FUEL INJECTION SYSTEM: Objectives, Advantages & Disadvantages


Fuel injection system is used for introducing fuel into an internal combustion engine.

It replaced carburetors in the 1980s and 1990s and became the main fuel supply system for automobile engines.

Since the internal combustion engine was first used, there have been various injection systems.


The main difference between the carburetor and fuel injection is that fuel injection sprays fuel from a small nozzle under high pressure, whereas the carburetor depends on the intake air, which is accelerated through the Venturi tube to flow the fuel.

The latest fuel injection system is specially designed for the type of fuel used.

Some systems are designed for multiple fuel types (sensors are used to tune to the fuel currently in use).

Most fuel injection systems are designed for gasoline or diesel applications.


The performance of the diesel engine is greatly influenced by the design of the injection system.

Indeed, the most notable advances in diesel engines came directly from good fuel injection systems.

The main purpose of the system is to fuel the cylinders of a diesel engine, but the method of fueling makes all the differences in engine performance, emissions, and noise characteristics.

This means that the structure and materials of the system components should be selected to withstand higher loads in order to function for a long time to achieve the engine durability goal.

Higher manufacturing accuracy and tighter tolerances are required for the system to function efficiently.

All of these features mean that the cost of the system can be up to 30% of the total cost of the engine.

The main purpose of the fuel injection system is to fuel the cylinders of the engine.

To use this fuel effectively for the engine, do the following:

Fuel must be injected at the right time.

You need to control the injection volume.


Everyone shares a central role in fueling the combustion process, but how to optimize a particular system is a design decision.

There are several competing goals, including:

Power output.

Fuel Efficiency.

Emission Performance.

Ability to use alternative fuels.


Operability and smooth operation.

Initial cost.

Maintenance cost.

Diagnostic capability.

Environment range Operation.

Engine tuning.

An ideal fuel injection system can supply the right amount of fuel under all engine operating conditions.

This usually means accurate air-fuel ratio (lambda) control.

This allows, for example, easy engine operation even at low engine temperatures (cold start), proper adaptation to a wide altitude and ambient temperature range, precisely controlled engine speeds (idling and redline speeds), good fuel efficiency, and the lowest possible exhaust emissions (to allow emission control devices such as three-way catalytic converters to function properly).

In reality, there is no ideal fuel injection system, but there are many different fuel injection systems with specific strengths and weaknesses.

Most of these systems have been discontinued due to the common rail direct injection used in many passenger cars today (2021).

The common rail injection allows direct injection of gasoline, making it more suitable for direct injection of diesel fuel.

There are several factors to consider when designing a fuel injection system.

System cost.

Engine performance and vehicle handling (easy to start, smooth running, etc.)

Exhaust emissions.

Ease of diagnosis and service.

Fuel efficiency.


Functions that operate on different fuels.

All fuel injections system consists of three basic components:

There is at least one fuel injection device (sometimes called an injection device), a device that produces sufficient injection pressure, and a device that measures the correct amount.

These three basic components can be individual devices (injection valves, fuel distributors, fuel pumps), partially combined devices (injection valves and injection pumps), or fully combined devices (injection valves).

Early mechanical injection systems (other than airblast injection) typically use injectors (with needle nozzles) in combination with a single (or multiple) relatively sophisticated helical injection pumps to weigh fuel and generated the injection pressure.

These were suitable for all types of conventional direct injection and chamber injection systems, not just multipoint intermittent injection systems.

In modern engines, fuel weighing and injection valve activation are typically performed by the engine control unit.

Therefore, the fuel injection pump does not need to weigh the fuel or activate the injection valve. It only provides injection pressure.

These advanced systems are used in multipoint injection engines and common rail injection engines. Pump nozzle systems have been mass-produced in the past, but have proven to be inferior to common rail injection.


Improves performance.

Engines equipped with EFI provide higher power and torque than the carburetor version of the same engine.

Reduced fuel consumption and emissions.

Improved reliability Less maintenance and less downtime.

Boot has been improved.


It is important to carefully filter the fuel as it can cause damage.

It is a difficult to build.

The cost is high.

It required more maintenance.

It makes more sound.

May lead to wear.

Each cylinder has additional nozzle requirements.


The purpose of the fuel injection system is to fuel the engine cylinders with precise control over injection timing, fuel spray, and other parameters.

The main types of injector systems are unit injectors, unit injectors and common rails.

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