catalytic converter (catalyst) in the form of "honeycombs", on which an active layer is applied, which contributes to the burning of the fuel remaining in the exhaust gases. However, refueling with leaded gasoline for a long time leads to certain breakdowns, due to which the catalyst loses its ability.

Oxygen sensor in the injector and its operation.

Most known type is a zirconium oxygen sensor, more details in the article -. It is a switch (by the way, one of the most important), which abruptly changes its state at around 0.5% of the oxygen contained in the exhaust gases.

The sensor interface device looks like this: a warm sensor (300 degrees Celsius and above) at a rich mixture (oxygen content< 0.5%), как слабый источник тока, устанавливает на выходе напряжение от 0,45 до 0,8 Вольт, а при бедной смеси (содержание кислорода >0.5%) - from 0.2 to 0.45 Volts. And it doesn’t matter what exactly the voltage level is, only where it is located in relation to the midline is taken into account. That is, fuel is added when the ECU detects a lean signal and reduced when it is rich. Consequently, the fuel supply is adjusted depending on the practical results of combustion, which allows the system to adapt to different conditions work.

It is known that this sensor works reliably only in a well-heated state, therefore, the TCCS ECU system will notice its readings only if the engine warms up to the desired level. However, this does not suit everyone. Therefore, to speed up this process, an electric heater is often mounted in the oxygen sensor.

TCCS computer. Self-diagnosis of the injector.

IN modern injector many sensors are installed, this allows you to optimize its operation.

The principle of operation of a mechanical injector.

Although other designs of injection engines with injection were previously used. For example, such an engine is known in which control is carried out using mechanical devices. The control here is the dosage of the volume of fuel using a special valve. The valve is controlled by a lever system, which is actuated by the air flow. Today, mechanically controlled valves have completely outlived their usefulness.

At present, each injection system has a built-in self-diagnosis subsystem, which allows you to establish malfunctions of nodes, sensors and executive mechanisms systems. After self-diagnosis, the computer generates diagnostic codes. They are retrieved from the computer memory and decrypted according to the tables. Each manufacturer has its own way of extracting these codes. You can find almost all of them freely available on the Internet, you can read more about do-it-yourself injector diagnostics. In addition, I recommend that you read the instructions about.

All modern cars with gasoline engines use an injection fuel supply system, since it is more advanced than a carburetor, despite the fact that it is structurally more complex.

The injection engine is not new, but it became widespread only after the development electronic technology. This is because it was very difficult to mechanically organize the control of a system with high accuracy. But with the advent of microprocessors, this became quite possible.

injection system differs in that gasoline is supplied in strictly specified portions forcibly into the manifold (cylinder).

The main advantage that the injection power system has is the observance of optimal proportions constituent elements combustible mixture in different operating modes power plant. This results in better power output and economical petrol consumption.

System device

The fuel injection system consists of electronic and mechanical components. The first controls the parameters of work power unit and on their basis gives signals for actuation of the executive (mechanical) part.

The electronic component includes a microcontroller (electronic control unit) and a large number of tracking sensors:

• crankshaft position;
• mass air flow;
• throttle position;
• detonation;
• coolant temperature;
• air pressure in the intake manifold.

Injector system sensors

Some cars may have a few more additional sensors. All of them have one task - to determine the parameters of the power unit and transfer them to the computer

As for the mechanical part, it includes the following elements:

• electric fuel pump;
• fuel lines;
• filter;
• pressure regulator;
• fuel rail;
• nozzles.

Simple fuel injection system

How it all works

Now consider the principle of operation of the injection engine separately for each component. With the electronic part, in general, everything is simple. Sensors collect information about the speed of rotation of the crankshaft, air (entered the cylinders, as well as its residual part in the exhaust gases), throttle position (associated with the accelerator pedal), coolant temperature. These data are constantly transmitted by the sensors to the electronic unit, due to which a high accuracy of gasoline dosing is achieved.

The ECU compares the information coming from the sensors with the data entered in the cards, and already on the basis of this comparison and a number of calculations, it controls the executive part. The so-called cards with optimal parameters the operation of the power plant (for example, for such conditions it is necessary to apply so much gasoline, for others - so much).

First injection Toyota engine 1973

To make it clearer, let's consider in more detail the algorithm of the electronic unit, but according to a simplified scheme, since in reality a very large amount of data is used in the calculation. In general, all this is aimed at calculating the temporal length of the electrical pulse that is applied to the injectors.

