One of the most important working systems of almost any car is the fuel injection system, because it is thanks to it that the volume of fuel is determined necessary for the engine at a specific point in time. Today we will consider the principle of operation of this system using the example of some of its types, as well as get acquainted with the existing sensors and actuators.
1. Features of the fuel injection system
On engines produced today, it has not been used for a long time carburetor system, which turned out to be completely supplanted by a newer and improved fuel injection system. Fuel injection is usually called a metered supply system. fuel fluid in the engine cylinders vehicle... It can be installed on both gasoline and diesel engines, however, it is clear that the design and principle of operation will be different. When used on gasoline engines, during injection, a homogeneous air-fuel mixture appears, which is forcibly ignited by the spark from the spark plug.
Concerning diesel type engine, then here fuel injection is carried out under very high pressure, moreover, the required portion of fuel is mixed with hot air and ignites almost immediately. The amount of fuel injected, and at the same time the total engine power, is determined by the injection pressure. Therefore, the higher the pressure, the higher the power of the power unit becomes.
Today, there is a fairly significant amount of species diversity of this system, and the main species include: a system with direct injection, with mono injection, mechanical and distributed system.
The principle of operation of the direct (direct) fuel injection system is that the fuel fluid, using injectors, is fed directly into the engine cylinders (for example, like a diesel engine). For the first time such a scheme was used in military aviation during the Second World War and on some cars. post-war period(the first was the Goliath GP700). However, the direct injection system of that time could not gain the due popularity, the reason for which was the expensive high-pressure fuel pumps required for operation and the original cylinder head.
As a result, the engineers did not succeed in achieving operational accuracy and reliability from the system. Only at the beginning of the 90s of the twentieth century, due to the tightening of environmental standards, the interest in direct injection began to grow again. Among the first companies to launch the production of such engines were Mitsubishi, Mercedes-Benz, Peugeot-Citroen, Volkswagen, BMW.
In general, direct injection could be called the peak of the evolution of power systems, if not for one thing ... Such engines are very demanding in terms of fuel quality, and when using lean mixtures, they also strongly emit nitrogen oxide, which has to be dealt with by complicating the design of the engine ...
Single-point injection (also called "mono-injection" or "central injection") is a system that in the 80s of the twentieth century began to be used as an alternative to the carburetor, especially since the principles of their operation are very similar: air flows are mixed with fuel liquid during intake manifold, that's just to replace the complex and sensitive to the settings of the carburetor, the nozzle came. Of course, at the initial stage of the development of the system, there was no electronics at all, and the supply of gasoline was controlled mechanical devices... However, despite some drawbacks, the use of injection still provided the engine with much more high rates power and significantly greater fuel efficiency.
And all thanks to the same nozzle, which made it possible to meter fuel liquid much more accurately, spraying it into small particles. As a result of the mixture with air, a homogeneous mixture was obtained, and when the driving conditions of the car and the operating mode of the engine changed, its composition changed almost instantly. True, there were also some drawbacks. For example, since, in most cases, the nozzle was installed in the body former carburetor, and bulky sensors made it difficult to "breathe the motor", the air flow entering the cylinder met serious resistance. From a theoretical point of view, such a deficiency could be easily eliminated, but with the existing bad distribution fuel mixture, no one could do anything then. This is probably why, in our time, single point injection so rare.
The mechanical injection system appeared at the end of the 30s of the twentieth century, when it began to be used in aircraft fuel supply systems. It was presented in the form of a gasoline injection system of diesel origin, using high-pressure fuel pumps and closed injectors of each individual cylinder. When they tried to install them on a car, it turned out that they could not withstand the competition of carburetor mechanisms, and the reason for this was the significant complexity and high cost of the design.
For the first time, a low pressure injection system was installed on a MERSEDES car in 1949 and after operational characteristics immediately surpassed the carburetor-type fuel system. This fact gave impetus to the further development of the idea of gasoline injection for cars equipped with an internal combustion engine. From point of view pricing policy and reliability in operation, the most successful in this regard, is the mechanical system "K-Jetronic" from BOSCH. Her serial production was established back in 1951 and it, almost immediately, became widespread in almost all brands of European automobile manufacturers.
