Fuel Injectors And Their Various Types
A car’s engine is a very fascinating machine. It has thousands of parts that work together to help your car run in its most optimum and efficient manner. One such part is the fuel injector. A fuel injector, as its name suggests is a device that injects the fuel into the car’s cylinders.
However, it must be noted that the fuel injection system is a fairly new technology and has come quite recently. It is an electronically controlled unit that sends equal and optimum amounts of fuel into each of the cylinders. Previously this work was done by something called the carburetor. Even in the time that fuel injectors have come about, there have been numerous developments in the technology which has led to the development of different types of fuel injection systems.
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The Carburetors
Like a fuel injector system, the carburetors were connected to something called the fuel rail, which is, in simple terms, a pipe delivering fuel to the combustion chamber. At a very basic level, the carburetor is a device that mixes fuel and air in the optimum ratio before sending it to the cylinder or combustion chamber. The advantages of carburetors are that they are easy to maintain and do not require electricity to run. It uses the natural air suction of the engine to send the fuel into the combustion chamber.
Unfortunately, there is a major disadvantage of the Carburetor. Since there is only one device fixed in the engine, it supplies fuel to all the cylinders. As a result, the fuel distribution to the cylinders remains unequal. You could say that fitting twin carburetors to the engine would arrest the problem, and you would not be wrong but fitting twin carburetors is not easy as getting them to work in a timed fashion can get quite complicated. To solve this problem most modern cars are fitted with fuel injectors.
Fuel Injection System
To overcome the disadvantages of the carburetor system, fuel injection technology is the most common technology put in cars today. It is connected to the fuel rail which delivers fuel up to the injectors. Each cylinder is fitted with an injector which, thanks to an electronic device called the Engine Control Unit (ECU) ensures that a specific amount of fuel at specific time intervals is delivered within the cylinder or combustion chamber. These engines are usually more efficient and powerful than the carbureted engines. Another major difference between the carburetor and the fuel injection system is that the former relies on the suction power of the engine to draw the fuel in while the injector, well, injects or pushes the fuel into the combustion chamber as a result the car gets more power at lower speeds, smoother idling, and better response.
Over the course of time, there have been quite a few developments that have taken place in terms of the fuel injectors. In fact, there are 4 kinds of fuel injectors-
Throttle Body Injection (TBI)
This system is also known as single-point injection. In this case, a single injector is placed inside the throttle body where the fuel mixes with the air before being sent to the intake manifold. This system was one of the first forms of fuel injections seen in a car. However, as compared to what we get today, it has a few limitations in terms of precision and efficiency although it did have more precision and efficiency than a carburetor. This system was commonly seen in some cars like the 2005–2010 Ford Mustang or Chevrolet Camaro.
In a few ways, there is no denying that the TBI is quite similar to the carburetor in certain aspects like mixing air and fuel together and sending it to the intake manifold. Now, since the engine uses only one injector, the performance of the engine at higher RPMs is not the best and seems slightly uncomfortable.
Port/ Multipoint Fuel Injection (PFI/ MPFI)
Also known as an indirect injection system, one major difference between the PFI/MPFI engines to the TBI engine includes the number of fuel injectors. While TBI engines use a single fuel injector for all the cylinders combined, the PFI/MPFI engine uses one injector per cylinder. Moreover, in this system, the fuel is injected directly into the engine port rather than into the cylinder or the engine manifold. This means that the fuel is injected into a chamber right behind the intake valve.
The fuel is injected into the cylinder separately and individually through a different injector. Due to this, the PFI/MPFI engine provides better fuel efficiency and better performance than a TBI engine. The PFI/MPFI engines distribute the fuel more precisely and equally among all the cylinders. The PFI/MPFI engines are also of three types-
- Sequential: Also known as a timed injection, this system is designed to inject fuel into each cylinder in a specific order that is each injector works individually according to the steps of each of the pistons. These are the most precise forms of MPFI and were seen in cars like the 2010 Mazda RX-7, the 2010–2015 Toyota Supra, and the 2010–2016 Mitsubishi Lancer EVO.
