Fuel injection systems for engines
Auto Terms,  Car device

Engine fuel injection systems

The work of any internal combustion engine is based on the combustion of gasoline, diesel fuel or other type of fuel. Moreover, it is important that the fuel mixes well with air. Only in this case, the maximum output will be from the motor.

Carburetor motors do not have the same performance as modern injection engines. Often, a unit equipped with a carburetor has less power than an internal combustion engine with a forced injection system, despite the larger volume. The reason lies in the quality of the mixing of gasoline and air. If these substances mix poorly, part of the fuel will be removed to the exhaust system, where it will burn out.

In addition to the failure of some elements of the exhaust system, for example, a catalyst or valves, the engine will not use its full potential. For these reasons, a forced fuel injection system is installed on a modern engine. Let's consider its various modifications and their principle of operation.

What is fuel injection system

The gasoline injection system means the mechanism for the forced metered flow of fuel into the engine cylinders. Considering that with poor combustion of BTC, the exhaust contains many harmful substances that pollute the environment, engines in which precise injection is performed are more environmentally friendly.

Fuel injection systems for engines

To improve mixing efficiency, the process control is electronic. Electronics more efficiently doses a portion of gasoline, and also allows you to distribute it into small parts. A little later we will discuss different modifications of injection systems, but they have the same principle of operation.

Principle of operation and device

If earlier forced fuel supply was carried out only in diesel units, then a modern gasoline engine is also equipped with a similar system. Its device, depending on the type, will include the following elements:

  • The control unit that processes the signals received from the sensors. Based on these data, he gives a command to the actuators about the time of petrol spraying, the amount of fuel and the amount of air.Fuel injection systems for engines
  • Sensors installed near the throttle valve, around the catalyst, on the crankshaft, camshaft, etc. They determine the amount and temperature of the incoming air, its amount in the exhaust gases, and also record different parameters of the power unit operation. The signals from these elements help the control unit to regulate fuel injection and air supply to the desired cylinder.
  • The injectors spray gasoline either into the intake manifold or directly into the cylinder chamber, as in a diesel engine. These parts are located in the cylinder head near the spark plugs or on the intake manifold.Fuel injection systems for engines
  • A high-pressure fuel pump that creates the necessary pressure in the fuel line. In some modifications of fuel systems, this parameter should be much higher than the cylinder compression.

The system operates on a principle similar to the carburetor analog - at the moment when the air flow enters the intake manifold, the nozzle (in most cases, their number is identical to the number of cylinders in the block). The first developments were of a mechanical type. Instead of a carburetor, one nozzle was installed in them, which sprayed gasoline into the intake manifold, due to which the portion was burned more efficiently.

It was the only element that worked from electronics. All other actuators were mechanical. More modern systems operate on a similar principle, only they differ from the original analogue in the number of actuators and the place of their installation.

Various types of systems provide a more homogeneous mixture, so that the vehicle uses the full potential of the fuel, and also meets more stringent environmental requirements. A pleasant bonus to the work of electronic injection is the efficiency of the vehicle with the effective power of the unit.

Fuel injection systems for engines

If in the first developments there was only one electronic element, and all other parts of the fuel system were of a mechanical type, then modern engines are equipped with completely electronic devices. This allows you to more accurately distribute less gasoline with more efficiency from its combustion.

Many motorists know this term as an atmospheric engine. In this modification, the fuel enters the intake manifold and cylinders due to the vacuum generated when the piston approaches dead-bottom on the intake stroke. All carburetor ICEs work according to this principle. Most modern injection systems work on a similar principle, only atomization is carried out due to the pressure that the fuel pump creates.

Brief history of appearance

Initially, all gasoline engines were equipped exclusively with carburetors, because for a long time this was the only mechanism by which fuel was mixed with air and sucked into the cylinders. The operation of this device is that a small portion of gasoline is sucked into the air stream passing through the chamber of the mechanism into the intake manifold.