The multi-point (distributed) version of the fuel injection system differs from the previous ones by the presence of an individual nozzle, which was installed in the inlet pipe of each individual cylinder. Its task is to supply fuel directly to the intake valve, which means preparing the fuel mixture right before it enters the combustion chamber. Naturally, under such conditions, it will have a homogeneous composition and approximately the same quality in each of the cylinders. As a result, the power of the engine, its fuel efficiency is significantly increased, and the level of toxicity of exhaust gases is also reduced.
On the way of system development distributed injection fuel sometimes encountered certain difficulties, however, she still continued to improve. At the initial stage, it, like the previous version, was controlled mechanically, however, the rapid development of electronics, not only made it more efficient, but also gave a chance to coordinate actions with the rest of the motor structure. So it turned out that modern engine is able to signal the driver about a malfunction, if necessary, independently switch to emergency operating mode or, having enlisted the support of security systems, correct individual errors in management. But all this, the system performs with the help of certain sensors, which are designed to record the slightest changes in the activity of one or another part of it. Let's consider the main ones.
2. Sensors of the fuel injection system
Fuel injection system sensors are designed to record and transmit information from actuators to the engine control unit and vice versa. These include the following devices:
Its sensing element is located in the flow of exhaust (exhaust) gases, and when working temperature reaches 360 degrees Celsius, the sensor begins to generate its own EMF, which is directly proportional to the amount of oxygen in the exhaust gases. Practically speaking, when the loop feedback closed, the oxygen sensor signal is a rapidly changing voltage between 50 and 900 millivolts. The possibility of changing the voltage is caused by a constant change in the composition of the mixture near the stoichiometric point, and the sensor itself is not adapted to generate an alternating voltage.
Depending on the power supply, two types of sensors are distinguished: with pulse and constant power supply of the heating element. In the pulse version, the oxygen sensor is heated by the electronic control unit. If it is not warmed up, then it will have a high internal resistance, which will not allow generating its own EMF, which means that the control unit will "see" only the specified stable reference voltage. As the sensor warms up, its internal resistance decreases and the process of generating its own voltage begins, which immediately becomes known to the ECU. For the control unit, this is a signal of readiness for use in order to adjust the composition of the mixture.
Used to obtain an estimate of the amount of air that enters the engine of the machine. It is part of the electronic engine management system. This device can be used in conjunction with some other sensors, such as an air temperature sensor and an atmospheric pressure sensor, which correct its readings.
The air flow sensor contains two platinum filaments heated by electric current. One thread passes air through itself (cooling in this way), and the second is a control element. Using the first platinum filament, the amount of air that has entered the engine is calculated.
Based on the information received from the air flow sensor, the ECU calculates the required volume of fuel required to maintain the stoichiometric ratio of air and fuel in the specified operating conditions of the engine. In addition, the electronic unit uses the information received to determine the operating point of the motor. Today there are several different types sensors responsible for mass flow air: for example, ultrasonic, vane (mechanical), hot-wire, etc.
Coolant temperature sensor (DTOZH). It has the form of a thermistor, that is, a resistor in which the electrical resistance can vary depending on temperature indicators... The thermistor is located inside the sensor and expresses a negative coefficient of resistance of temperature indicators (with heating, the resistance force decreases).
Accordingly, at a high coolant temperature, there is a low resistance of the sensor (about 70 ohms at 130 degrees Celsius), and at a low temperature - high (about 100800 ohms at -40 degrees Celsius). Like most other sensors, this device does not guarantee accurate results, which means talking about the dependence of resistance temperature sensor coolant from temperature indicators can only be approximately. In general, although the described device practically does not break down, it is sometimes seriously "mistaken".
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It is mounted on the throttle pipe and is connected to the axis of the damper itself. It is presented in the form of a potentiometer with three ends: one is supplied with positive power (5V), and the other is connected to ground. The third pin (from the slider) carries the output signal to the controller. When the throttle valve is rotated when the pedal is depressed, the output voltage of the sensor changes. If the throttle valve is in the closed state, then, accordingly, it is below 0.7 V, and when the throttle begins to open, the voltage rises and in the fully open position should be more than 4 V. Following the output voltage of the sensor, the controller, depending on the angle discoveries throttle, makes a correction to the fuel supply.
