The 411 on the Forms of Fuel Injection

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A fuel injection system. Image by CZMarlin/Wikimedia Commons/Public Domain.

A fuel injection system. Image by CZMarlin/Wikimedia Commons/Public Domain.

Almost every car on the road these days utilizes fuel injection, a manner of delivering fuel to engines to make them run. There are several types, each with their own features, and it’s a seemingly innocuous but vastly important part of what makes cars go.

Fuel injection caused the industry to pull the carb over

It wasn’t all that long ago that more cars employed carburetors, though fuel injection has been around for quite some time. Carburetors, or carbs as many call them, are simpler machines than fuel injection systems, though less efficient and worse regarding emissions.

How carburetors work is fairly simple, though this is majorly simplified: a carburetor draws air and fuel through separate inputs, with a butterfly valve in between. The valve opens and shuts at a mechanically set interval, which draws the fuel in to mix with the air. The carburetor, atop the intake manifold, sends the fuel/air mix to the engine.

The drawback is that less fuel makes it to ignition than with fuel injection in most cases, unless a person does a significant amount of tuning to reach peak efficiency.

It sounds like what it is

Fuel injection, which was actually developed for airplanes, is exactly what it sounds like: pressurized fuel gets injected (more like sprayed on a small scale) into the engine. Until electronically controlled (meaning computerized – called EFI) fuel injection was devised, it was mechanically controlled. Basically, nozzles are positioned at strategic points to spray fuel where it’s supposed to go along with the air coming in, which get compressed by the cylinders and detonated by the spark plugs.

There are a number of types, with direct injection and port injection being most common.

Direct injection uses a nozzle to aspirate fuel with air directly at the point of combustion, namely at the cylinder head, employing a series of injectors bolted to the top of the engine and manifold. Port injection positions the injectors close to the intake ports where the cylinders draw in air. Fuel is injected while air gets drawn in, which goes to the cylinder and so on.

For a time, many automakers used continuous injection, which supplied a controlled continuous feed of fuel.

Why they use it

Fuel injection systems put more fuel into engine relative to carburetors, meaning less is wasted and fuel economy is improved. It also more reliable and performs better in cold weather. Performance is also improved, which is why a lot of race cars (though curiously not NASCAR until a few years ago) employ injection and have done for decades.

Want to learn more?

Check out these links:

Wikipedia, the great Fountain of All Internet Knowledge

HowStuffWorks

Jalopnik

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