EFI systems employ injectors to spray the fuel into the intake system. An electronic control unit processes data received from various sensors to optimize the air fuel mixture at any given moment by adjusting the amount of fuel injected.
EFI systems employ electronically controlled injectors to spray the fuel into the intake system.
There are two 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;
- a fuel pump to circulate fuel, and provide pressure in the system;
- a 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.