Considering that the controller himself determines minimum voltage device and takes it as zero, this mechanism does not need adjustment. According to some motorists, the throttle position sensor (if it is domestic production) Is the most unreliable element of the system, requiring periodic replacement (often after 20 kilometers). Everything would be fine, but it is not so easy to make a replacement, especially if you do not have a high-quality tool with you. It's all about the fastening: the bottom screw is unlikely to be unscrewed with an ordinary screwdriver, and if it does, it is quite difficult to do it.
In addition, when screwing in at the factory, the screws are "set" on a sealant, which "seals" so much that when unscrewing the cap often breaks off. In this case, it is recommended to completely remove the entire throttle assembly, and in the worst case, you will have to pick it out by force, but only if you are completely sure that it is inoperative.
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Serves to transmit to the controller a signal about the speed and position of the crankshaft. This signal is a series of repeated electrical voltage pulses that are generated by the sensor during rotation. crankshaft... Based on the received data, the controller can control the injectors and the ignition system. The crankshaft position sensor is installed on the cover oil pump, at a distance of one millimeter (+ 0.4mm) from the crankshaft pulley (has 58 teeth located in a circle).
To ensure the possibility of generating a "synchronization pulse", two pulley teeth are missing, that is, in fact, there are 56 of them. When it rotates, the disc teeth change the magnetic field of the sensor, thereby creating a pulse voltage. Based on the nature of the pulse signal coming from the sensor, the controller can determine the position and speed of the crankshaft, which makes it possible to calculate the moment when the ignition module and injectors are triggered.
The crankshaft position sensor is the most important of all those listed here and in the event of a malfunction of the mechanism, the car engine will not work. Speed sensor. The principle of operation of this device is based on the Hall effect. The essence of its work is to transmit voltage pulses to the controller, with a frequency directly proportional to the speed of rotation of the driving wheels of the vehicle. Based on the connectors on the harness block, all speed sensors may have some differences. So, for example, a square-shaped connector is used in Bosch systems, and a round one corresponds to January4 and GM systems.
Based on the outgoing signals from the speed sensor, the control system can determine fuel cut-off thresholds, as well as set electronic speed limits for the vehicle (available in new systems).
Position sensor camshaft (or as it is also called "phase sensor") is a device designed to determine the angle of the camshaft and transmit the corresponding information to the electronic control unit of the vehicle. After that, based on the data received, the controller can control the ignition system and the fuel supply to each individual cylinder, which, in fact, he does.
Knock sensor It is used to search for knocking shocks in an internal combustion engine. From a constructive point of view, it is a piezoceramic plate enclosed in a housing, located on the cylinder block. Nowadays, there are two types of knock sensor - resonant and more modern broadband. In resonant models, the primary filtering of the signal spectrum is carried out inside the device itself and directly depends on its design. Therefore, on different types engine are used different models knock sensors that differ from each other in resonance frequency. The broadband type of sensors has a flat characteristic in the knock noise range, and the signal is filtered by the electronic control unit. Today, resonant knock sensors are no longer installed on serial models cars.
Sensor absolute pressure. Monitors changes in atmospheric pressure that occur as a result of changes in barometric pressure and / or changes in altitude. The barometric pressure can be measured during ignition on, before the engine starts to crank. With the help of the electronic control unit, it is possible to "update" the barometric pressure data when the engine is running, when, at low engine speed, the throttle valve is almost completely open.
Also, using an absolute pressure sensor, it is possible to measure the change in pressure in the intake pipe. Changes in pressure are caused by changes in engine loads and crankshaft speed. The absolute pressure sensor converts them into an output signal with a specific voltage. When the throttle is in the closed position, the absolute pressure output appears to give a comparatively low voltage, while a fully open throttle valve corresponds to a high voltage signal. The high output voltage is due to a match between atmospheric pressure and the pressure inside the intake pipe at full throttle. Indicators internal pressure pipes are calculated electronic unit control based on the sensor signal. If it turns out that it is high, then an increased supply of fuel fluid is required, and if the pressure is low, then on the contrary - a reduced one.
(ECU). Although this is not a sensor, given that it is directly related to the operation of the described devices, we considered it necessary to add it to this list... The ECU is the "brain center" of the fuel injection system, which constantly processes information data received from various sensors and, on the basis of this, controls the output circuits (systems electronic ignition, injectors, idle speed regulator, different relays). The control unit is equipped with a built-in diagnostic system capable of recognizing system malfunctions and, using control lamp"CHECK ENGINE", warn the driver about them. Moreover, in his memory are stored diagnostic codes that indicate specific areas of failure, making repairs much easier.
