Fuel injection is a system for mixing fuel with air in an internal combustion engine. It has almost completely replaced carburetors and emerged as the primary system used in automotive engines in the past couple of decades.

The major functional difference between carburetors and fuel injection is that a fuel injection splits the fuel in groups by pumping it forcibly through a small nozzle under high pressure, while a carburetor depends on low pressure created by the air rushing in to add the fuel to the airstream.

A fuel injection is designed specifically for the type of fuel it handles like gasoline, Autogas, ethanol, methanol, and diesel. Most of the fuel injection systems are designed for gasoline or diesel applications. With the invention of electronic fuel injection, the diesel and gasoline hardware has become similar. A fuel injector comprises of only a nozzle and a valve. The power to inject the fuel comes from a pump or a pressure container.

Basic Function

The process of determining the quantity of fuel and it’s delivery to the engine are called as “fuel metering”. Fuel metering is the main function of any type of fuel injection. While early fuel injections used mechanical methods to determine fuel metering, the modern fuel injections use electronic methods. The fuel injector also acts as the fuel-dispensing nozzle and injects fuel directly into the air stream of the engine.

Objectives of a fuel Injection

Though the functional objectives for different types of fuel injections vary, the main task is supplying fuel to the combustion process. The objectives of a fuel injection are

• Fuel Efficiency
• Reliability
• Emission performance
• Output power
• To accommodate alternative fuels
• Smooth Operation
• Basic cost
• Maintenance cost
• Diagnostic Capability
• Environmental operation

It is practically impossible for a single system to have all these objectives as certain combinations are conflicting. But all the systems try to supply most of these objectives.

Benefits

Many benefits of fuel injection include

• Smoother and dependable engine response during quick transitions.
• Easier and faster engine starting.
• Better operation at a high or low ambient temperature.
• Increased fuel efficiency and
• Increased maintenance intervals.

Modern electronic fuel injections help in maintaining accurate fuel metering and help in producing less air pollutants.

Advantages of fuel injections over carburetors

• A fuel injection system delivers a more accurate and equal quantity of fuel to each cylinder than carburetor does. This improves the cylinder-to-cylinder distribution.
• The accurate fuel metering helps in reducing the toxic combustion byproducts emitted.
• Fuel injection helps in emitting less air pollutants than a carbureted engine does and helps in reducing pollution.
• A fuel injected engine produces more power than an equivalent carbureted engine.
• Fuel injection improves fuel efficiency of the engine. Because of the cylinder to cylinder fuel distribution, less fuel is required for the same output.

Different types of Fuel Injections

• Throttle-body injection: Commonly known as TBI, this system injects fuel at the throttle body.
• Continuous injection: In this system, the fuel sprays continuously from injector rather than getting pulsed every time a stroke is given to the engine.
• Multi-point fuel injection: In this system, the fuel is injected into the intake port along the side of cylinder’s intake valve rather than a central point.
• Central port injection: In this system, tubes along with valves are used to spray fuel at each intake rather than full throttle body.
• Direct Injection: It is the most used fuel injection. In this system, the nozzle used for injection is placed in the combustion chamber and the piston causes a depression when an initial combustion takes place.

Risks of Fuel Injection

Every system has it’s own share of benefits and risks. So does the fuel injection system, though the risks are very minimal. Due to the high pressure developed in the engine, a fuel injection system causes some potential hazards.

A residual pressure may remain in the engine even after the engine is turned off and it may cause an injury to the operator.

Because of the benefits and efficiency of fuel injections, they emerged as the majorly used systems in automotive engines.