Summary
EFI is now the most common fuel system, the injectors spray fuel into the air/intake ports for combustion inside the engine.
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.
