The fuel supply system is needed for the receipt of fuel from the gas tank, its further filtration, as well as the formation of an oxygen-fuel mixture with its transfer to the engine cylinders. There are currently several types of fuel systems. The most common in the 20th century was the carburetor, but today the injection system is becoming increasingly popular. There was also a third - single injection, which was only good because it allowed to slightly reduce fuel consumption. Let's take a closer look at the injection system and deal with its principle of operation.
General Provisions
Most modern engine fuel systems are similar. The difference can only be at the stage of mixture formation. The fuel system includes the following components:
- A fuel tank is a compact product that has a pump and a filter for cleaning from mechanical particles. The main purpose is fuel storage.
- Fuel lines form a complex of hose and tubes to move fuel from the tank to the mixture formation system.
- Mixing device. In our case, we are talking about an injector. This unit is designed to receive an emulsion (air-fuel mixture) and supply it to the cylinders in step with the engine.
- Mix control system control unit. It is installed only on injection engines, which is due to the need to control sensors, nozzles and valves.
- Fuel pump. In most cases, the immersion option is used. It is a small electric motor that connects to a liquid pump. Lubrication is carried out by fuel, and prolonged use of vehicles with less than 5 liters of fuel can lead to failure of the electric motor.
In short, an injector is a point feed of fuel through a nozzle. An electronic signal comes from the control unit. Despite the fact that the injector has a number of significant advantages over the carburetor, it has not been used for a long time. This was due to the technical complexity of the product, as well as the low maintainability of the parts that failed. Currently, point injection systems have almost replaced the carburetor. Let's take a closer look at why the injector is so good and what its features are.
Features of fuel equipment
The car has always been the object of attention of environmentalists. The exhaust gases are released directly into the atmosphere, which is fraught with its pollution. Diagnostics of the fuel system showed that the amount of emissions with improper mixture formation increases significantly. For this simple reason, it was decided to install a catalytic converter. However, this device showed good results only with a high-quality emulsion, and in the case of any deviations, its effectiveness dropped significantly. It was decided to replace the carburetor with a more accurate injection system, which was the injector. The first options included a large number of mechanical components and, according to research, such a system became worse and worse as the vehicle was used. This was quite natural, since important components and working bodies were polluted and damaged.
In order for the injection system to be able to correct itself, an electronic control unit (ECU) was created. Along with the mounted lambda probe, which is located in front of the catalytic converter, this gave good performance. We can confidently say that fuel prices are quite high today, and the injector is good just because it allows you to save gasoline or diesel. In addition, there are the following advantages:
- Increased engine performance. In particular, increased power by 5-10%.
- Improving the dynamic performance of the vehicle. The injector is more sensitive to changes in loads and adjusts the composition of the emulsion itself.
- An optimal air-fuel mixture reduces the amount and toxicity of exhaust gases.
- The injection system is easy to start regardless of weather conditions, which is a significant advantage over carburetor engines.
Fuel injection system and device
First of all, it is worth noting the fact that modern injection engines are equipped with nozzles, the number of which is equal to the number of cylinders. The nozzles are interconnected by a ramp. There the fuel is kept under slight pressure, and creates its electric device - a gasoline pump. The amount of fuel injected directly depends on the duration of the nozzle opening, which is determined by the control unit. For this, indicators are taken from various sensors that are installed throughout the vehicle. Now we will consider the main ones:
- Air flow sensor. It is used to determine the fullness of the cylinders with air. In the event of a breakdown, the readings are ignored, and tabular data are taken as the main indicators.
- The throttle position sensor reflects the load on the engine, which is due to the position of the throttle, cyclic air filling and engine speed.
- Refrigerant temperature sensor. Using this controller, electric fan control and correction of fuel supply and ignition are implemented. In the event of a malfunction, an instant diagnosis of the fuel system is optional. The temperature is taken depending on the duration of the internal combustion engine.
- The crankshaft position sensor (crankshaft) is needed to synchronize the system as a whole. The controller calculates not only the engine speed, but also its position at a certain point in time. Since it is a polar sensor, in the event of its malfunction, further operation of the vehicle is not possible.
- An oxygen sensor is needed to determine the% of oxygen in the gases emitted into the atmosphere. Information from this controller is transmitted to the computer, which, depending on the readings, corrects the emulsion.
