Injectors for diesel engines– these are the parts of fuel equipment that are most susceptible to wear. They are considered the easiest to maintain and carry out diagnostics in service centers. The quality of fuel combustion in the engine cylinders, its starting, vehicle acceleration dynamics, efficiency and the amount of harmful emissions depend on how efficiently the injectors work.
Injectors for diesel engines - what are they?
Depending on the type of nozzles and fuel system, the maximum pressure of diesel engine injectors in the nozzle at the moment of injection is about 200 MPa, and the time is from 1 to 2 milliseconds. The quality of injection determines the engine noise level, the amount of emissions of soot, nitrogen oxides and hydrocarbons into the atmosphere.
Modern models differ in the shape of the body, the size of the nozzles, and also in the control method. The difference between different types of injectors is the use of different injection systems and types of nozzles, which are pin and hole. Pin ones are used in engines with a pre-chamber ignition system, while hole type ones are installed on diesel engines with direct fuel injection.
According to the control method, parts are divided into single-spring, double-spring, with needle position control sensors and controlled by piezoelectric elements. Among other things, the design of a diesel engine injector depends on the method of its installation in the head: using a flange, a clamp, or by screwing it into a socket.
The principle of operation of a diesel engine injector - briefly about the complex
The main purpose of such parts is to meter and atomize fuel, as well as hermetically seal the combustion chamber. As a result of research, pump injectors were developed, which are installed in each cylinder separately. The operating principle of the new type of diesel engine injector is that it operates from the camshaft cam through a pusher. Fuel is supplied and drained through special channels in the cylinder head. Fuel dosing occurs through the control unit, which sends signals to the shut-off solenoid valves.
The pump injector operates in pulse mode, which allows for preliminary fuel supply before the main injection. As a result, engine operation is significantly softened and the level of toxic emissions is reduced.
Fuel injectors in most cases require simple maintenance; most often, in order to return them to working condition, it is enough to simply clean and rinse them. Regardless of how many injectors there are in the engine, it happens that when you press the gas pedal sharply, jerks and dips are felt or the power is noticeably reduced, the engine begins to operate unstably at low speeds, which means that the injector channels are clogged with hard tarry deposits. What to do?
Flushing diesel engine injectors - implementation methods
Contamination of this element leads to disruption of fuel atomization and leads to improper formation of the air-fuel mixture. Ideally, spraying should be as uniform as possible. The main source of pollution is the resins contained in the fuel. Flushing diesel engine injectors can eliminate all fuel supply problems.
The injector cleaning process involves removing various contaminants in the fuel channels. Currently, several methods are used:
- cleaning diesel engine injectors using ultrasound;
- flushing injectors with fuel with the addition of special additives;
- washing using special liquids on stands;
- hand washing.
For motorists, the last option is the most acceptable, since it allows you to carry out work on cleaning injectors at home. However, in advanced cases, you have to turn to the services of auto centers, where cleaning is carried out using ultrasound, which is a more severe method. It is recommended to resort to this type of cleaning only if washing with special liquids does not give a positive result.
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 the electronic control of the ECU - it is the on-board computer that supplies exactly the right amount of fuel into 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:
- controls the fuel mixture,
- controls idle speed,
- is responsible for the ignition timing angle,
- 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. An electric fuel pump usually 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 for 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 directly to the cylinders, but first to the intake manifolds.
How does an injector work?
But how does the ECU determine how much fuel currently needs 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 throttle opening value, but is not limited to this indicator - it reads information from many sensors, and let’s find out about them all!
Mass air flow sensor
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 electrical network of the car 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.
Injectors are the main element of diesel engines and gasoline engines with a fuel injection system (injectors). Today, there are several fundamentally different types of injectors that are used in engines of various designs. Read about all this in the presented article.
Purpose and types of nozzles
Diesel and injection gasoline engines use fuel injection systems, in which the main role is played by injectors - special devices that spray fuel in the combustion chamber. The operation of gasoline and diesel injectors is based on the same principle: fuel is atomized, passing under high pressure through a specially shaped nozzle (they create a fuel torch in which liquid fuel is broken into microscopic droplets and mixed with air).
