Fuel injection systems for gasoline engines. Electronic fuel injection - how does it work? Design, principle of operation and types of fuel injection systems

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

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

This is what the fuel injection system looks like

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

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

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

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

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

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

How does an injector work?

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

Sensor mass flow air

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

Throttle position sensor

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

Oxygen sensor

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

Crankshaft position sensor

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

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

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

IN modern cars in gasoline power plants The principle of operation of the power system is similar to that used on diesel engines. In these engines it is divided into two - intake and injection. The first provides air supply, and the second - fuel. But due to design and operational features, the functioning of injection differs significantly from that used on diesel engines.

Note that the difference in the injection systems of diesel and gasoline engines is increasingly erased. To receive best qualities designers borrow design solutions and apply them to different types power systems.

Design and principle of operation of the injection injection system

The second name for injection systems in gasoline engines is injection. Its main feature is the precise dosage of fuel. This is achieved by using nozzles in the design. The engine injection device includes two components - executive and control.

The task of the executive part is to supply gasoline and spray it. It does not include many components:

1. Pump (electric).
2. Filter element (fine filter).
3. Fuel lines.
4. Ramp.
5. Injectors.

But these are only the main components. The executive component may include a number of additional components and parts - a pressure regulator, a system for draining excess gasoline, an adsorber.

The task of these elements is to prepare the fuel and ensure its flow to the injectors, which are used to inject them.

The operating principle of the executive component is simple. When you turn the ignition key (on some models - when you open the driver's door), the electric pump turns on, which pumps gasoline and fills the remaining elements with it. The fuel is cleaned and flows through fuel lines into a ramp that connects the injectors. Due to the pump, the fuel in the entire system is under pressure. But its value is lower than on diesel engines.

The opening of the injectors is carried out due to electrical impulses supplied from the control part. This component of the fuel injection system consists of a control unit and a whole set of tracking devices - sensors.

These sensors monitor indicators and operating parameters - crankshaft rotation speed, amount of air supplied, coolant temperature, throttle position. The readings are sent to the control unit (ECU). He compares this information with the data stored in memory, on the basis of which the length of the electrical pulses supplied to the injectors is determined.

The electronics used in the control part of the fuel injection system are needed to calculate the time for which the injector should open in a particular operating mode of the power unit.

Types of injectors

But note that this is the general design of the supply system of a gasoline engine. But several injectors have been developed, and each of them has its own design and operating features.

Engine injection systems are used on cars:

• central;
• distributed;
• direct.

Central injection is considered the first injector. Its peculiarity is the use of only one injector, which injected gasoline into the intake manifold simultaneously for all cylinders. Initially, it was mechanical and no electronics were used in the design. If we consider the design of a mechanical injector, it is similar to carburetor system, with the only difference that instead of a carburetor, a mechanically driven injector was used. Over time, the central feed was made electronic.

Now this type is not used due to a number of disadvantages, the main of which is the uneven distribution of fuel among the cylinders.

Distributed injection is currently the most common system. The design of this type of injector is described above. Its peculiarity is that each cylinder has its own fuel injector.

In this type of design, the injectors are installed in the intake manifold and located next to the cylinder head. The distribution of fuel among the cylinders makes it possible to ensure an accurate dosage of gasoline.

Direct injection is now the most advanced type of gasoline supply. In the previous two types, gasoline was supplied to the passing air stream, and mixture formation began to take place in the intake manifold. The design of the same injector copies the diesel injection system.

In a direct feed injector, the nozzle nozzles are located in the combustion chamber. As a result, the components of the air-fuel mixture are launched into the cylinders separately, and they are mixed in the chamber itself.

The peculiarity of this injector is that high fuel pressure is required to inject gasoline. And its creation is ensured by one more unit added to the device of the executive part - a high-pressure pump.

Diesel engine power systems

And diesel systems are being modernized. If earlier it was mechanical, now diesel engines are also equipped electronically controlled. It uses the same sensors and control unit as a gasoline engine.

There are currently three types of diesel injections used on cars:

1. With distribution injection pump.
2. Common Rail.
3. Pump injectors.

As in gasoline engines, the diesel injection design consists of an executive and control parts.

Many elements of the executive part are the same as those of the injectors - tank, fuel lines, filter elements. But there are also components that are not found on gasoline engines - a fuel priming pump, injection pump, lines for transporting fuel under high pressure.

In the mechanical systems of diesel engines, in-line injection pumps were used, in which the fuel pressure for each injector was created by its own separate plunger pair. Such pumps were highly reliable, but were bulky. The injection timing and the amount of injected diesel fuel were regulated by a pump.

In engines equipped with a distribution injection pump, the pump design uses only one plunger pair, which pumps fuel to the injectors. This unit is compact in size, but its service life is lower than that of in-line units. This system is used only on passenger vehicles.

Common Rail is considered one of the most efficient diesel engine injection systems. Its general concept is largely borrowed from a separate feed injector.

In such a diesel engine, the moment of start of supply and the amount of fuel is “managed” by the electronic component. The task of the high pressure pump is only to pump diesel fuel and create high pressure. Moreover, diesel fuel is not supplied directly to the injectors, but into a ramp connecting the injectors.

Pump injectors are another type of diesel injection. In this design, there is no fuel injection pump, and the plunger pairs that create diesel fuel pressure are included in the injector device. This design solution allows you to create the most high values fuel pressure among existing types of injection on diesel units.

