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What is Fuel Injection?

Updated: Oct 22, 2019

How the modern engine gets it's fuel.

When the internal combustion engine first came into use, the fuel was supplied via the carburetor. This method used simple physics to create a vacuum which would atomize the fuel, allowing it to mix with the air.

Modern cars now use fuel injection to achieve this. Today we’ll talk about the basic principles surrounding fuel injection, and how it actually works.

In order for an engine to run smoothly and efficiently, it needs a healthy mixture of air and fuel. In order for the air and fuel to mix, the fuel must be atomised. This is the role of the fuel injector.

The fuel system in a modern car is comprised of the fuel tank, pump, pressure regulator, fuel rail, and the injectors.

The fuel is sent from the tank to the engine bay, usually at a pressure between 30-60 PSI, where it is fed into the fuel injectors.

They will then open, allowing the fuel to pass through and spray into the intake. One of the most important factors in this whole equation is the spray pattern of the injector.

Without a proper spray pattern, the fuel won’t mix as thoroughly with the air, and the engine won’t perform to its full potential. This is why it's so important to ensure you're injectors are clean.

The ideal spray pattern is usually quite similar to that of a spray bottle, where all of the liquid is atomised into a mist, and directed towards the target in a conical shape.

Fuel injection, unlike the carburettor, is not controlled by a vacuum. The injectors are plugged into the Engine Control Unit.

The ECU controls the timing and duration that the injectors are open. This is then tuned to ensure the optimum power and efficiency.

The idea is to have each injector fire individually, just fractions of a second before the intake valve opens. This facilitates proper mixture, as well as fuel efficiency.

The biggest advantage of fuel injection over the carburettor is that each cylinder is provided with the exact same amount of fuel, in the same fashion, every time. It is vastly more consistent and efficient than the carburettor.

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