For over 100 years, the device has been refined, so that some models are able to adapt to different modes of motor operation. Of course, electronics do this job much better, but at that time it was the only mechanism, the refinement of which made it possible to make the car either economical or fast. Some sports car models were even equipped with separate carburetors, which significantly increased the power of the car.

Fuel injection systems for engines

In the mid-90s of the last century, this development was gradually replaced by a more efficient type of fuel systems, which no longer worked due to the parameters of the nozzles (about what it is and how their size affects the operation of the engine, read in separate article) and the volume of the carburetor chambers, and based on signals from the ECU.

There are several reasons for this replacement:

  1. The carburetor type of systems is less economical than the electronic analogue, which means that it has low fuel efficiency;
  2. The effectiveness of the carburetor is not manifested in all modes of engine operation. This is due to the physical parameters of its parts, which can only be changed by installing other suitable elements. In the process of changing the operating modes of the internal combustion engine, while the car continues to move, this cannot be done;
  3. Carburetor performance depends on where it is installed on the engine;
  4. Since the fuel in the carburetor mixes less well than when sprayed with an injector, more unburned gasoline enters the exhaust system, which increases the level of environmental pollution.

The fuel injection system was first used on production vehicles in the early 80s of the twentieth century. However, in aviation, injectors began to be installed 50 years earlier. The first car that was equipped with a mechanical direct injection system from the German company Bosch was the Goliath 700 Sport (1951).

Fuel injection systems for engines

The well-known model called "Gull Wing" (Mercedes-Benz 300SL) was equipped with a similar modification of the vehicle.

Fuel injection systems for engines

In the late 50s - early 60s. systems were developed that would operate from a microprocessor, and not due to complex mechanical devices. However, these developments remained inaccessible for a long time, until it became possible to purchase cheap microprocessors.

The massive introduction of electronic systems was driven by stricter environmental regulations and greater availability of microprocessors. The first production model to receive electronic injection was the 1967 Nash Rambler Rebel. For comparison, the carbureted 5.4-liter engine developed 255 horsepower, while the new model with the electrojector system and the identical volume already had 290 hp.

Fuel injection systems for engines

Due to greater efficiency and increased efficiency, various modifications of injection systems have gradually replaced carburetors (although such devices are still actively used on small mechanized vehicles due to their low cost).

Most passenger cars today are equipped with electronic fuel injection from Bosch. The development is called jetronic. Depending on the modification of the system, its name will be supplemented with the corresponding prefixes: Mono, K / KE (mechanical / electronic metering system), L / LH (distributed injection with control for each cylinder), etc. A similar system was developed by another German company - Opel, and it is called Multec.

Types and types of fuel injection systems

All modern electronic forced injection systems fall into three main categories:

  • Over-throttle spray (or central injection);
  • Collector spray (or distributed);
  • Direct atomization (the atomizer is installed in the cylinder head, the fuel is mixed with air directly in the cylinder).

The scheme of operation of all these types of injections is almost identical. It supplies fuel to the cavity due to the excess pressure in the fuel system line. This can be either a separate reservoir located between the intake manifold and the pump, or the high pressure line itself.

Central injection (single injection)

Monoinjection was the very first development of electronic systems. It is identical to the carburetor counterpart. The only difference is that an injector is installed in the intake manifold instead of a mechanical device.

Gasoline goes directly to the manifold, where it mixes with the incoming air and enters the corresponding sleeve, in which a vacuum is created. This novelty significantly increased the efficiency of standard motors due to the fact that the system can be adjusted to the operating modes of the motor.

Fuel injection systems for engines

The main advantage of mono injection is the simplicity of the system. It can be installed on any engine instead of the carburetor. The electronic control unit will control just one injector, so no complicated microprocessor firmware is needed.