The ECU includes three types of memory: read only memory device with programmability (RAM and EPROM), random access memory (RAM or RAM) and memory device subject to electrical programming (EPROM or EEPROM). RAM is used by the microprocessor of the unit for temporary storage of measurement results, calculations and intermediate data. This type of memory depends on energy supply, which means that it requires constant and stable power supply to store information. In the event of a power outage, all diagnostic trouble codes and calculation information available in RAM are immediately erased.
The EPROM stores the total work program which contains the sequence of required commands and various calibration information. Unlike the previous option, given view memory is not volatile. EEPROM is used to temporarily save the password codes of the immobilizer (anti-theft automotive system). After the controller has received these codes from the immobilizer control unit (if any), they are compared with those already stored in the EEPROM, and then, a decision is made to enable or disable the start of the motor.
3. Actuators of the injection system
The actuators of the fuel injection system are presented in the form of an injector, a fuel pump, an ignition module, an idle speed regulator, a cooling system fan, a fuel consumption signal and an adsorber. Let's consider each of them in more detail. Nozzle. Fulfills the role solenoid valve with standardized performance. Used to inject a certain amount of fuel, calculated for a specific operating mode.
Gasoline pump. It is used to move fuel into the fuel rail, the pressure in which is maintained by means of a vacuum-mechanical pressure regulator. In some versions of the system, it can be combined with a gas pump.
Ignition module is electronic device designed to control the sparking process. Consists of two independent channels for igniting the mixture in the engine cylinders. In the latest, modified versions of the device, its low-voltage elements are defined in the ECU, and to obtain high voltage, either a two-channel remote ignition coil is used, or those coils that are located directly on the plug itself.
Idling regulator. Its task is to maintain the specified idle speed. The regulator is a stepper motor driving a bypass air channel in the throttle body. This provides the motor with the necessary airflow to operate, especially when the throttle valve is closed. Fan cooling system, as the name suggests, prevents parts from overheating. It is controlled by an ECU that reacts to signals from the coolant temperature sensor. Typically, the difference between the on and off positions is 4-5 ° C.
Fuel consumption signal- goes to trip computer in the ratio of 16000 impulses per 1 calculated liter of fuel used. Of course, these are only approximate figures, because they are calculated based on the total time spent opening the injectors. In addition, a certain empirical coefficient is taken into account, which is needed to compensate for the assumption in the measurement of the error. Inaccuracies in the calculations are caused by the operation of the injectors in the non-linear section of the range, asynchronous fuel efficiency and some other factors.
Adsorber. It exists as an element of a closed circuit during the recirculation of gasoline vapors. Euro-2 standards exclude the possibility of contact of the gas tank ventilation with the atmosphere, and gasoline vapors must be adsorbed and sent for afterburning during blowing.
Slightly different from gasoline counterparts. The main difference can be considered the ignition of the fuel-air mixture, which does not occur from external source(ignition sparks), but from strong compression and heat.
In other words, the fuel spontaneously ignites in a diesel engine. In this case, the fuel must be supplied under extremely high pressure, since it is necessary to spray the fuel in the cylinders of the diesel engine as efficiently as possible. In this article, we will talk about which injection systems for diesel engines are actively used today, and also consider their design and principle of operation.
Read in this article
How the fuel system of a diesel engine works
As mentioned above, a diesel engine self-ignites a working mixture of fuel and air. In this case, at first only air is supplied to the cylinder, then this air is strongly compressed and heats up from the compression. For a fire to occur, feed towards the end of the compression stroke.
Given that air is highly compressed, the fuel must also be injected at high pressure and atomized efficiently. In different diesel pressure injection can differ, starting from an average of 100 atmospheres and ending with an impressive indicator of more than 2 thousand atmospheres.
For the most efficient fuel supply and optimal conditions for self-ignition of the charge with subsequent full combustion of the mixture, fuel injection is implemented through a diesel injector.
It turns out, no matter what type of power system is used, there are always two main elements in diesel engines:
- device for creating high fuel pressure;
In other words, on many diesel engines, the pressure creates ( fuel pump high pressure), and diesel fuel is supplied to the cylinders through injectors. As for the differences, in different systems The fuel supply pump can have one or another design; the diesel injectors themselves also differ in their design.
