Electronic fuel injection

EFI systems use electronically controlled injectors to spray the fuel. There are 2 basic systems - throttle-body injection, also called single-point injection. And multi-point injection.

Throttle-body injection sprays fuel into the air as it passes through to the intake manifold.

Multi-point injection has an injector for each cylinder, which sprays fuel directly into the intake valve port. The whole system has

• a fuel tank to store the fuel;
• fuel pump to circulate fuel, and provide pressure in the system;
• fuel filter to clean the fuel and protect the injectors;
• a fuel rail, or pipe, to supply the injectors with fuel;
• injectors which spray into the intake valve ports;
• a pressure regulator to control pressure in the system;
• a throttle-body, with a throttle valve to control the flow of air to the engine;
• an air cleaner, ducting and an airflow meter, to provide clean, measured air;
• and a plenum chamber, or surge chamber, to dampen the flow of air.

There is also an electronic control unit - a computer that receives data from sensors around the engine. It processes this data, and uses the results to operate the injectors.

Source: CDX Global