Fuel injection

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Marvel Fuel Injection System Cross Section

Fuel injection is a system for introducing fuel into internal combustion engines, and into automotive engines, in particular. On petrol engines, fuel injection replaced carburetors from the 1980s onward. The primary difference between carburetion and fuel injection is that fuel injection atomizes the fuel through a small nozzle under high pressure, while a carburetor relies on suction created by intake air accelerated through a Venturi tube to draw the fuel into the airstream.

History

The concept of fuel injection has been around since the late 19th century, with inventors experimenting with various forms of injection in both diesel and petrol engines. However, it was not until the mid-20th century that fuel injection systems began to be widely used in automobiles. Early systems were mechanical, but electronic fuel injection (EFI), which offered better efficiency and control, started to replace mechanical systems in the 1970s.

Types of Fuel Injection Systems

There are several types of fuel injection systems, each with its own unique method of delivering fuel to the engine's combustion chamber.

Direct Injection

Direct injection (DI) injects fuel directly into the combustion chamber, bypassing the intake tract. This allows for better control of the fuel-air mixture, leading to improved efficiency and power. DI can be found in both petrol and diesel engines.

Port Injection

Port injection, also known as multi-point fuel injection (MPI), delivers fuel to the intake port just outside the cylinder. While not as efficient as direct injection, MPI is simpler and cheaper to manufacture and maintain.

Throttle Body Injection

Throttle body injection (TBI) is a type of fuel injection system where the injector delivers fuel into the throttle body, which is the entrance of the intake manifold. This system is simpler than port injection systems and was used extensively in the 1980s and early 1990s.

Advantages of Fuel Injection

Fuel injection systems offer several advantages over traditional carbureted systems, including:

• Improved fuel efficiency
• Increased power output
• Reduced emissions
• Better cold starting
• More precise fuel metering

Electronic Fuel Injection

Electronic fuel injection (EFI) systems use electronic controls to precisely meter the fuel delivery, often using a computer to monitor and adjust the fuel mixture in real time. EFI systems can be further divided into sequential, batched, or simultaneous injection, depending on how and when the fuel is injected.

Environmental Impact

Fuel injection systems have a positive impact on the environment by reducing vehicle emissions. By controlling the fuel-air mixture more precisely, EFI systems can reduce the amount of unburned hydrocarbons, carbon monoxide, and NOx (nitrogen oxides) released into the atmosphere.

Maintenance

While fuel injection systems are generally reliable, they do require regular maintenance to operate at peak efficiency. This includes cleaning the injectors, replacing the fuel filter, and ensuring the fuel pump is in good working order.

Future of Fuel Injection

The future of fuel injection lies in the development of more advanced systems that can further improve efficiency and reduce emissions. This includes innovations like variable injection timing, direct injection for petrol engines, and improvements in injector design.