Also, power systems may differ in the location of certain constituent elements have different schemes management, etc. Let's take a closer look at the injection systems of diesel engines.
Diesel engine power systems: an overview
If we divide the power systems of diesel engines, which received most widespread, the following solutions can be distinguished:
- The power system, which is based on in-line injection pump (in-line injection pump);
- The fuel supply system, which has a distribution type injection pump;
- Solutions with unit injectors;
- Fuel injection Common rail(high pressure accumulator in the common line).
These systems also have a large number of subspecies, and in each case one or another type is the main one.
- So, let's start with the simplest scheme, which assumes the presence of an in-line fuel pump. In-line injection pump is a well-known and proven solution that has been used on diesel engines for more than a dozen years. Such a pump is actively used on special equipment, trucks, buses, etc. Compared to other systems, the pump is quite large in size and weight.
In a nutshell, in-line injection pumps are based on. Their number is equal to the number of engine cylinders. The plunger pair is a cylinder that moves in a "glass" (sleeve). When moving upwards, the fuel is compressed. Then, when the pressure reaches the required value, a special valve opens.
As a result, the pre-compressed fuel enters the injector and is then injected. After the plunger starts to move back down, the fuel inlet port opens. Through the channel, the fuel fills the space above the plunger, then the cycle is repeated. In order for the diesel fuel to get into the plunger pairs, there is additionally a separate booster pump in the system.
The plungers themselves work due to the fact that there is a camshaft in the pump device. This shaft works similarly where the cams "push" the valve. The pump shaft itself is driven by the engine, since the injection pump is connected to the motor by means of an injection advance clutch. The specified clutch allows you to adjust the operation and adjust the injection pump during engine operation.
- The power supply system with a distribution pump does not differ much from the scheme with an in-line injection pump. Distribution injection pump is similar to in-line in design, while the number of plunger pairs is reduced in it.
In other words, if in an in-line pump, pairs are needed for each cylinder, then in a distribution pump, 1 or 2 plunger pairs are enough. The fact is that one pair in this case is enough to supply fuel to 2, 3 or even 6 cylinders.
This became possible due to the fact that the plunger was able to not only move up (compression) and down (inlet), but also rotate around the axis. This rotation made it possible to realize the alternate opening of the outlet openings through which diesel fuel is supplied under high pressure to the injectors.
Further development of this scheme led to the emergence of a more modern rotary injection pump. In such a pump, a rotor is used, in which plungers are installed. These plungers move towards each other, and the rotor rotates. This is how the diesel fuel is compressed and distributed over the engine cylinders.
The main advantage of the distribution pump and its variants is the reduced weight and compactness. At the same time, it is more difficult to configure this device. For this reason, schemes are additionally used electronic control and adjustments.
- The "pump-injector" type power system is a circuit where a separate high-pressure fuel pump is initially absent. More specifically, the nozzle and pump section were combined in one housing. It is based on the already familiar plunger pair.
The solution has a number of advantages over systems that use a high-pressure fuel pump. First of all, the fuel supply to the individual cylinders can be easily adjusted. Also, if one injector fails, the rest will work.
Also, the use of unit injectors allows you to get rid of a separate drive for the injection pump. The plungers in the unit injector are driven by the timing camshaft, which is installed in. These features allowed pump-nozzle diesel engines to become widespread not only on trucks, but also on large passenger cars (for example, diesel SUVs).
- The Common Rail system is one of the most modern solutions in the area of fuel injection. Also this scheme power supply allows you to achieve maximum efficiency at the same time with high. At the same time, the toxicity of the exhaust gases is also reduced.
The system was developed by the German company Bosch in the 90s. Given the obvious advantages in a short time, the vast majority diesel internal combustion engines on cars and trucks began to equip exclusively with Common Rail.
The general design of the device is based on a so-called high pressure accumulator. To put it simply, the fuel is under constant pressure, after which it is supplied to the nozzles. As for the pressure accumulator, given battery in fact, it is a fuel line, where fuel is pumped using a separate high-pressure fuel pump.
The Common Rail system partially resembles a gasoline injection engine, which has a fuel rail with injectors. Gasoline is pumped into the rail (fuel rail) under low pressure from the fuel pump from the tank. In a diesel engine, the pressure is much higher, the fuel is pumped by the high-pressure fuel pump.
