Fuel Systems: Intake & Exhaust: Intake & exhaust systems

       

Electronic fuel injection systems

Summary
Electronic fuel injection is controlled by an electronic control unit. It has replaced the carburetor on most modern engines. EFI engines run more smoothly, with lower fuel consumption and emissions, and more power than carbureted engines.

The intake system is part of the fuel system. Its main function on a gasoline engine is to deliver the required amount of air-fuel mixture. Air is filtered by passing through an air cleaner.
Information from many parts of the engine are fed into an electronic control unit, which then determines how much fuel should be injected for those exact conditions.
Pressure from an electric pump supplies fuel to electrically controlled injectors.
There are two basic electronic fuel injection systems. - single-point, and multi-point.
In the single-point system, the intake manifold carries an air-fuel mixture. Fuel is sprayed into the top-centre of the intake manifold. This manifold is the same as on a carbureted system.
In a multi-point system, the intake manifold carries air only. Multi-point injection has a fuel injector in each inlet port going to each cylinder. Gasoline is sprayed into each port, toward each intake valve.
The intake system can be crucial in increasing engine output. This can be done by increasing volumetric efficiency, that is, by increasing the amount of air-fuel mixture burned in the cylinders.
In fuel injection systems, this partly occurs automatically because of the increased efficiency of fuel injection compared to carbureted systems. Output can also be improved by using large, free-flowing intake manifolds, and by using larger valves to admit more charge into the combustion chamber.
Another method uses forced induction or supercharging.