However, the injectors of injection gasoline engines operate under a relatively low pressure of a few atmospheres, while the injectors of diesel engines operate under a pressure of hundreds and sometimes thousands of atmospheres.
Today, four types of nozzles are used:
Mechanical;
- Electromagnetic (electromechanical);
- Electrohydraulic;
- Piezoelectric.
Each type of nozzle has its own characteristics and areas of application.
Mechanical injectors
A mechanical nozzle is a “classic” solution that has been used for many decades and does not lose its relevance today. A mechanical injector is essentially a valve that opens when a certain pressure is reached. The basis of such a nozzle is a body, inside of which there is a needle, which, under the action of a spring, closes the nozzle. Fuel from the injection pump under pressure enters the annular chamber between the body and the needle and lifts the needle - at this moment the nozzle opens and the fuel is sprayed into the combustion chamber. When the pressure decreases, the needle closes the nozzle again.
The mechanical injector is very simple and reliable, but it cannot provide the performance required of modern diesel engines. Therefore, it is gradually being replaced by other types of nozzles.
An electromagnetic injector differs from a mechanical one in that the needle in it rises under the action of a built-in electromagnet based on a signal from the controller. The electromagnet is usually located at the top of the nozzle, the needle is connected to the armature of the electromagnet, so when voltage is applied, it rises up and opens the nozzle.
Today, conventional electromagnetic injectors are used on injection gasoline engines, as they do not work well under the high pressures required for diesel engines.
The electro-hydraulic injector combines the advantages of electromagnetic and mechanical injectors. In this type of injector, fuel presses onto the needle from two sides - top and bottom, where the fuel chambers are located. Both chambers are connected to each other, so the fuel pressure in them is equal and the needle closes the nozzle. However, the upper chamber (it is called the control chamber) is connected to the drain line through an electromagnetic valve, and fuel from the inlet line enters this chamber through a channel with a restriction - a throttle.
The operating principle of an electrohydraulic injector is as follows. When the valve is closed, the needle is pressed against the seat and closes the nozzle. When a pulse is applied to the valve, it opens, fuel from the control chamber enters the drain line and the pressure in the chamber drops sharply - at this moment the needle, on which the fuel now presses only from below, opens and injection occurs. When the injector opens, the control chamber remains connected to the intake manifold, but the intake throttle prevents fuel from quickly filling this chamber.
The electrohydraulic injector is widely used in diesel engines, including common rail fuel injection systems. These simple and reliable devices ensure long-term and high-quality engine operation.
Piezoelectric injectors are the most modern and reliable solution, which today is increasingly used on diesel engines with a common rail injection system. In general, the principle of operation of this nozzle repeats the principle inherent in electrohydraulic type nozzles, but in it the valve that opens the path for fuel from the upper chamber to the drain line is activated by a piezoelectric crystal.
As is known, a piezoelectric effect is observed in a number of crystals - under the influence of an external force they are deformed with the formation of an electric charge. Such crystals are also subject to the opposite effect - under the influence of electricity they are deformed, changing their size. Piezoelectric injectors use crystals that, when voltage is applied, increase their length and push the piston of the valve that releases fuel from the upper chamber into the drain line.
The big advantage of piezoelectric injectors is their speed. Changing the length of the crystal and opening the valve in them occurs on average 4 times faster than the opening of an electromagnetic type valve. This paved the way for the implementation of multiple injections in one stroke, which improves engine performance. In modern diesel engines, injection can be performed up to nine times per stroke.
An automobile injector is a device that is responsible for directly spraying fuel inside the combustion chamber. And not only the power of the car, but also fuel consumption depends on how its design is arranged and the coherence of each mechanism.
Essentially, this is a miniature pump with the help of which fuel (fuel mixture) reaches its final destination, where it is converted into energy. At the initial stage, you now understand what an injector is in a car and what functions it performs. Let's move forward.