Due to the fact that the pressure in the accumulator is constant, it became possible to realize fast and "multi-layer" fuel injection through the injectors. Modern systems in Common Rail engines allow the injectors to make up to 9 metered injections.
As a result, a diesel engine with such a power system is economical, efficient, works softly, quietly and flexibly. Also, the use of a pressure accumulator made it possible to make the design of the injection pump on diesel engines simpler.
We add that high-precision injection on Common Rail engines is completely electronic, since a separate control unit monitors the operation of the system. The system uses a group of sensors that allow the controller to accurately determine how much diesel fuel needs to be supplied to the cylinders and at what moment.
Let's summarize
As you can see, each of the considered diesel engine power systems has its own advantages and disadvantages. If we talk about the simplest solutions with in-line injection pump, their main advantage can be considered the possibility of repair and availability of service.
In circuits with unit injectors, it must be remembered that these elements are sensitive to the quality of the fuel and its purity. The ingress of even the smallest particles can damage the unit injector, as a result of which an expensive element will need to be replaced.
Concerning Common systems Rail, the main disadvantage is not only the high initial cost of such solutions, but also the complexity and high cost of subsequent repair and maintenance. For this reason, fuel quality and condition fuel filters you need to constantly monitor, as well as carry out scheduled maintenance in a timely manner.
Read also
Views diesel injectors in different fuel supply systems under high pressure. Principle of operation, methods of injector control, design features.
Many modern injection engines are equipped with various fuel injection systems. Mono injection, and even more so the carburetor, has long gone into history, and now there are two main types - the distributed and direct type (on many cars they are "hidden" under the abbreviations MPI and GDI). However, a common man in the street really does not understand what the difference is, and also which one is better. Today we will close this gap at the end there will be a video version and voting, so read-watch-vote ...
You really came to the salon, you look at the configuration, and there are solid MPI or GDI, there may also be TURBO options. You start asking a consultant, and he definitely praises direct injection, but distributed injection (well, if you don't have enough money). BUT why is he so good then? Why overpay, and is it spent on it?
Distributed or multi-point fuel injection
Let's start with him, all because he appeared first (in front of his opponent). Prototypes existed at the dawn of the 20th century, although they were far from ideal and often used mechanical control.
Abbreviation MPI (Multi Point Injection) - multipoint distributed injection. In fact, this is a modern injector.
Now, with the development of electronics, the carburetor and other power systems that were at the dawn are becoming a thing of the past. Distributed injection is an electronic power system, which is based on injectors (from the word injection), a fuel rail (where they are installed), an electronic pump (which is attached to the tank). It's just that the ECU gives orders to the pump to pump fuel, it goes along the highway to the fuel rail, then to the injector and then sprayed at the level.
But this system has also been polished over the years. There are three types of injection:
- Simultaneous ... Previously, in the 70s and 80s, no one cared about the price of gasoline (it was cheap), and no one thought about the environment either. Therefore, fuel was injected into all cylinders at once, with one revolution of the crankshaft. It was extremely impractical, because as usual (at 4 cylinder engine) - two pistons work on compression, while the other two take off exhaust gases. And if you supply gasoline to all the "pots" at once, then the other two will simply throw it into the muffler. It is extremely costly in terms of gasoline and is very harmful to the environment.
- Parallel pair ... This kind of distribution injection, as you probably already guessed, took place in two cylinders in turn. That is, the fuel went exactly where the compression is now taking place.
- Phased type ... It is the most perfect on this moment method, here each nozzle lives "its own life" and is controlled separately. It delivers gas just before the intake stroke. This is where the maximum economy of the mixture takes place, as well as a high environmental component.
I think with this it is clear, it is the third type that is now being installed on everything modern models cars.
WHERE IS THE INJECTOR ... This is where the main difference between distributor injection and direct injection lies. The injector is at the level of the intake manifold, next to the engine block.
The mixing of air and gasoline takes place precisely in the manifold. Metered air comes from the throttle valve (which you regulate with the gas pedal), when it reaches the nozzle, fuel is injected, a mixture is obtained, which is already drawn through the intake valves into the engine cylinders (further compression, ignition and exhaust gas discharge).