Since the circuit is simplified, we assume that the electronic unit only calculates according to several parameters, namely the base time pulse length and two coefficients - the coolant temperature and the oxygen level in the exhaust gases. To obtain the result, the ECU uses a formula in which all available data are multiplied.

To obtain the basic pulse length, the microcontroller takes two parameters - the speed of rotation of the crankshaft and the load, which can be calculated from the pressure in the manifold.

For example, the engine speed is 3000, and the load is 4. The microcontroller takes this data and compares it with the table entered on the map. IN this case we obtain a base time pulse length of 12 milliseconds.

But for calculations, it is also necessary to take into account the coefficients, for which readings are taken from the coolant temperature sensors and the lambda probe. For example, the temperature is 100 degrees, and the oxygen level in the exhaust gases is 3. The ECU takes this data and compares it with several more tables. Assume that the temperature coefficient is 0.8 and the oxygen coefficient is 1.0.

Having received all the necessary data, the electronic unit performs the calculation. In our case, 12 is multiplied by 0.8 and by 1.0. As a result, we get that the impulse should be 9.6 milliseconds.

The described algorithm is very simplified, but in fact, more than a dozen parameters and indicators can be taken into account in the calculations.

Since the data is constantly sent to the electronic unit, the system almost instantly responds to changes in the engine operating parameters and adjusts to them, ensuring optimal mixture formation.

It is worth noting that the electronic unit controls not only the fuel supply, its task also includes adjusting the ignition angle to ensure optimal engine operation.

Now about the mechanical part. Everything is very simple here: a pump installed in the tank pumps gasoline into the system, and under pressure to ensure forced supply. The pressure must be certain, so a regulator is included in the circuit.

On the highways, gasoline is supplied to the ramp, which connects all the nozzles. An electrical impulse supplied from the computer leads to the opening of the nozzles, and since gasoline is under pressure, it is simply injected through the opened channel.

Types and types of injectors

There are two types of injectors:

1. With single injection. Such a system is obsolete and is no longer used on cars. Its essence is that there is only one nozzle installed in the intake manifold. This design did not provide an even distribution of fuel over the cylinders, so its operation was similar to a carburetor system.
2. Multi-point injection. On modern cars, this type is used. Here, each cylinder has its own nozzle, so this system is characterized by high dosing accuracy. Nozzles can be installed both in the intake manifold and in the cylinder itself ( injector).

On a multi-point fuel injection system, several types of injection can be used:

1. Simultaneous. In this type, the impulse from the ECU goes to all the injectors at once, and they open together. Now such an injection is not used.
2. Paired, he is pairwise-parallel. In this type, the nozzles work in pairs. It is interesting that only one of them supplies fuel directly in the intake stroke, while the second cycle does not match. But since the engine is 4-stroke, with valve system gas distribution, then the mismatch of the injection on the cycle does not affect the performance of the motor.
3. Phased. In this type, the ECU sends open signals for each injector separately, so the injection occurs with the same stroke.

It is noteworthy that a modern fuel injection system can use several types of injection. So, in normal mode, phased injection is used, but in the event of a transition to emergency operation (for example, one of the sensors failed), the injection engine switches to paired injection.

Sensor Feedback

One of the main sensors, on the basis of which the ECU regulates the opening time of the injectors, is a lambda probe installed in the exhaust system. This sensor determines the residual (not burned) amount of air in the gases.

The evolution of the lambda probe from Bosch

Thanks to this sensor, the so-called " Feedback". Its essence is this: the ECU did all the calculations and gave an impulse to the injectors. Fuel entered, mixed with air and burned. The resulting exhaust gases with unburned particles of the mixture are removed from the cylinders through the exhaust gas removal system, in which the lambda probe is installed. Based on his readings, the ECU determines whether all calculations were carried out correctly and, if necessary, makes adjustments to obtain the optimal composition. That is, on the basis of the already completed stage of fuel supply and combustion, the microcontroller makes calculations for the next one.

It should be noted that during the operation of the power plant there are certain modes in which the readings oxygen sensor will be incorrect, which may disrupt the operation of the motor or a mixture with a certain composition is required. In such modes, the ECU ignores information from the lambda probe, and it sends signals for the supply of gasoline based on the information stored in the maps.

