In 1893, Rudolf Diesel determined to prove his theory that a fuel could be made to burn by subjecting it to extreme pressure, without an ignition source. Furthermore, he demonstrated, the resulting energy could be transferred to a machine for the purpose of performing work. Diesel nearly killed himself perfecting his method, which is known as compression combustion. But it ultimately made him a millionaire [source: Energy Information Administration].
The diesel engine evolved in the 1920s to incorporate direct injection as a hallmark of its design. Diesels are built quite sturdily to survive the high stresses generated when they operate.
Gasoline, on the other hand, poses multiple challenges for anyone attempting to burn it in a direct injection application. For one thing, the injectors themselves must be able to withstand the extreme heat of the combustion chamber. And because of the different burn characteristics of gasoline, detonation was a problem. ("Detonation" is just another term for knocking, or multiple flame fronts colliding in a combustion chamber, which can cause serious harm to an engine.) Another problem that plagued GDI engineers was "coking," the build-up of cooked fuel deposits that fouled the injectors [source: Noyes, Wells].
Consequently, one of the biggest delays in getting GDI-equipped cars to the masses has been the fine-tuning research and development needed to make them as reliable as their standard counterparts. Automotive component suppliers including Bosch, Delphi, Denso and Siemens have come up with solutions: Rugged, high-pressure fuel injectors and the sophisticated electronics to make them perform optimally in GDI engines.
In the next section, we'll take a closer look at the pieces of a direct injection fuel system.