In such a system, the following elements will be present:

  • To maintain a constant pressure of gasoline in the line, it must be equipped with a pressure regulator (how it works and where it is installed is described here). When the engine is shut down, this element maintains the line pressure, making it easier for the pump to operate when the unit is restarted.
  • An atomizer that operates on signals from an ECU. The injector has a solenoid valve. It provides impulse atomization of gasoline. More details about the device of the injectors and how they can be cleaned are described here.
  • The motorized throttle valve regulates the air entering the manifold.
  • Sensors that collect information necessary to determine the amount of gasoline and when it is sprayed.
  • The microprocessor control unit processes the signals from the sensors, and, in accordance with this, sends a command to operate the injector, throttle drive and fuel pump.

While this innovative design has performed well, it has several critical disadvantages:

  1. When the nozzle fails, it completely stops the entire motor;
  2. Since spraying is done in the main part of the manifold, some gasoline remains on the pipe walls. Because of this, the engine will require more fuel to achieve peak power (although this parameter is noticeably lower compared to the carburetor);
  3. The disadvantages listed above stopped the further improvement of the system, which is why the multi-point spray mode is not available in single injection (it is possible only in direct injection), and this leads to incomplete combustion of a portion of gasoline. As a result, the vehicle does not meet the ever-growing environmental requirements of vehicles.

Distributed Injection

The next more efficient modification of the injection system provides for the use of individual injectors for a specific cylinder. Such a device made it possible to locate the atomizers closer to the inlet valves, due to which there is less fuel loss (not so much remains on the manifold walls).

Usually, this type of injection is equipped with an additional element - a rail (or a reservoir in which fuel is accumulated under high pressure). This design allows each injector to be provided with the proper gasoline pressure without complex regulators.

Fuel injection systems for engines

This type of injection is most often used in modern cars. The system has shown a fairly high efficiency, so today there are several of its varieties:

  • The first modification is very similar to the work of a mono injection. In such a system, the ECU sends a signal to all the injectors at the same time, and they are triggered regardless of which cylinder needs a fresh portion of BTC. The advantage over single injection is the ability to individually adjust the supply of gasoline to each cylinder. However, this modification has significantly higher fuel consumption than more modern counterparts.
  • Parallel pair injection. It works identically to the previous one, only not all injectors work, but they are connected in pairs. The peculiarity of this type of device is that they are paralleled so that one sprayer opens before the piston performs the intake stroke, and the other sprayed gasoline at that moment before starting the release from another cylinder. This system is almost never installed on cars, however, most electronic injections when switching to emergency mode work according to this principle. Often it is activated when the camshaft sensor fails (in a phased injection modification).
  • Phased modification of distributed injection. This is the most recent development of such systems. It has the best performance in this category. In this case, the same number of nozzles is used as there are cylinders in the engine, only spraying will be done just before opening the intake valves. This type of injection has the highest efficiency in this category. The fuel is not sprayed into the entire manifold, but only into the part from which the air-fuel mixture is taken. Thanks to this, the internal combustion engine demonstrates excellent efficiency.

Direct injection

The direct injection system is a kind of distributed type. The only difference in this case is the location of the nozzles. They are installed in the same way as spark plugs - at the top of the engine so that the sprayer supplies fuel directly to the cylinder chamber.

Cars of the premium segment are equipped with such a system, since it is the most expensive, but today it is the most efficient. These systems bring the mixing of fuel and air to almost ideal, and in the process of operation of the power unit, every micro-drop of gasoline is used.

Direct injection allows you to more accurately regulate the operation of the motor in different modes. Due to the design features (in addition to valves and candles, an injector must also be installed in the cylinder head), they are not used in small-displacement internal combustion engines, but only in powerful counterparts with a large volume.

Fuel injection systems for engines

Another reason for using such a system only in expensive cars is that the serial engine needs to be seriously modernized in order to install direct injection on it. If, in the case of other analogues, such an upgrade is possible (only the intake manifold needs to be modified and the necessary electronics installed), then in this case, in addition to installing the appropriate control unit and the necessary sensors, the cylinder head must also be redone. It is impossible to do this in budget serial power units.