Today, these devices come in various modifications, each of which has its own advantages. Specifically, these are mechanical, electromagnetic injectors, followed by piezoelectric, as well as electrohydraulic.
Basic information about the injector
The design features of the injectors are determined by their main task - precise, constant dosing of the required amount of fuel supplied to the combustion chamber. The pressure created in the injector is directly dependent on the type of fuel that passes through it. It can be at a level of 200 MPa, while remaining for a short period of time (which is about 1-2 milliseconds).
Not all injectors have a standardized appearance. They differ from each other in shape, spray method, size of spray elements, and process control procedure. Here it is important to note the difference in injection systems used for various types and types of equipment. The most common nozzles are pin nozzles, used in conjunction with the prechamber ignition system, as well as perforated nozzles, typical for engines running on diesel fuel.
It is important to note that the internal mechanism also directly depends on the method of controlling the injectors. They can be single spring, or double spring using special control sensors.
In addition to atomizing fuel, the injector must provide a seal to the combustion chamber so that the engine does not lose power during operation. To achieve this, modern developers are introducing various tricks and rational proposals, with the help of which two or more degrees of fuel pumping are introduced. But general fuel control is carried out using a special control unit that controls the fuel supply solenoid valves.
Now, a little more specific data about the real benefits of injectors and their role in ensuring the operation of the car. First of all, this device is the main connecting element between the engine and the fuel pump. Their purpose can be described as follows:
— ensure the correct dosage of fuel supplied to the engine;
— ensure the correct flow (angle, pressure, quantity) of the mixture, as well as its preparation;
— intermediary actions between the general formation and injection system and the combustion chamber;
— maintaining the correct release rate curve.
The design features of the injectors directly depend on the specific modification and control method (mixture supply). But piezoelectric injectors are considered the most effective, rational and practical today. Their advantage is the possibility of multiple injections in one cycle, as well as the speed of response.
The most common problems that cause contamination of the fuel supply device and subsequently the car begins to “act up” is the occurrence of deposits on the walls of the injectors, which are formed due to the use of low-quality fuel or with various impurities. All this can cause interruptions in operation, increased fuel consumption, and causeless loss of power.
To avoid this, it is necessary to periodically flush the fuel injectors.
Determining the beginning of problems is quite simple. They can be seen by the following basic characteristics:
— during the engine starting process, unplanned failures begin;
— the amount of fuel consumed has become significantly higher than the nominal (normal) consumption;
— exhausts began to have an uncharacteristic black color;
— engine operation is marked by tripling (doubling);
- when the engine is idling, there are frequent failures of its functioning in a rhythmic and uninterrupted mode.
As a rule, in this case it is not particularly difficult to solve the problem. To do this, you just need to rinse, clean and install the nozzle in its original position. It is important here to remove all contaminants that caused the failure.
You can do this:
- using a special liquid yourself by hand;
— ultrasonic cleaning;
— by adding special cleaning additives to the fuel (without disassembling the engine);
- on a special stand, using a special cleaning liquid.
The choice of cleaning method directly depends on the degree of contamination of the device and the problems that arise when starting the engine. What is important here is the time when you “came to your senses” and decided to fix the problem. The earlier it is, the less time-consuming and costly a cleaning method can be selected.
In practice, cleaning with additives or at home manually is most often used. These are the cheapest and easiest cleaning methods. If the car goes to a special service, then they can use cleaning at a stand, or with ultrasound. The last cleaning method is considered the most severe and is advisable in cases where the nozzle has very strong contamination that cannot be washed with ordinary liquid.
Nowadays, almost any gasoline engine in a passenger car uses an injection power system, which has replaced it. Due to a number of performance characteristics, the injector is superior to the carburetor system, so it is more in demand.
A little history
Such a power system has been actively installed on cars since the mid-80s, when environmental emission standards began to be introduced. The very idea of a fuel injection system appeared much earlier, back in the 30s. But then the main task was not in environmentally friendly exhaust, but in increasing power.
