Vehicle fuel system

No car with an internal combustion engine under the hood will drive if its fuel tank is empty. But not only is the fuel in this tank. It still needs to be delivered to the cylinders. For this, the engine fuel system has been created. Let's consider what functions it has, how the vehicle of a gasoline unit differs from the version with which a diesel engine works. Let's also see what modern developments exist that increase the efficiency of supplying and mixing fuel with air.

What is the engine fuel system

The fuel system is the equipment that allows the engine to operate autonomously due to the combustion of the air-fuel mixture compressed in the cylinders. Depending on the car model, engine type and other factors, one fuel system can be very different from another, but they all have the same principle of operation: they supply fuel to the corresponding units, mix it with air and ensure uninterrupted supply of the mixture to the cylinders.

The fuel supply system itself does not provide autonomous operation of the power unit, regardless of its type. It is necessarily synchronized with the ignition system. The car can be equipped with one of several modifications that ensure the timely ignition of the VTS. Details about the varieties and the principle of operation of the SZ in the car are described in another review... The system also works in conjunction with the intake system of the internal combustion engine, which is described in detail. here.

True, the aforementioned work of the vehicle concerns gasoline units. The diesel engine works in a different way. In short, it doesn't have an ignition system. Diesel fuel ignites in the cylinder due to the hot air due to high compression. When the piston completes its compression stroke, the portion of air in the cylinder becomes very hot. At this moment, diesel fuel is injected, and the BTC lights up.

Purpose of the fuel system

Any engine that burns VTS is equipped with a vehicle, the various elements of which provide the following actions in the car:

1. Provide storage of fuel in a separate tank;
2. It takes fuel from the fuel tank;
3. Cleaning the environment from foreign particles;
4. Fuel supply to the unit in which it mixes with air;
5. Spraying VTS into a working cylinder;
6. Fuel return in case of excess.

The vehicle is designed so that the combustible mixture is supplied to the working cylinder at the moment when the combustion of the VTS will be most effective, and the maximum efficiency will be removed from the motor. Since each mode of the engine requires a different moment and rate of fuel supply, engineers have developed systems that adapt to the speed of the engine and to its load.

Fuel system device

Most fuel delivery systems have a similar design. Basically, the classic scheme will consist of the following elements:

• Fuel tank or tank. It stores fuel. Modern cars get more than just a metal container to which the highway fits. It has a rather complex device with several components that ensure the most efficient storage of gasoline or diesel fuel. This system includes adsorber, filter, level sensor and in many models an auto pump.
• Fuel line. This is usually a flexible rubber hose that connects the fuel pump to other components in the system. In many machines, the piping is partly flexible and partly rigid (this part consists of metal pipes). The soft tube constitutes the low-pressure fuel line. In the metal part of the line, gasoline or diesel fuel has a lot of pressure. Also, an automobile fuel line can be conditionally divided into two circuits. The first is responsible for feeding the engine with a fresh portion of fuel, and is called supply. On the second circuit (return), the system will drain the excess gasoline / diesel fuel back into the gas tank. Moreover, such a design can be not only in modern vehicles, but also in those that have a carburetor type of VTS preparation.
• Gasoline pump. The purpose of this device is to ensure constant pumping of the working medium from the reservoir to the sprayers or to the chamber in which the VTS is prepared. Depending on what type of motor is installed in the car, this mechanism can be electrically or mechanically driven. The electric pump is controlled by an electronic control unit, and is an integral part of the ICE injection system (injection motor). A mechanical pump is used in older cars in which a carburetor is installed on the motor. Basically, a gasoline internal combustion engine is equipped with one fuel pump, but there are also modifications of injection vehicles with a booster pump (in versions that include a fuel rail). The diesel engine is equipped with two pumps, one is a high-pressure fuel pump. It creates high pressure in the line (the device and the principle of operation of the device are described in detail separately). The second pumps fuel, making the main supercharger easier to operate. Pumps that create high pressure in diesel engines are powered by a plunger pair (what this is, is described here).
• Fuel cleaner. Most fuel systems will have a minimum of two filters. The first provides a rough cleaning, and is installed in the gas tank. The second is designed for finer fuel purification. This part is installed in front of the inlet to the fuel rail, high pressure fuel pump or in front of the carburetor. These items are consumables and need to be replaced periodically.
• Diesel engines also use equipment to heat the diesel fuel before it enters the cylinder. Its presence is due to the fact that diesel fuel has a high viscosity at low temperatures, and it becomes more difficult for the pump to cope with its task, and in some cases it is not able to pump fuel into the line. But for such units, the presence of glow plugs is also relevant. Read about how they differ from spark plugs and why they are needed. separately.

Depending on the type of system, other equipment may also be included in its design, which provides a finer work of fuel supply.

How does a car's fuel system work?

