Fuel Injection System and Types

Fuel injectors are tiny nozzles that are electronically controlled and used to atomise fuel under high pressure into the combustion chamber of an engine. It has valves that can open and close multiple times each second for operation. Most importantly, this fuel injection system became popular for its advantages over the carburettor.

Primarily, there are 4 types of fuel injection systems. Details about those are provided below:

1. Single Point Injection System

One kind of injection system that makes use of an injector is the single-point injection system. In this case, an engine has only one injector despite having four cylinders.

When automobile engines with injection systems were first discovered, this system was among them. At that time, an injector  replaced a jet carburettor, which was then mounted on the throttle body.

The outcome of this is identical to that of a carburettor system. As a result of this, it is possible to spray fuel into the throttle body compartment, but it comes from an injector rather than the carburettor jet.

Also, because the ECU has already calculated the volume of gasoline, it is unquestionably a superior version to its carburettor kind and is more accurate too.

Nevertheless, because only one injector was being used, there was a little disruption in the engine's performance at high RPM or  Revolution Per Minute.

2. Multi Point Fuel Injection

Compared to single-point fuel injection, this multi-point fuel injection (MPFI) is a more popular approach. The fundamental difference between this kind and the first type is that the number of injectors is now matched to the count of cylinders.

In other words, this is an engine with four cylinders and four injectors.

This scheme for multi-point injectors is equivalent to that for single-point injectors. However, the actuator is added more in this form.

Because each injector is located inside an intake manifold, fuel is delivered to the engine more efficiently with multi-point injectors (in front of the inlet valve).

However, this kind has a drawback in that it only functions as a single point at a time. In other words, all injectors will spray fuel simultaneously. Even if a single cylinder is in the combustion phase, this will keep the fuel spraying. As a result, fuel is used inefficiently.

Above all, this kind is undoubtedly superior to the single-point type for performance issues.

3. Sequential Fuel Injection

This is one of the prevalent fuel injection methods used in modern vehicles.

Although this type already has individual injection, the sequential fuel injection mechanism is fundamentally identical to MPFI. In other words, each injector functions independently in accordance with the movements of each piston rather than collectively.

For instance, only injector 1 operates in a four-cylinder engine when cylinder 1 is in the suction step, while all other injectors are at a standstill. This indicates that each injector operates alternately in accordance with each cylinder's schedule.

Though the scheme controller is quite different, this method is equivalent to MPFI. Additionally, because a sequential kind uses timing indicators for each cylinder, its controller architecture is more complicated. But its sequential variant performs better and uses fuel more efficiently than the MPFI.

4. Direct Injection System

A direct injection system is a type of fuel injection system mechanism that inserts the injector right into a cylinder. Then, this injector will spray fuel straight into the cylinder so that it resembles a diesel engine.

Because its previous kind sprayed fuel into the intake, there is a possibility for fuel to condense on the intake. Hence one of its key advantages is fuel economy. Also, this DI system is more economical because all of the fuel is put into the cylinder.

From a performance standpoint, it is comparable to MPFI, even though this system may perform better depending on the amount of gasoline released.

This fuel injection system is new, and its earlier DI systems were used with diesel engines. However, even though the DI system can now be used with petrol engines, fuel still only exits an engine during the suction step.

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Differences Between Carburettor and Fuel Injection

A vehicle's fuel injection system takes care of ensuring that its engine receives the right amount of fuel. Nevertheless, a fuel system functions as follows:

• Fuel is first taken from the fuel tank by a fuel pump, which then filters the fuel.
• This filter cleans the fuel to ensure it is free from debris. Also, it avoids clogging the carburettor, fuel lines, and the fuel injector.
• This filtered oil is delivered through the fuel lines to the fuel injector, and plastic or sturdy metal is used for building fuel lines. Furthermore, under the car's floor, these lines are visible, and they seem to be in areas at risk. So, they are put in a place where they won't be harmed by road conditions, weather, engine exhaust, or other auto elements.
• Depending on how the engine is built, the fuel injector operates differently. With a diesel engine, fuel is directly injected into the combustion chamber by the fuel injector. But, for a SI engine, the injector first injects oil into the carburettor, which then creates an air-fuel mixture before sending it to the combustion chamber.
• A pressure regulator manages the fuel pressure in the fuel injector.
• When fuel enters, the carburettor draws air from its surrounding area and combines it with the fuel to create an air-fuel mixture. According to the engine's needs, this air-fuel mixture is created and delivered to the combustion chamber.
• This air-fuel mixture is then compressed in the combustion chamber, which also ignites it and produces mechanical power.

Some basic functions of a fuel injector in an internal combustion engine are –

• One of the main functions of this fuel injection system in diesel engines is to help supply fuel to the cylinders. This component also has a significant impact on the design of an engine.
• It improves an engine's noise and performance characteristics.
• The fuel is delivered under incredibly high injection pressures.
• Fuel is atomised by the fuel injector into incredibly tiny fuel particles, guaranteeing that every tiny drop of fuel evaporates and undergoes combustion.
• Because of the engine's operation, its materials are made to endure increased strains for longevity.
• The injection system also ensures that gasoline is injected at the appropriate moment. In other words, injection timing is managed.
• Lastly, a proper amount of gasoline must be given to meet an engine's power requirements. Hence, injection metering is managed for this reason.

Low-pressure and high-pressure sides make up the two main sections of the fuel injection system.

• Low-pressure Components
  • Fuel filter
  • Oil tank
  • Fuel supply pump
• High-pressure Components
  • High-pressure pump
  • Accumulator
  • Fuel injector nozzle
  • Fuel injector

A few of the most prominent advantages of a fuel injection system include:

• The fuel injection system has enhanced the ratio of the volume of the fluid.
• Combustion has no effects on the supply of high-quality fuel when the compression ratio is increased.
• There is a reduction in fuel usage.
• Single or multi-point injection systems are better suited for supercharged engines.
• Nozzles make it simple to control the amount of fuel being used.
• This injection mechanism increases the engine's output.

Apart from the advantages, there are some disadvantages too of this system. A few of them are as follows:

• Carefully filtering the fuel is necessary to prevent harm.
• Every cylinder has an additional requirement for the nozzle.
• It might be comparatively more expensive.
• This system might demand greater attention.
• It can generate more sound.
• Construction is challenging.
• It might also lead to wearing.