Halderman: Gasoline direct injection (GDI) has been used in Europe for many years and has proven to be reliable. This type of system uses an engine-driven, high-pressure fuel pump to create up to 2,900 pounds per square inch of pressure, and the fuel injector is located in the combustion chamber instead of in the intake port. The pistons are unique and are designed for GDI systems, but the rest of the engine is about the same as conventional port fuel-injected engine design.
There are some issues related to noise and carbon deposits. Noise is an issue as the system can sound like noisy valves when the engine is running. This noise is controlled by the vehicle manufacturer by using insulated supports for the fuel rail that carries the fuel to the fuel injectors.
The fuel injectors create a clicking sound when each is opened by the engine computer. This clicking can be heard if the engine is running and the hood is open but should not be heard from inside the vehicle.
The carbon issue can occur and reduce performance. Carbon is a byproduct of combustion. Some gasoline direct injection (GDI) systems that use a slit-type injector do not seem to be affected by the carbon because any carbon buildup is blasted away by the high-pressure discharge through the slit.
Some systems, however, use many small holes and these holes can become clogged, reducing engine power. These carbon issues can be prevented by using a dispersant such as Techron added to the fuel tank every six months.
James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. E-mail Halderman at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.
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