It is worth paying attention to the fact that not all vehicles with an injector are equipped with an oxygen sensor. They are only those cars that are equipped with a catalytic converter with toxic standards "Euro-2" and "Euro-3."
Types of injection systems: single point injection
Currently, all systems are actively used. They are classified according to the number of nozzles and the place of fuel supply. There are three injection systems in total:
- single point (single injection);
- multipoint (distribution);
- direct.
First, let's look at single-point injection systems. They were created immediately after the carburetor and were considered more advanced, but nowadays they are gradually losing their popularity due to many reasons. There are several undeniable advantages of such systems. The main ones are significant fuel economy. Given that fuel prices are rather high today, such an injector is relevant. It is interesting that this system contains slightly less electronics, therefore it is more reliable and stable. When information from the sensors is transmitted to the control element, the injection parameters immediately change. It is very interesting that almost any carburetor engine can be converted to a single-point injection without significant structural changes. The main disadvantage of such systems is the low throttle response of the internal combustion engine, as well as the deposition of a significant amount of fuel on the walls of the manifold, although this problem was also inherent in carburetor models.
Since the nozzle in this case is only one, it is located on the intake manifold in place of the carburetor. Since the nozzle was in a good place and was constantly under a stream of cold air, its reliability was at the highest level, and the design was extremely simple. Flushing the fuel system with a single-point injection did not take much time, since it was enough to purge only one nozzle, but increased environmental requirements led to the development of other, more modern systems.
Multipoint Injection Systems
Distributed injection is considered more modern, sophisticated and less reliable. In this case, each cylinder is equipped with an insulated nozzle, which is located in the intake manifold in the immediate vicinity of the intake valve. Therefore, the supply of the emulsion is carried out separately. As noted above, with such an injection, the power of the internal combustion engine can be increased to 5-10%, which will be noticeable when driving on the road. Another interesting point: this fuel injection system is good in that the nozzle is very close to the intake valve. This minimizes the subsidence of fuel on the walls of the manifold, so that you can achieve significant fuel economy.
There are several types of multipoint injection:
- Simultaneous - all nozzles open at the same time.
- Pairwise-parallel - opening nozzles in pairs. One nozzle opens to the intake stroke, and the second before the exhaust stroke. Currently, such a system is used only at the time of emergency start of the internal combustion engine in the event of a phase failure ( crankshaft position sensor).
- Phased - each nozzle is controlled separately, and opens before the intake stroke.
In this case, the system is quite complex and relies entirely on the accuracy of the electronics. For example, flushing the fuel system will require much more time, as each nozzle needs to be flushed. Now let's move on and consider another popular type of injection.
Direct injection
Injection cars with such systems can be considered the most environmentally friendly. The main goal of introducing this injection method is to improve the quality of the fuel mixture and slightly increase the efficiency of the vehicle engine. The main advantages of this solution are as follows:
- thorough spraying of the emulsion;
- the formation of a high-quality mixture;
- effective use of emulsion at various stages of ICE operation.
Based on these advantages, we can say that such systems save fuel. This is especially noticeable with a quiet ride in urban conditions. If we compare two cars with the same engine capacity, but with different injection systems, for example, direct and multi-point, then the immediate system will noticeably better dynamic characteristics. The exhaust gases are less toxic, and the liter capacity taken will be slightly higher due to air cooling and the fact that the pressure in the fuel system is slightly increased.
But it is worth paying attention to the sensitivity of direct injection systems to fuel quality. If we take into account the standards of Russia and Ukraine, the sulfur content should not be higher than 500 mg per 1 liter of fuel. At the same time, European standards imply the content of this element is 150, 50 and even 10 mg per liter of gasoline or diesel.
If we briefly consider this system, then it looks as follows: nozzles are located in the cylinder head. Based on this, the injection is carried out directly into the cylinders. It is worth noting that this injection system is suitable for many gasoline engines. As noted above, high pressure is used in the fuel system, under which the emulsion is fed directly into the combustion chamber, bypassing the intake manifold.