The type of spraying in question is very whimsical to the quality of gasoline, because the plunger pair is very sensitive to the smallest abrasives and needs constant lubrication. It must meet the manufacturer's requirements, so cars with similar fuel systems should not be refueled at questionable or unfamiliar gas stations.

With the advent of more advanced modifications of the direct type of spray, there is a high probability that such engines will soon replace analogs with mono- and distributed injection. More modern types of systems include developments in which multipoint or stratified injection is performed. Both options are aimed at ensuring that the combustion of gasoline is as complete as possible, and the effect of this process reaches the highest efficiency.

Multi-point injection is provided by the sprayer feature. In this case, the chamber is filled with microscopic droplets of fuel in different parts, which improves uniform mixing with air. Layer-by-layer injection divides one portion of the BTC into two parts. The pre-injection is performed first. This part of the fuel ignites faster as there is more air. After ignition, the main part of the gasoline is supplied, which ignites no longer from a spark, but from an existing torch. This design makes the engine run more smoothly without loss of torque.

Fuel injection systems for engines

A mandatory mechanism that is present in all fuel systems of this type is a high pressure fuel pump. So that the device does not fail in the process of creating the required pressure, it is equipped with a plunger pair (what it is and how it works is described separately). The need for such a mechanism is due to the fact that the pressure in the rail must be several times higher than the compression of the engine, because often gasoline must be sprayed into the already compressed air.

Fuel injection sensors

In addition to the key elements of the fuel system (throttle, power supply, fuel pump and atomizers), its operation is inextricably linked to the presence of various sensors. Depending on the type of injection, these devices are installed for:

  • Determination of the amount of oxygen in the exhaust. For this, a lambda probe is used (how it works can be read here). Cars can use one or two oxygen sensors (installed either before or before and after the catalyst);Fuel injection systems for engines
  • Valve timing definitions (what is it, learn from another review) so that the control unit can send a signal to open the sprayer just before the intake stroke. The phase sensor is installed on the camshaft and is used in phased injection systems. A breakdown of this sensor switches the control unit to a pairwise-parallel injection mode;
  • Determination of the crankshaft speed. The operation of the ignition moment, as well as other auto systems, depends on the DPKV. This is the most important sensor in the car. If it fails, the motor cannot be started or it will stall;Fuel injection systems for engines
  • Calculating how much air is consumed by the engine. Mass air flow sensor helps the control unit determine by which algorithm to calculate the amount of gasoline (spray opening time). In the event of a breakdown of the mass air flow sensor, the ECU has an emergency mode, which is guided by the indicators of other sensors, for example, DPKV or emergency calibration algorithms (the manufacturer sets average parameters);
  • Determination of engine temperature conditions. The temperature sensor in the cooling system allows you to adjust the fuel supply, as well as the ignition timing (to avoid detonation due to engine overheating);
  • Calculate the estimated or real load on the powertrain. For this, a throttle sensor is used. It determines to what extent the driver presses the gas pedal;Fuel injection systems for engines
  • Preventing engine knocking. For this, a knock sensor is used. When this device detects sharp and premature shocks in the cylinders, the microprocessor adjusts the ignition timing;
  • Calculating the speed of the vehicle. When the microprocessor detects that the speed of the car exceeds the required engine speed, the "brains" turn off the fuel supply to the cylinders. This happens, for example, when the driver uses engine braking. This mode allows you to save fuel on descents or when approaching a turn;
  • Estimates of the amount of vibration affecting the motor. This happens when vehicles are driving on uneven roads. Vibrations can lead to misfire. These sensors are used in motors that comply with Euro 3 and higher standards.

No control unit operates solely on the basis of data from a single sensor. The more of these sensors in the system, the more efficiently the ECU will calculate the fuel characteristics of the engine.