- Batched: In this system, the fuel is injected into the cylinders in groups or batches, that is two or more injections release fuel into their respective cylinders together but not all the injectors of the engine will be working together. Although this system is simpler and less expensive than sequential systems but does not provide the same level of precision and efficiency. It is important to note that since the fuel is delivered in batches, the amount of fuel sent to each cylinder may differ a little and lead to issues with engine efficiency and more pollution.
- Simultaneous: in this system the fuel is injected into all the cylinders at the same time through their respective fuel injectors.
The MPFI engine has better efficiency and lesser carbon emission than the older systems. Moreover, this system also provides a smoother performance, especially during sudden acceleration and sudden braking.
Gasoline Direct Injection System (GDI)
Also known as a Direct injection system this system is very similar to a diesel engine. Instead of the fuel being injected into the intake valve, this method sees the fuel being injected directly into the cylinder. Typically the fuel will be injected in during the compression stroke of the engine. This results in better fuel and air mixture thereby giving out better engine efficiency and performance.
The fuel is sprayed into the cylinder or combustion chamber in a highly atomized mist allowing it to mix with the air in a much better ratio. When the fuel combusts, the pressure pushes the piston down which thereby causes the crankshaft to turn. With the fuel being sent directly into the combustion chamber, the mixture of fuel and air is much better controlled and it results in improved fuel efficiency and engine performance with a bonus of reduced emissions due to more effective burning of fuel. However, the GDI system can be more complex than the other systems and require more pressure to inject the fuel than the others. There are three types of GDI systems-
- The Spray-Guided System: In this system, the fuel injector is located on top of the cylinder or combustion chamber, right next to the spark plug. The fuel is sprayed into the chamber in a specific pattern to ensure an even distribution of fuel throughout the chamber
- The Wall-Guided System: In this system, the fuel injectors are placed on the wall of the combustion chamber in such a way that when the fuel is sprayed into the chamber in such a way that the fuel first touches the walls of the chamber before it comes in contact with the piston. Since the distance between the fuel and the spark plug is slightly greater, there is a swirl cavity on the piston that allows the fuel to bounce up toward the spark plug. This method typically required higher pressure than the previous one
- The Air-Guided System: Like in the previous system, the distance between the spark plug and fuel injector is quite high. The injector is located very close to the intake valve which helps the air and fuel to mix the moment the two of them enter the combustion chamber. The production of this system may be more expensive and complex than other types of fuel injection systems
Dual Injection System
As the name suggests, this system has two fuel injectors. The system incorporates two of the previously mentioned systems as it consists of a direct injection system and a port injection system. This system is found in the latest gasoline engines and it improves efficiency over the other types of engines.
The two injectors in this system are of two types. The direct injector placed near the spark plug is a high-pressure direct injector, and the second is placed in the chamber behind the intake valve which is a low-pressure port injector. At low RPMs, the system relies mostly on the port injector since it provides a better air-fuel mixture. However, when the RPM increases, the direct injector steps in, and the port injector stops to give way to the former. This increases efficiency since the direct injector is faster at higher RPMs. However, when the RPM goes even higher, the two injectors work together to ensure maximum performance which improves fuel efficiency while at the same time reducing emissions. The only drawback of this system is the increased number of parts and increased cost of production
In Conclusion
Fuel injectors are a very integral part of modern cars. Unlike the older systems where a carburetor was used, the fuel injectors are run by the electronically controlled ECU which ensures a smooth and equal delivery of fuel to each of the cylinders. As a result of these modern systems, even smaller engines tend to produce a lot more power as compared to older cars. Moreover, while this system produces more power, the fuel injection also ensures better combustion of fuel meaning better fuel consumption and lesser harmful emissions.
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