PLUSES such a method can be called the relative simplicity of the design, low cost, also the injectors themselves should not be complex and resistant to high temperatures (because I have no contact with the combustible mixture), they work longer without cleaning, they are not so demanding on the quality of the fuel.
MINUSES more fuel consumption (compared to the opponent), less power
BUT, due to simplicity, low cost and unpretentiousness, they are installed on a large number of motors, not only budget segment but also D-class.
It appeared not so long ago, in the 80s - 90s of the last century. Such brands as MERCEDES, VOLKSWAGEN, BMW, etc. were actively involved in development.
Abbreviation GDI (Gasoline Direct Injection) - injection directly into the combustion chamber
The injection takes place according to the phased-type principle, that is, each injector is controlled separately. Often they are fixed in a high pressure rail (something like a COMMON RAIL), but there are also individual elements fuel is suitable for each separately.
WHAT IS THE DIFFERENCE HERE - the injectors are screwed into the engine block itself and have direct contact with the combustion chamber and the ignited fuel mixture.
Air is also supplied through the throttle, then through the intake manifold - through the valves it enters the engine cylinders, after which fuel is injected during the compression cycle, mixing with air and igniting from the spark plug. That is, the mixture takes place directly in the engine, and not in the intake manifold, this is the main DIFFERENCE!
PROS. Fuel efficiency (can reach up to 10%), high power(up to 5%), better ecology.
MINUSES ... You need to understand the nozzle is next to the ignited mixture, it follows from this:
- Complex construction
- Complex service
- Expensive repair and maintenance
- Requirement for fuel quality (otherwise it will be clogged)
As you can see, it is efficient and technologically efficient, but expensive to maintain.
Which is better - a table?
I propose to think about it, made a table on the advantages of both types
As you can see, both types have significant advantages over the other, apparently while both exist.
Now we are watching the video version.
On modern cars are used various systems fuel injection. The injection system (another name - injection system, from injection - injection), as the name suggests, provides fuel injection.
The injection system is used on both gasoline and diesel engines. However, the design and operation of injection systems for gasoline and diesel engines differ significantly.
In gasoline engines, injection forms a homogeneous fuel-air mixture, which is forcedly ignited by a spark. In diesel engines, fuel is injected at 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 part of fuel system of the car. The main working element of any injection system is the injector ( injector).
Petrol injection systems
Depending on the method of forming the fuel-air mixture, the following systems are distinguished central injection, multipoint injection and direct injection. Central and multipoint 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 feature low level noise and smooth operation. But nowadays, direct injection systems are preferred. In spite of elevated level noise, such systems have high fuel efficiency.
The defining structural element of the injection system of a diesel engine is the high-pressure fuel pump (injection pump).
On cars with diesel engine are installed various designs injection systems: with in-line injection pump, with distribution injection pump, pump nozzles, Common Rail. Progressive systems injection - unit injectors and the Common Rail system.
»Fuel injection system - diagrams and principle of operation
Different systems and types of fuel injection.
Fuel injector Is nothing more than an automatic controlled valve. Fuel injectors are part of a mechanical system that injects fuel into the combustion chambers at regular intervals. Fuel injectors able to open and close many times within one second. In recent years, previously used carburetors for fuel delivery have been largely replaced by injectors.
- Throttle and damper injector.
The throttle body is the simplest type of injection. Like the carburetors, the throttle injector is located on top of the engine. These injectors are very much like carburetors except for their function. Like carburetors, they don't have a bowl of fuel or jets. In this form, the injectors transfer it directly to the combustion chambers.
- Continuous injection system.
As the name suggests, there is a continuous flow of fuel from the injectors. Its entry into cylinders or tubes is controlled by intake valves... There is a continuous flow of fuel at a variable rate in continuous injection.
- Central injection port (CPI).
This circuit uses a special type of fittings called 'valve poppets'. Valve poppets are the valves used to control the inlet and outlet of fuel to the cylinder. This sprays fuel at every shot using a tube attached to a central injector.
- Multi-port or multi-point fuel injection - scheme of work.
One of the more advanced fuel injection schemes these days is called 'multipoint or multi-port injection'. This is a dynamic type of injection that contains separate nozzle for each cylinder. In a multi-port fuel injection system, all injectors spray it simultaneously without any delay. Simultaneous multipoint injection is one of the most advanced mechanical settings that allows the fuel in the cylinder to instantly ignite. Hence, with multi-point fuel injection, the driver will get a quick response.
