Direct injection (DI) combustion systems, which are the industry standard for diesels, appear to be the next generation of fuel injection for gasoline engines. The reasons for implementing this technology are legislative, and also include market requirements that drive the need to reduce fuel consumption, while at the same time, meet the increasingly stringent exhaust emissions regulations. According to engineers at Delphi Corp., gasoline direct injection can improve combustion efficiency and reduce pumping losses, both of which result in improved fuel economy.

The first-generation of this technology has been around since the early 1990s, and uses a wall-guided technology with side-mounted injectors to spray the gasoline directly into the cylinder at a pressure of up to 120 bar.

The in-cylinder charge motion (either swirl or tumble) helps to raise the charge up to the spark plug for ignition. Research by automotive engineers has determined that the side-mounted injector position presents the most feasible method for the vehicle manufacturers to utilize a direct injection system, since they would not have to redesign the cylinder head. Also, it's easier to cool the injector and spark plug using the side-mounted concept. However, with this design, fuel economy savings are only about 7%.