What is Fuel Injection
In trying to keep up with emission and fuel efficiency regulations, the fuel system used in cars has changed over the years, evolving from carburetor models to the modern multiport fuel injection system.
In fact, fuel injection systems do a better and more efficient job in providing fuel to your car engine when it is idling, cruising, or speeding down the highway, under different load and weather conditions. And with much lower harmful emissions. This is the main reason why all cars sold in the Unites States now come equipped with fuel injection.
You will find many specific variations on the injection systems in use, depending on vehicle and engine model; but under the hood of those cars you see speeding down roads and highways nowadays, you will find three main differences.
First, fuel injection systems may be divided in two broad categories: throttle body and multiport fuel injection system.
The throttle body system, the first fuel injection model to modify the carburetor, comes with one or two injector nozzles mounted on a throttle body assembly, which sits center top on the intake manifold. This type of arrangement is also called indirect injection system because the valve operating the fuel injector sprays gasoline into the center of the intake, away from the cylinders.
Many multiport fuel injection systems - which actually came to replace the carburetor - are considered indirect too. Aligned in a fuel rail, these injectors spray fuel just above the intake valves of each intake port. On a direct injection system - found in some gasoline engines and all diesel fuel injection engines - these same injectors spray fuel directly into the cylinder combustion chamber.
Both direct and indirect fuel injection systems result in a better air-fuel mixture control, lower harmful emissions and a higher power output to the engine than the first throttle body injection style.
Another difference you will find in fuel injection systems is in valve timing to "feed" gasoline to the intake manifold:
1. Timed injection method: in this system, the nozzles "squeeze" fuel just before or as the intake valve opens. This is the method used in diesel fuel injection.
2. Intermittent injection method: where injectors open and close to provide fuel regardless of the intake valve position.
On these two systems, the car's computer receives electrical signals from different sensors and other electronically controlled devices to operate the injector valves according to the engine needs. You will hear referred to this as Electronic Fuel Injection.
3. Continuous injection method: here, as its name implies, injectors spray fuel to the intake manifold without interruption. The amount of fuel they inject is controlled through fuel pressure.
The last general variation you will see in fuel injection systems is in their valve operation:
Depending on the engine model, these valves will be working simultaneously, opening and closing at the same time to provide fuel to the intake manifold; on other models, you will find injector valves that open and close in sequence, one at a time, in a constant cycle; or they may work in clusters - a group of injector valves opening and closing simultaneously, alternating with other group of valves that operate in unison as well.
Every car manufacturer has come up with its own version within these broad categories, but all these different fuel injection systems have the same purpose: provide you with a better and more efficient engine operation.