Modern fuel injection schemes are quite complex computerized mechanical systems which boil down not only to fuel injectors. The whole process is controlled by a computer. AND various details react according to these instructions. There are a number of sensors that adapt by sending important information computer. There are various sensors that monitor fuel consumption, oxygen levels, and others.
Although this fuel system diagram is more complex, its operation different parts very refined. It helps control oxygen levels and fuel consumption, which helps to avoid unnecessary fuel consumption in the engine. The fuel injector gives your car the potential to perform tasks with a high degree of precision.
For different fuel systems, it is often necessary to flush with special equipment.
The essence of the scheme of direct injection into the combustion chamber
For a person who does not have a technical mindset, understanding this issue is an extremely difficult task. But still, knowledge of the differences between this engine modification from an injection or carburetor one is necessary. For the first time, direct injection engines were used in Mercedes-Benz models 1954 release, but great popularity this modification acquired through Mitsubishi under the name Gasoline Direct Injection.
And since then, this design has been used by many famous brands, such as:
- Infinity,
- Ford,
- General Motors,
- Hyundai,
- Mercedes-Benz,
- Mazda.
Moreover, each of the firms uses its own name for the system under consideration. But the principle of operation remains the same.
The growth in popularity of the fuel injection system is facilitated by the indicators of its efficiency and environmental friendliness, since when using it, emissions are significantly reduced harmful substances in atmosphere.
Main features of the fuel injection system
The basic principle of this system is that fuel is injected directly into the engine cylinders. The system usually requires two fuel pumps to operate:
- the first is located in the tank with gasoline,
- the second is on the engine.
Moreover, the second is a high-pressure pump, sometimes delivering more than 100 bar. This is a necessary condition for operation, since fuel enters the cylinder during the compression stroke. High pressure is the main reason for the special structure of the nozzles, which are made in the form of Teflon O-rings.
This fuel system, unlike a conventional injection system, is an internal mixing system with a stratified or uniform formation of an air-fuel mass. The mixture formation method changes with changing engine load. We will understand the operation of the engine with a layer-by-layer and homogeneous formation air-fuel mixture.
Work with stratified fuel mixture
Due to the structural features of the collector (the presence of dampers that close the bottom), access to the bottom is blocked. On the intake stroke, air enters the upper part cylinder, after some rotation of the crankshaft on the compression stroke, fuel is injected, which requires high pump pressure. Next, the resulting mixture is blown away by an air vortex to the candle. At the moment the spark is applied, gasoline will already be well mixed with air, which contributes to high-quality combustion. At the same time, the air gap creates a kind of shell, which reduces losses and increases the efficiency, thereby reducing fuel consumption.
It should be noted that work with stratified fuel injection is the most promising direction, since in this mode the most optimal fuel combustion can be achieved.
Homogeneous fuel mixture formation
In this case, the ongoing processes are even easier to understand. The fuel and the air required for combustion almost simultaneously enter the engine cylinder during the intake stroke. Even before the piston reaches top dead point the air-fuel mixture is in a mixed state. The formation of a high-quality mixture is due to high pressure injection. The system switches from one operating mode to another thanks to the analysis of the incoming data. As a result, this leads to an increase in the economy of the engine.
The main disadvantages of fuel injection
All the advantages of a direct fuel injection system are only achieved when using petrol that meets certain quality criteria. They should be sorted out. System octane requirements great features Dont Have. Good cooling of the air-fuel mixture is also achieved when using gasoline with octane numbers from 92 to 95.
The most stringent requirements are put forward precisely to the purification of gasoline, its composition, the content of lead, sulfur and dirt. There should be no sulfur at all, since its presence will lead to quick wear fuel equipment and failure of electronics. The disadvantages also include the increased cost of the system. This is due to the increasing complexity of the design, which in turn leads to an increase in the cost of components.
Outcomes
Analyzing the above information, it is safe to say that the system with direct injection of fuel into the combustion chamber is more promising and modern than injection with distribution. It allows you to significantly increase the efficiency of the engine due to High Quality air-fuel mixture. The main disadvantage of the system is the presence of high requirements for the quality of gasoline, the high cost of repair and maintenance. And when using low quality gasoline, the need for more frequent repairs and maintenance increases dramatically.
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