Direct fuel injection is a fuel-delivery technology that allows gasoline engines to burn fuel more efficiently, resulting in more power, cleaner emissions, and increased fuel economy to meet today's evolving EPA standards.
How direct fuel injection works
Gasoline internal combustion engines work by sucking a mixture of gasoline and air into a cylinder, compressing it with a piston, and igniting it with a spark, the resulting explosion drives the piston downwards, producing the power. Traditional (indirect) fuel injection systems pre-mix the gasoline and air in a chamber just outside the cylinder in the intake manifold. In a direct-injection system, the air and gasoline are not pre-mixed, air comes in via the intake manifold, while the gasoline is injected directly into the cylinder.
Advantages of direct fuel injection
Combined with precise computer management, direct injection allows more accurate control over fuel metering (the amount of fuel injected) and injection timing (exactly when the fuel is introduced into the cylinder). The location of the injector also allows for a more optimal spray pattern that breaks the gasoline up into smaller droplets. The result provides a more complete combustion process -- in other words, more of the gasoline is burned, which translates to more power and less pollution.
Disadvantages of direct fuel injection
The primary disadvantages of direct injection engines are complexity and cost. Direct injection systems are more expensive to build because their components must be more rugged to include engine computer ECU management> The direct injection system also handle fuel at significantly higher pressures than indirect injection systems and the injectors themselves must be able to withstand the heat and pressure of combustion inside the cylinder.