Bosch marketed its Common Rail System as a world’s first for passenger cars in 1997. Production of the Common Rail System for commercial vehicles started in 1999. The system takes its name from the shared pressure accumulator (“Common Rail”), which supplies all cylinders with fuel.

By contrast with other injection systems, pressure generation and injection are separate from each other in Common Rail technology. A separate high-pressure pump continuously feeds fuel into the rail. While other diesel direct-injection systems have to build up the high fuel pressure anew for each injection cycle, the Common Rail System permanently has at its disposal a fuel pressure matched to the operating conditions of the engine, even at low engine speeds.

In addition, Common Rail technology differs from conventional systems by providing multiple injections per working cycle. This cycle is divided into pre-injection (pilot injection) for quiet engine running, main injection for ideal power deployment and secondary injection for reduced emissions. The fuel reaches the injector via short pressure lines and then through the injection nozzles into the combustion chamber.

The higher the injection pressure, the finer the injection system vaporizes the fuel, thus permitting even more efficient combustion. In 2005, Bosch already introduced the third Common Rail generation with injection pressures of 1,800 bar for light commercial vehicles onto the market. A version of this system for medium-sized and heavy commercial vehicles will follow in 2007. The first Bosch generation for commercial vehicles went into series production in 1999 with an injection pressure of 1,400 bar. The second generation with a pressure of 1,600 bar followed in 2001.

Against the background of ever-stricter exhaust-gas pollutant values worldwide, Bosch has continued to further develop its injection systems. Based on the 1,800 bar injector, the company will continue to develop its systems for pressures of 2,000 bar and 2,200 bar.

The Common Rail System of the 4th generation for heavy commercial vehicles works with a newly developed injector with pressure converter. This compresses the fuel only when it reaches the injector to a maximum pressure of, at present, 2,100 bar. Its special feature: the pressure converter can be triggered independently of the injection nozzle. The freer design of the pressure process thus permitted minimizes the production of pollutants.