Finally, we note that information on types of engine injection is provided here in general. To understand the design and features of these types, they are considered separately.

Video: Fuel injection system control

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

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

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

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

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

The injection system remains key integral part general fuel system of any car. The central working element of such a system is the fuel nozzle (injector).

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

Types of injection systems on gasoline internal combustion engines

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

Central injection

The fuel supply in the central injection system occurs through a fuel injector, which is located in the intake manifold. Since there is only one nozzle, this injection system is also called mono-injection.

Systems of this type have lost their relevance today, so they are not provided in new car models, however, in some older models of some car brands you can meet them.

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

Distributed injection

The multipoint injection system supplies fuel separately to each cylinder, equipped with its own fuel injector. In this case, fuel assemblies are formed only in the intake manifold.

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

Direct injection

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

The direct fuel supply system allows obtaining a high-quality fuel assembly composition at all stages internal combustion engine operation in order to improve the combustion process of the combustible mixture, increase the operating power of the engine, and reduce the level of exhaust gases.

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

Combined injection

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

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

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

Types of injection systems for diesel internal combustion engines

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

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

The injection pump is the central element of any fuel system diesel engine.

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

Today, preference is given to the system direct injection, which is characterized by an increased noise level and less smooth operation engine, compared to injection into the preliminary chamber, but it provides a much more important indicator - efficiency.

Pump-injector injection system

A similar system is used to supply and inject a fuel mixture under high pressure. central device- pump injectors.

You can guess from the name that the key feature of this system is that two functions are combined in a single device (pump injector): creating pressure and injection.

A design disadvantage of this system is that the pump is equipped with a permanent drive from the engine camshaft (cannot be switched off), which leads to rapid wear of the structure. Because of this, manufacturers are increasingly choosing the Common Rail injection system.

Common Rail injection system (battery injection)

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

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

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

To control injection systems on diesel engines, mechanical and electronic devices. Mechanical systems allow you to control operating pressure, volume and timing of fuel injection. Electronic systems provide for more efficient control of diesel internal combustion engines in general.

Direct injection (also called direct injection, or GDI) has started appearing on cars more recently. However, the technology is gaining popularity and is increasingly found on the engines of new cars. Today we are in general outline Let's try to answer what direct injection technology is and should we be afraid of it?

To begin with, it is worth noting that the main distinctive feature technology is the location of the injectors, which are placed directly in the cylinder head, respectively, and injection under enormous pressure occurs directly into the cylinders, in contrast to the long-proven the best side fuel into the intake manifold.

Direct injection was first tested in mass production by the Japanese automaker Mitsubishi. Operation showed that among the advantages, the main advantages were efficiency - from 10% to 20%, power - plus 5% and environmental friendliness. The main disadvantage is that injectors are extremely demanding on fuel quality.

It is also worth noting that a similar system has been successfully installed on for many decades. However, it was on gasoline engines that the use of technology was associated with a number of difficulties that have not yet been completely resolved.

A video from the Savagegeese YouTube channel explains what direct injection is and what can go wrong when operating a car with this system. In addition to the main pros and cons, the video also explains the ins and outs of preventative system maintenance. In addition, the video touches on the topic of injection systems into the intake channels, which can be seen in abundance on older engines, as well as those that use both methods of fuel injection. Using Bosch diagrams clearly, the presenter explains how it all works.

To find out all the nuances, we suggest watching the video below (turning on the subtitle translation will help you figure it out if you don’t know English very well). For those who are not too interested in watching, you can read about the main pros and cons of direct gasoline injection below, after the video:

So, environmental friendliness and efficiency are good goals, but here are the risks of using modern technology in your car:

Cons

1. Very complex design.

2. This leads to the second important issue. Since young gasoline technology involves major changes to the design of engine cylinder heads, the design of the injectors themselves, and associated changes to other engine parts, for example, the injection pump (high pressure fuel pump), the cost of cars with direct fuel injection is higher.

3. The production of the power system parts themselves must also be extremely precise. The nozzles develop pressure from 50 to 200 atmospheres.

Add to this the operation of the injector in close proximity to the combustible fuel and the pressure inside the cylinder and you get the need to produce very high-strength components.

4. Since the injector nozzles look into the combustion chamber, all gasoline combustion products are also deposited on them, gradually clogging or disabling the injector. This is perhaps the most serious disadvantage of using the GDI design in Russian realities.

5. In addition, it is necessary to carefully monitor the condition of the engine. If oil loss begins to occur in the cylinders, the products of its thermal decomposition will quickly disable the injector and clog intake valves, forming an indelible coating of sediment on them. Do not forget that classic injection with nozzles located in the intake manifold cleans the intake valves well, washing them with fuel under pressure.

6. Expensive repairs and the need for preventative maintenance, which is also not cheap.

In addition, it also explains that if not used properly, direct injection vehicles can experience valve contamination and poor performance, especially on turbocharged engines.

Modern cars use various fuel injection systems. The injection system (another name is the injection system, from injection) as the name suggests, provides fuel injection.

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

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

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

Gasoline engine injection systems

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

Diesel injection systems

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

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

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

On cars With diesel engine Various designs of injection systems are installed: with in-line injection pump, with distribution injection pump, pump injectors, Common Rail. Progressive injection systems - pump injectors and Common Rail system.