Fuel Injection System: Poor Driving
A little higher, we examined the direct injection, which was first used on Mitsubishi cars, which had the abbreviation GDI. Let's briefly look at one of the main modes - work on lean mixture. Its essence is that the vehicle in this case operates at low loads and moderate speeds up to 120 kilometers per hour. Fuel injection is carried out by a torch in the final stage of compression. Reflecting from the piston, the fuel mixes with air and enters the zone of the spark plug. It turns out that in the chamber the mixture is significantly depleted, however, its charge in the vicinity of the spark plug can be considered optimal. This is enough to ignite it, after which the rest of the emulsion lights up. In fact, such a fuel injection system ensures the normal operation of the internal combustion engine even with an air / fuel ratio of 40: 1.
This is a very effective approach that allows you to significantly save fuel. But it is worth paying attention that the issue of neutralizing exhaust gases has become an acute issue. The fact is that the catalyst is inefficient, since nitric oxide is formed. In this case, exhaust gas recirculation is used. A special ERG system allows the emulsion to be diluted with exhaust gases. This somewhat reduces the combustion temperature and neutralizes the formation of oxides. However, this approach will not allow to increase the load on the engine. To partially solve the problem, a storage catalyst is used. The latter is extremely sensitive to high sulfur fuel. For this reason, a periodic check of the fuel system is required.
Homogeneous mixture formation and 2-stage mode
Power mode (homogeneous mixture formation) is an ideal solution for aggressive driving in urban conditions, overtaking, as well as driving on highways and highways. In this case, a conical torch is used, it is less economical compared to the previous version. The injection is carried out at the intake stroke, and the formed emulsion usually has a ratio of 14.7: 1, i.e. close to stoichiometric. In fact, this automatic fuel supply system is exactly the same as the distribution one.
The two-stage mode involves the injection of fuel at a compression stroke, as well as start-up. The main task is a sharp increase in the engine. A striking example of the effective operation of such a system is the movement at low speeds and a sharp click on the accelerator. In this case, the probability of detonation increases significantly. For this simple reason, instead of one stage, the injection takes place in two.
At the first stage, a small amount of fuel is injected at the intake stroke. This allows you to slightly lower the temperature of the air in the cylinder. We can say that in the cylinder there will be a super-poor mixture in a ratio of 60: 1, therefore, detonation is impossible as such. At the final stage of the compression stroke, a fuel jet is injected, which brings the emulsion to a rich one in a ratio of about 12: 1. Today we can say that such a fuel system of the engine was introduced only for vehicles of the European market. This is due to the fact that Japan does not have high speeds, therefore, there are no high engine loads. In Europe, a large number of freeways and autobahns, so drivers are used to driving fast, and this is a big load on the internal combustion engine.
Something else interesting
It is worth paying attention to the fact that, unlike carburetor systems, injection requires that there is a regular check of the fuel system. This is due to the fact that a large number of complex electronics can fail. As a result, this will lead to undesirable consequences. For example, excess air in the fuel system will lead to a violation of the composition of the emulsion and the wrong ratio of the mixture. In the future, this affects the engine, unstable operation appears, controllers fail, etc. In essence, an injector is a complex system that determines when a spark needs to be supplied to the cylinders, how to deliver a high-quality mixture to the cylinder block or intake manifold, when to open the nozzles and what ratio of air and gasoline should be in the emulsion. All of these factors affect the synchronized operation of the fuel system. It is interesting that without most controllers the machine can work properly, while there will be no significant deviations, since there are emergency records and tables that will be used.
The efficiency of the internal combustion engine in our case is determined by how correct the data received from the controllers will be. The more accurate they are, the less possible various malfunctions of the fuel system. An important role is played by the response speed of the system as a whole. Unlike carburetors, manual adjustment is not required here, and this eliminates errors during calibration work. Therefore, we get a more complete combustion of the mixture and a better system from an environmental point of view.
Conclusion
In conclusion, it is worth telling a little about the disadvantages that are inherent in injection systems. The main disadvantage is the high cost of ICE.By and large, the cost of such units will be approximately 15% higher, which is significant. But there are other disadvantages. For example, a failed valve in the fuel system in most cases cannot be repaired, which is due to a violation of the tightness, so it just needs to be changed. This also applies to maintainability of the equipment as a whole. Some components and parts are much easier to buy new than to spend money on their repair. This quality is not inherent in carburetor vehicles, where it is possible to sort through all the important components and restore their performance without a lot of time and effort. Without a doubt, the electronic fuel supply system is being repaired by large forces and means. Sophisticated electronics can hardly be restored to the first station.
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