Failure of some sensors puts the ECU into emergency mode (the motor icon lights up on the instrument panel), but the engine continues to operate according to pre-programmed algorithms. The control unit can be based on indicators of the operating time of the internal combustion engine, its temperature, the position of the crankshaft, etc., or simply according to a programmed table with different variables.

Executive mechanisms

When the electronic control unit has received data from all sensors (their number is stitched into the program code of the device), it sends the appropriate command to the actuators of the system. Depending on the modification of the system, these devices can have their own design.

These mechanisms include:

  • Sprayers (or nozzles). They are mainly equipped with a solenoid valve that is controlled by an ECU algorithm;
  • Fuel pump. Some car models have two of them. One supplies fuel from the tank to the high pressure fuel pump, which pumps gasoline into the rail in small portions. This creates sufficient pressure in the high-pressure line. Such modifications of the pumps are needed only in direct injection systems, since in some models the nozzle must spray the fuel in the compressed air;Fuel injection systems for engines
  • The electronic module of the ignition system - receives a signal for the formation of a spark at the right moment. This element in the latest modifications of on-board systems is part of the control unit (its low-voltage part, and the high-voltage part is a dual-circuit ignition coil, which creates a charge for a specific spark plug, and in more expensive versions, an individual coil is installed on each spark plug).
  • Idle speed regulator. It is presented in the form of a stepper motor that regulates the amount of air passage in the area of ​​the throttle valve. This mechanism is necessary to maintain idle engine speed when the throttle is closed (the driver does not press the gas pedal). This facilitates the process of warming up the cooled engine - you do not need to sit in a cold cabin in winter and gas up so that the engine does not stall;
  • To adjust the temperature regime (this parameter also affects the supply of gasoline to the cylinders), the control unit periodically activates the cooling fan installed near the main radiator. The latest generation of BMW models are equipped with a radiator grille with adjustable fins to maintain temperature during driving in cold weather and accelerate engine warm-up.Fuel injection systems for engines (so that the internal combustion engine does not overcool, the vertical ribs rotate, blocking the access of the cold air flow to the engine compartment). These elements are also controlled by the microprocessor based on data from the coolant temperature sensor.

The electronic control unit also records how much fuel the vehicle has consumed. This information allows the software to adjust the engine modes so that it delivers the maximum power for a specific situation, but at the same time uses the minimum amount of gasoline. While most motorists see this as a concern for their wallets, in fact, poor fuel combustion increases the level of exhaust pollution. All manufacturers primarily rely on this indicator.

The microprocessor calculates the number of openings of the nozzles to determine the fuel consumption. Of course, this indicator is relative, since the electronics cannot perfectly calculate how much fuel passed through the nozzles of the injectors in those fractions of a second while they were open.

Additionally, modern cars are equipped with an adsorber. This device is installed on a closed gasoline vapor circulation system of the fuel tank. Everyone knows that gasoline tends to evaporate. To prevent gasoline vapors from entering the atmosphere, the adsorber passes these gases through itself, filters them out and sends them to the cylinders for afterburning.

Electronic control unit

No forced petrol system works without an electronic control unit. This is a microprocessor into which the program is stitched. The software is developed by the automaker for a specific car model. The microcomputer is configured for a certain number of sensors, as well as for a specific algorithm of operation in case a sensor fails.

The microprocessor itself consists of two elements. The first one stores the main firmware - the manufacturer's setting or the software that is installed by the master during chip tuning (why it is needed is described in another article).

Fuel injection systems for engines

The second part of the ECU is the calibration block. This is an alarm circuit that is configured by the motor manufacturer in case the device does not capture a signal from a specific sensor. This element is programmed for a large number of variables that are activated when specific conditions are met.

Given the complexity of communication between the control unit, its settings and sensors, you should be attentive to the signals that appear on the instrument panel. In budget cars, when a problem occurs, the motor icon simply lights up. To identify a malfunction in the injection system, you will need to connect the computer to the ECU service connector and carry out diagnostics.

