Common Rail History

Over 100 years ago, two mechanical versions of fuel injection systems for diesel engines were conceived. One version generated the fuel injection pressure with a sharp pumping cam and has been named “jerk type system”. The other version stored the pressure in an accumulator which was integrated into the injector body. Subsequently, the injection was mechanically triggered. The first solution was adopted broadly, because the second version did not have any advantages in a mechanical arrangement. The „jerk type system” with sharp cam is partially still in use today.

With the upcoming of electronics in the sixties of the last century, the solution which accumulated the pressurized fuel got a second chance. Injectors with electromagnetic control were developed. The injection process could then be actuated flexibly with an electronic control unit. The pressure was generated with a high pressure pump for all injectors. The pressurized fuel was brought to the injectors in a “Common Rail”. This flexibility to optimize the injection of diesel paved the way for the Common Rail technology.

The production start of the Common Rail system was in 1997 for both passenger car and marine diesel engines. In the truck engine sector, the breakthrough of Common Rail Injection took place in the first decade of the new millennium.

A technical revolution

The Common Rail injection revolutionized the diesel engine. Specific power outputs of over 100 horsepower per liter displacement and torque values of 200 newton-meters per liter have been achieved in passenger cars. All of this in connection with remarkably low fuel consumption and with exhaust emissions values which have not been considered to be possible a few years earlier.

In the meantime, Common Rail systems have entirely replaced the inline- and distributor- as well as the unit injector systems in the passenger car and truck domains. The share of diesel passenger car engines has increased exponentially since then. In the field of large diesel engines for diesel-electric locomotives, ships, heavy earthmoving machinery and for power generation, the vast implementation of the Common Rail injection system is going to take place during this decade.