The first injection systems were used in combat aviation. At that time, it was a completely mechanical design that performed its functions quite well. With the advent of jet engines, injectors practically ceased to be used in military aircraft. On cars, the mechanical injector was not particularly widespread, since it could not fully perform its assigned functions. The fact is that the engine modes of a car change much more often than those of an airplane, and the mechanical system did not have time to adapt to the operation of the engine in a timely manner. In this regard, the carburetor won.
But the active development of electronics gave a “second life” to the injection system. And the struggle to reduce emissions of harmful substances played an important role in this. In search of a replacement for the carburetor, which no longer met environmental standards, the designers returned to the fuel injection system, but radically revised its operation and design.
What is an injector and why is it good?
The injector is literally translated as “injection”, so its second name is an injection system using a special nozzle. If in a carburetor fuel was mixed with air due to the vacuum created in the engine cylinders, then in an injection engine gasoline is supplied forcibly. This is the most fundamental difference between a carburetor and an injector.
The advantages of an injection engine, relative to carburetor engines, are:
- Economical consumption;
- Better power output;
- Less amount of harmful substances in exhaust gases;
- Easy to start the engine under any conditions.
And all this was achieved thanks to the fact that gasoline is supplied in portions, in accordance with the operating mode of the engine. Because of this feature, the air-fuel mixture enters the engine cylinders in optimal proportions. As a result, in almost all operating modes of the power plant, the maximum possible combustion of fuel occurs in the cylinders with a lower content of harmful substances and increased power output.
Video: The principle of operation of the injection engine power system
Types of injectors
The first injectors that began to be widely used on gasoline engines were still mechanical, but some electronic elements had already begun to appear that contributed to better engine performance.
A modern injection system includes a large number of electronic elements, and the entire operation of the system is controlled by a controller, aka.
There are three types of injection systems, differing in the type of fuel supply:
- Central;
- Distributed;
- Direct.
1. Central
The central injection system is now obsolete. Its essence is that fuel is injected in one place - at the entrance to the intake manifold, where it is mixed with air and distributed among the cylinders. In this case, its operation is very similar to a carburetor, with the only difference being that the fuel is supplied under pressure. This ensures its atomization and better mixing with air. But a number of factors could affect the uniform filling of the cylinders.
The central system was distinguished by its simplicity of design and quick response to changes in the operating parameters of the power plant. But it could not fully perform its functions. Due to the difference in filling the cylinders, it was not possible to achieve the required combustion of fuel in the cylinders.
2. Distributed
Multiport fuel injection
The distributed system is currently the most optimal and is used on many cars. With this type of injection engine, fuel is supplied separately to each cylinder, although it is also injected into the intake manifold. To ensure separate supply, the elements that supply fuel are installed next to the cylinder head, and gasoline is supplied to the valve operating area.
Thanks to this design, it is possible to achieve compliance with the proportions of the air-fuel mixture to ensure the desired combustion. Cars with such a system are more economical, but at the same time the power output is greater, and they pollute the environment less.
Disadvantages of a distributed system include a more complex design and sensitivity to fuel quality.
3. Direct
Direct fuel injection system
The direct injection system is currently the most advanced. It differs in that the fuel is injected directly into the cylinders, where it is mixed with air. This system is very similar in operating principle to a diesel one. It allows you to further reduce gasoline consumption and provides greater power output, but it is complex in design and very demanding on the quality of gasoline.
Design and principle of operation of the injector
Since the distributed injection system is the most common, we will use its example to consider the design and operating principle of the injector.
Conventionally, this system can be divided into two parts - mechanical and electronic. The first can additionally be called executive, since it ensures the supply of air-fuel mixture components to the cylinders. The electronic part provides control and management of the system.