To facilitate this procedure, an on-board computer is installed in more expensive cars, which independently performs diagnostics and issues a specific error code. The decoding of such service messages can be found in the transport service book or on the manufacturer's official website.

Which injection is better?

This question arises among the owners of cars with the considered fuel systems. The answer to it depends on various factors. For example, if the price of the question is the economy of the machine, compliance with high environmental standards and maximum efficiency from the combustion of BTC, then the answer is unambiguous: direct injection is better, since it is closest to the ideal. But such a car will not be cheap, and due to the design features of the system, the motor will have a large volume.

But if a motorist wants to modernize his transport in order to increase the performance of the internal combustion engine by dismantling the carburetor and installing injectors, then he will have to stop at one of the distributed injection options (mono injection is not quoted, since this is an old development that is not much more efficient than a carburetor). Such a fuel system will have a low price, and it is also not so whimsical to the quality of gasoline.

Fuel injection systems for engines

Compared to a carburetor, forced injection has the following advantages:

  • The economy of transport increases. Even the first injector designs show a flow reduction of about 40 percent;
  • The power of the unit increases, especially at low speeds, thanks to which it is easier for beginners to use the injector to learn to drive;
  • To start the engine, fewer actions are required from the driver (the process is fully automated);
  • On a cold engine, the driver does not need to control the speed so that the internal combustion engine does not stall while it is warming up;
  • The dynamics of the motor increases;
  • The fuel supply system does not need to be adjusted, as this is done by the electronics, depending on the engine operating mode;
  • The control of the mixture composition is carried out, which increases the environmental friendliness of emissions;
  • Up to the Euro-3 level, the fuel system does not need scheduled maintenance (all that is needed is to change the failed parts);
  • It becomes possible to install an immobilizer in the car (this anti-theft device is described in detail separately);
  • In some car models, the engine compartment space is increased by removing the "pan";
  • The emission of gasoline vapors from the carburetor at low engine speeds or during a long stop is excluded, thereby reducing the risk of their ignition outside the cylinders;
  • In some carburetor machines, even a slight roll (sometimes 15 percent tilt is enough) can cause the engine to stop or inadequate carburetor operation;
  • The carburetor is also highly dependent on atmospheric pressure, which greatly affects engine performance when the machine is operated in mountainous areas.
Fuel injection systems for engines

Despite the clear advantages over carburetors, injectors still have some disadvantages:

  • In some cases, the cost of maintaining the system is very high;
  • The system itself consists of additional mechanisms that can fail;
  • Diagnostics requires electronic equipment, although certain knowledge is also required to properly adjust the carburetor;
  • The system is completely dependent on electricity, therefore, when upgrading the motor, the generator must also be replaced;
  • Errors can sometimes occur in an electronic system due to incompatibility between hardware and software.

Gradually tightening environmental standards, as well as a gradual rise in the price of gasoline, makes many motorists switch to vehicles with injection engines.

In addition, we suggest watching a short video on what a fuel system is and how each element works:

Vehicle fuel system. Device, operating principle and malfunctions!

Questions and answers:

What are the fuel injection systems? There are only two fundamentally different fuel injection systems. Monoinjection (analogue of a carburetor, only fuel is supplied by a nozzle). Multipoint injection (nozzles spray fuel into the intake manifold).

How does the fuel injection system work? When the intake valve opens, the injector sprays fuel into the intake manifold, the air-fuel mixture is sucked in naturally or thanks to turbocharging.

How does the fuel injection system work? Depending on the type of system, the injectors spray fuel either into the intake manifold or directly into the cylinders. The injection timing is determined by the ECU.

Чwhat injects gasoline into the engine? If the fuel system is distributed injection, then an injector is installed on each intake manifold pipe, the BTC is sucked into the cylinder due to the vacuum in it. If direct injection, then fuel is supplied to the cylinder.

One comment

  • About eye

    The article is cool, but it reads terribly, it sounds like someone would translate it with a google translator

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