Since there is a wide variety of vehicles, each of them has its own mode of operation. But the key principles are no different. When the driver turns the key in the ignition lock (if an injector is installed on the internal combustion engine), a faint hum is heard coming from the side of the gas tank. The petrol pump was activated. It builds up pressure in the pipeline. If the car is carbureted, then in the classic version the fuel pump is mechanical, and until the unit starts rotating, the supercharger will not work.

When the starter motor turns the flywheel disk, all motor systems are forced to start synchronously. As the pistons move in the cylinders, the intake valves of the cylinder head open. Due to the vacuum, the cylinder chamber begins to fill with air in the intake manifold. At this moment, gasoline is injected into the passing air stream. For this, a nozzle is used (about how this element works and works, read here).

When the timing valves close, a spark is applied to the compressed air / fuel mixture. This discharge ignites the BTS, during which a large amount of energy is released, which pushes the piston to bottom dead center. Identical processes take place in adjacent cylinders, and the motor starts to work autonomously.

This schematic principle of operation is typical for most modern cars. But other modifications of fuel systems can be used in the car. Let's consider what are their differences.

Types of injection systems

All injection systems can be roughly divided into two:

• A variety for gasoline internal combustion engines;
• Variety for diesel internal combustion engines.

But even in these categories, there are several types of vehicles that will inject fuel in their own way into the air going to the cylinder chambers. Here are the key differences between each vehicle type.

Fuel systems for gasoline engines

In the history of the automotive industry, gasoline engines (as the main units of motor vehicles) appeared before diesel engines. Since air is required in the cylinders to ignite gasoline (without oxygen, not a single substance will ignite), engineers have developed a mechanical unit in which gasoline is mixed with air under the influence of natural physical processes. It depends on how well this process is performed whether the fuel burns out completely or not.

Initially, a special unit was created for this, which was located as close as possible to the engine on the intake manifold. This is a carburetor. Over time, it became clear that the characteristics of this equipment directly depend on the geometric features of the intake tract and cylinders, therefore, such engines could not always provide an ideal balance between fuel consumption and high efficiency.

In the early 50s of the last century, an injection analogue appeared, which provided forced metered injection of fuel into the air flow passing through the manifold. Let's consider the differences between these two system modifications.

Carburetor fuel supply system

The carburetor engine is easy to distinguish from the injection engine. Above the cylinder head, there will be a flat "pan" that is part of the intake system, and there is an air filter in it. This element is mounted directly on the carburetor. A carburetor is a multi-chamber device. Some contain gasoline, while others are empty, that is, they function as air channels through which a fresh air stream enters the collector.

A throttle valve is installed in the carburetor. In fact, this is the only regulator in such an engine that determines the amount of air entering the cylinders. This element is connected through a flexible tube to the ignition distributor (for details about the distributor, read in another article) to correct the SPL due to vacuum. Classic cars used one device. On sports cars, one carburetor could be installed per cylinder (or one for two pots), which significantly increased the power of the internal combustion engine.

Fuel supply occurs due to the suction of small portions of gasoline when the air flow passes by the fuel jets (about their structure and purpose is described here). Gasoline is sucked into the stream, and due to a thin hole in the nozzle, the portion is distributed into small particles.

Further, this VTS flow enters the intake manifold tract in which a vacuum was formed due to the open intake valve and the piston moving down. The fuel pump in such a system is needed exclusively in order to pump gasoline into the corresponding cavity of the carburetor (fuel chamber). The peculiarity of this arrangement is that the fuel pump has a rigid coupling with the mechanisms of the power unit (it depends on the type of engine, but in many models it is driven by a camshaft).

So that the fuel chamber of the carburetor does not overflow and gasoline does not fall uncontrollably into adjacent cavities, some devices are equipped with a return line. It ensures that excess gas is drained back into the gas tank.

Fuel injection system (fuel injection system)

Mono injection has been developed as an alternative to the classic carburetor. This is a system with forced atomization of gasoline (the presence of a nozzle allows you to divide a portion of fuel into smaller particles). In fact, this is the same carburetor, only one injector is installed in the intake manifold instead of the previous device. It is already controlled by a microprocessor, which also controls the electronic ignition system (read about it in detail here).

In this design, the fuel pump is already electric, and it generates a high pressure, which can reach several bar (this characteristic depends on the injection device). Such a vehicle with the help of electronics can change the amount of flow entering the fresh air stream (change the composition of the VTS - make it depleted or enriched), due to which all injectors are much more economical than carburetor engines with an identical volume.