In different modes, the feedback works like this:

• Starting the motor. In order for the engine to be able to start, an enriched combustible mixture with an increased percentage of fuel is needed. And the electronic unit provides this, and for this it uses the given data, and it does not use information from the oxygen sensor;
• Warming up To make the injection engine gain faster operating temperature The ECU sets the engine speed to high. At the same time, he constantly monitors its temperature, and as it warms up, it adjusts the composition of the combustible mixture, gradually depleting it until its composition becomes optimal. In this mode, the electronic unit continues to use the data specified in the cards, still not using the readings of the lambda probe;
• Idling. In this mode, the engine is already fully warmed up, and the exhaust gas temperature is high, so the conditions for correct operation lambda probes are respected. The ECU is already starting to use the readings of the oxygen sensor, which allows you to set the stoichiometric composition of the mixture. With this composition, the greatest power output of the power plant is provided;
• Movement with a smooth change in engine speed. For achievement economical consumption fuel at maximum power output, a mixture with a stoichiometric composition is needed, therefore, in this mode, the ECU regulates the supply of gasoline based on the readings of the lambda probe;
• A sharp increase in turnover. In order for the injection engine to respond normally to such an action, a slightly enriched mixture is needed. To provide it, the ECU uses card data, and not lambda probe readings;
• Motor braking. Since this mode does not require power output from the motor, it is enough that the mixture simply does not allow the power plant to stop, and a lean mixture is also suitable for this. For its manifestation, the readings of the lambda probe are not needed, so the ECU does not use them.

As you can see, although the lambda probe is very important for the operation of the system, the information from it is not always used.

Finally, we note that although the injector is a structurally complex system and includes many elements, the breakdown of which immediately affects the operation of the power plant, but it provides a more rational consumption of gasoline, and also increases the environmental friendliness of the car. Therefore, there is no alternative to this power system yet.

Autoleek

Injection engine - what do we know about it? It is they who are equipped with any modern car. The implementation of the resource of such an internal combustion engine (ICE) is designed for economical fuel consumption, minimizing its exhaust into the environment. Let's spend small digression to study the unit.

What does he work for?

They work in cycles; each cycle provides an operation:

1. Filling fuel cylinders.
2. Compressing it with a piston for combustion.
3. Working stroke - obtaining mechanical energy by detonating a combustible substance.
4. The output of processed raw materials into the atmosphere.

The most demanded by the auto industry are 4-x gasoline-powered. On their example, we will study the principle of operation of the injection engine.

During the first stroke, the piston goes down as much as possible - gasoline mixed with air is supplied through the valve. Further, the piston rises to the stop, closing the valve and compressing the mixture. After that, the candle cuts off the spark - it starts the detonation of the compressed substance.

The increase in temperature in the chamber and the formation of gases move the piston forward, and the crankshaft returns it to the top position due to inertia. At high speeds, the pressure is built up even more, the outlet valve opens. Gasoline processing products rush to it.

For more rational functioning, a set of sensors is used that determine the load received on the mechanisms, calculate the portions of the components of the detonating mixture to ensure movement with a cycle equal to the clock cycle.

Their software “stuffing” is designed so that each one works in parallel with the motor modes, monitors changes in cycles and adjusts to them. This functionality allows you to adjust fuel consumption to your individual driving style and increase efficiency.

What are the features of the device?

Studying the design will allow you to understand in more detail how the injection engine works. Components specific to this type:

• Block electronic control(ECU);
• Pressure regulator;
• nozzles;
• Gasoline pump;
• Sensors.

The interaction of the above: sensors receive data on the state of mechanics or processes, they are processed by the processor and transmit control commands. The nozzles are given a limited charge, which opens them. The result is that the mixture from the fuel section enters the intake manifold compartment.

To make this process more understandable, let us brief digression on the arrangement of some of the components that make up the engine injector.

ECU

Its main function is to continuously issue commands to the components of the car based on the processed information. It includes:

• environmental factors (temperature, humidity, etc.);
• the degree of load on the mechanics (when climbing a hill, moving along bad road, etc.);
• motor mode (idling / high-speed running, taking into account the load when switching to four-wheel drive, etc.).

In case of discrepancies in the original program, the computer sets adjustments to the executing elements. The unit is capable of diagnostics. The driver is notified about the failure of any executor mechanism, its incorrect functioning by indicating the CheckEngine on dashboard. Information about errors is collected in the memory department, which, in case of serious breakdowns, helps to promptly detect and eliminate them.