Mechanical component of the injector
Power supply system for VAZ 2108, 2109, 21099 cars
The mechanical part of the injector includes:
- fuel tank;
- electric;
- gasoline purification filter;
- high pressure fuel lines;
- fuel rail;
- nozzles;
- throttle assembly;
Of course, this is not a complete list of components. The system may include additional elements that perform certain functions, it all depends on the design of the power unit and the power system. But these elements are basic for any engine with a distributed injection injector.
Video: Injector
Operating principle of the injector
As for the purpose of each of them, everything is simple. The tank is a container for gasoline where it is stored and supplied to the system. The electric fuel pump is located in the tank, that is, fuel is taken directly by it, and this element ensures the supply of fuel under pressure.
To prevent excess pressure, the system includes a pressure regulator. From the filter, through the fuel lines, gasoline moves to the fuel rail connected to all the injectors. The injectors themselves are installed in the intake manifold, not far from the cylinder valve assemblies.
Previously, injectors were completely mechanical, and they were triggered by fuel pressure. When a certain pressure value was reached, the fuel, overcoming the force of the injector spring, opened the supply valve and was injected through the nozzle.
A modern nozzle is electromagnetic. It is based on a conventional solenoid, that is, a wire winding and an armature. When an electrical pulse is supplied from the ECU, a magnetic field is formed in the winding, affecting the core, causing it to move, overcoming the force of the spring, and opening the feed channel. And since gasoline is supplied to the nozzle under pressure, gasoline enters the manifold through the opened channel and atomizer.
On the other hand, air is sucked into the system through the air filter. A throttle assembly with a damper is installed in the pipe through which the air moves. It is this valve that the driver acts upon by pressing the accelerator pedal. At the same time, it simply regulates the amount of air supplied to the cylinders, but the driver has no influence at all on the fuel dosage.
Electronic component
The main element of the electronic part of the fuel injection system is the electronic unit, consisting of a controller and a memory unit. The design also includes a large number of sensors, based on the readings of which the ECU controls the system.
For its operation, the ECU uses sensor readings:
- . This is a sensor that detects the remaining unburned air in the exhaust gases. Based on the lambda probe readings, the ECU evaluates whether the mixture is formed in the required proportions. Installed in the exhaust system of the car.
- Mass air flow sensor (abbr. MAF). This sensor determines the amount of air passing through the throttle assembly when it is sucked into the cylinders. Located in the air filter element housing;
- (abbr. DPDZ). This sensor provides a signal about the position of the accelerator pedal. Installed in the throttle assembly;
- Power plant temperature sensor. Based on the readings of this element, the mixture composition is adjusted depending on the engine temperature. Located near the thermostat;
- (abbr. DPKV). Based on the readings of this sensor, the cylinder into which a portion of fuel must be supplied, the time of gasoline supply, and sparking are determined. Installed near the crankshaft pulley;
- . Necessary for identifying the formation of detonation combustion and taking measures to eliminate it. Located on the cylinder block;
- Speed sensor. It is needed to create impulses from which the speed of the car is calculated. Based on its readings, the fuel mixture is adjusted. Mounted on the gearbox;
- Phase sensor. It is designed to determine the angular position of the camshaft. May not be available on some vehicles. If this sensor is present in the engine, phased injection is performed, that is, the opening impulse is received only for a specific injector. If this sensor is not present, then the injectors operate in pair mode, when the opening signal is sent to two injectors at once. Installed in the block head;
Now briefly about how everything works. The electric fuel pump fills the entire system with fuel. The controller receives readings from all sensors and compares them with the data stored in the memory unit. If the readings do not match, it adjusts the operation of the engine power system so as to achieve maximum agreement between the received data and those stored in the memory unit.
As for the fuel supply, based on data from the sensors, the controller calculates the opening time of the injectors in order to ensure the optimal amount of gasoline supplied to create the air-fuel mixture in the required proportion.
If one of the sensors breaks down, the controller goes into emergency mode. That is, it takes the average value of the readings of the faulty sensor and uses them for operation. In this case, the functioning of the motor may change - consumption increases, power decreases, and interruptions occur. But this does not apply to the DPKV; if it breaks down, the engine cannot function.