Subsequently, the injector evolved into other modifications that not only increase the efficiency of gasoline spraying, but are also able to adapt to different operating modes of the unit. Details about the types of injection systems are described in a separate article... Here are the main vehicles with forced atomization of gasoline:

1. Monoinjection. We have already briefly reviewed its features.
2. Distributed injection. In short, its difference from the previous modification is that not one, but several nozzles are used for spraying. They are already installed in separate pipes of the intake manifold. Their location depends on the type of motor. In modern power plants, sprayers are installed as close as possible to the opening inlet valves. The individual atomizing element minimizes the loss of gasoline during the operation of the intake system. The design of these types of vehicles has a fuel rail (an elongated small tank that acts as a reservoir in which gasoline is under pressure). This module allows the system to distribute fuel evenly across the injectors without vibration. In advanced motors, a more complex battery type of vehicle is used. This is a fuel rail, on which there is necessarily a valve that controls the pressure in the system so that it does not burst (the injection pump is able to create a pressure critical for pipelines, since the plunger pair works from a rigid connection to the power unit). How it works, read separately... Motors with multipoint injection are labeled MPI (multi-point injection is described in detail here)
3. Direct injection. This type belongs to multi-point gasoline spraying systems. Its peculiarity is that the injectors are not located in the intake manifold, but directly in the cylinder head. This arrangement allows automakers to equip the internal combustion engine with a system that turns off several cylinders depending on the load on the unit. Thanks to this, even a very large engine can demonstrate decent efficiency, of course, if the driver uses this system correctly.

The essence of the operation of injection motors remains unchanged. With the help of a pump, gasoline is taken from the tank. The same mechanism or injection pump creates the pressure necessary for effective atomization. Depending on the design of the intake system, at the right time, a small portion of fuel sprayed through the nozzle is supplied (a fuel fog is formed, due to which the BTC burns much more efficiently).

Most modern vehicles are equipped with a ramp and a pressure regulator. In this version, fluctuations in the supply of gasoline are reduced, and it is evenly distributed over the injectors. The operation of the entire system is controlled by an electronic control unit in accordance with the algorithms embedded in the microprocessor.

Diesel fuel systems

The fuel systems of diesel engines are exclusively direct injection. The reason lies in the principle of HTS ignition. In such a modification of motors, there is no ignition system as such. The design of the unit implies the compression of air in the cylinder to such an extent that it heats up to several hundred degrees. When the piston reaches top dead center, the fuel system sprays diesel fuel into the cylinder. Under the influence of high temperature, a mixture of air and diesel fuel ignites, releasing the energy necessary for the movement of the piston.

Another feature of diesel engines is that, in comparison with gasoline analogues, their compression is much higher, therefore, the fuel system must create an extremely high pressure of diesel fuel in the rail. For this, only a high-pressure fuel pump is used, which operates on the basis of a plunger pair. A malfunction of this element will prevent the motor from working.

The design of this vehicle will include two fuel pumps. One simply pumps up diesel fuel to the main one, and the main one creates the required pressure. The most effective device and action is the Common Rail fuel system. She is described in detail in another article.

Here is a short video about what kind of system it is:

Exploring Common Rail. Diesel injectors.

As you can see, modern cars are equipped with better and more efficient fuel systems. However, these developments have a significant drawback. Although they work quite reliably, in case of breakdowns, their repair is much more expensive than servicing carburetor counterparts.

Possibilities of modern fuel systems

Despite the difficulties with repairs and the high cost of individual components of modern fuel systems, automakers are forced to implement these developments in their models for several reasons.

1. Firstly, these vehicles are capable of providing decent fuel economy compared to carburetor ICEs of the same volume. At the same time, engine power is not sacrificed, but in most models, on the contrary, an increase in power characteristics is observed in comparison with less productive modifications, but with the same volumes.
2. Secondly, modern fuel systems make it possible to adjust fuel consumption to the load on the power unit.
3. Third, by reducing the amount of fuel burned, the vehicle is more likely to meet high environmental standards.
4. Fourthly, the use of electronics makes it possible not only to give commands to the actuators, but to control the whole processes taking place inside the power unit. Mechanical devices are also quite effective, because carburetor machines have not yet gone out of use, but they are not able to change the modes of fuel supply.

So, as we have seen, modern vehicles allow not only the car to drive, but also to use the full potential of every drop of fuel, giving the driver pleasure from the dynamic operation of the power unit.

In conclusion - a short video about the operation of different fuel systems:

What are the types of injection in a gasoline and diesel engine, how they differ and which injection is better

Questions and answers:

How does the fuel system work? Fuel tank (gas tank), fuel pump, fuel line (low or high pressure), sprayers (nozzles, and in older models a carburetor).

What is the fuel system in a car? This is a system that provides storage of the fuel supply, its cleaning and pumping from the gas tank to the engine for mixing with air.

What kind of fuel systems are there? Carburetor, mono injection (one nozzle according to the carburetor principle), distributed injection (injector). Distributed injection also includes direct injection.