Types of embedded memory devices:

• One Time Programmable Read Only Memory (PROM) - contains the basic programming code("brain" of the car). Its chip is located on the panel board; in case of failure, it is easily replaced with a new one. In case of any failures, nested codes remain stored on it.
• Random access memory (RAM) is a temporary reservoir used to process tasks for the current session. The device is soldered to the board; when the power supply from the battery is cut off, all information from it is erased.
• Electrically programmable (EEPROM) - contains temporary data and anti-theft coding. It uses a built-in battery that is recharged while driving. Through it, the sewn-in electronic lock codes and the same immobilizer parameters are compared. If they do not match, the injection engine cannot be started.

nozzles

Through them, portions of the fuel mass are splashed into the manifold and cylinder compartments, and the opening / closing of the valve is repeated many times within a second.

According to the method of hardware control and the number of parts used, they are divided into categories:

1. Throttle Mono Injection (TBI) - the supply of raw materials for detonation is carried out in one piece. The supply jet is not synchronized with the actuation of the inlet valve. The control signals for the injector message are produced from an intra-manifold chip. The principle is common on old motors of the 90s.
2. Distribution injection (MFI) - used in all modern cars with on-board computer. The transfer of fuel is complete: one nozzle - one cylinder. The nozzle block is mounted on top of the manifold, and the whole process is synchronized with the CBU, according to how the injection engine ignition system works. When comparing the summary characteristics of predecessors - the efficiency increased to 10%.

MFI-elements for jet supply are: electro-hydraulic, electromagnetic, piezoelectric. They are used in the distribution of injection:

• Simultaneous (synchronous filling of all cylinders);
• Pairwise-parallel - one pair of pistons takes the lower position, the other - the upper one. The filling of fuel and the removal of combustion products are carried out in the same way;
• Two-stage (phase) - the transfer of fuel to the combustion chambers is carried out in two operations.
• Directly - it is used in motor designs that involve the combustion of an oxygen-depleted composition.

An important fact: TBI technology is practically not common today, as it is less economical and unreliable!

catalytic converter

This device makes it possible to reduce the content of substances such as carbon and nitrogen oxides in the exhaust gases by converting them into hydrocarbons. Not controlled by the ECU, but interacts with the processing center through a sensor that determines the percentage of oxygen in the exhaust accumulations. In case of excessive fuel supply, the controller receives information from the sensor and corrects it.

The converter contains ceramic elements with built-in catalysts:

• oxidizing (platinum and palladium);
• restorative rhodium;
• selective;
• cumulative.

Note: leaded gasoline is detrimental to the operation of converters, and filling substances with high content sulfur will render the elements of accumulative catalysis unusable!

Sensors

The well-coordinated work of all mechanisms of injection engines is ensured by the readings of mini-devices fixed on aggregate performers. Each device measures the parameters of the controlled area and transmits them to the computer.

Built-in sensors ® :

1. DMRV (R mass air flow) - mounted at the inlet to air filter. Operates on the principle of comparison of indications. Current flows through 2 platinum filaments. Resistance changes (depends on temperature). In this case, one thread is freely blown, the second is hermetically sealed. Due to the difference that has appeared, the ECU makes a calculation.
2. DBP (R absolute pressure and temperature in the engine) - combined or set separately from the previous one. It consists of 2 chambers: one is sealed (vacuum inside), the second is supplied directly to the manifold intake chamber. A diaphragm passes between the chambers, piezoelectric elements are fixed, which create tension when it moves.
3. DPKV (R crankshaft position) - is installed in the form of a magnetic comb on the crankshaft pulley. It is equipped with 58 teeth and 2 gaps equal to the tooth pitch. The teeth move in a copper winding, which, when interacting with a magnetized core, forms an inductive voltage - it depends on the speed of the pulley.
4. DF (R phase) - contains a disk with a coil and a slot. The slot addresses the instrument - output voltage equalizes with zero. At the same time, compression top dead center is reached in the first cylinder. Due to this, the central unit outputs voltage to desired cylinder for ignition, controls the cycles.
5. DD (R detonation) - they are equipped with a cylinder block. At the moment of detonation, vibration passes through it. The transmission of information is based on the generation of free current voltage - it increases with greater vibration.
6. TPS (R throttle position) - when reference voltage at 5 V, it increases or decreases due to a change in the rotary angle of the damper.
7. DTOZH (R coolant temperature).
8. Oxygen sensor - for different designs, it is introduced singly or in pairs. Takes measurements of free oxygen in exhaust products. Its function allows the ECU to determine whether to enrich or lean the fuel mixture.

Injector significantly better carburetor. To verify this, consider a comparison of similar motor structures in the table: