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 utilized still 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 actuation were developed. The injection process can then be controlled flexibly with an electronic control unit. The pressure is generated with a high-pressure pump for all injectors. The pressurized fuel is 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 this 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 were impossible to achieve a few years earlier.

In the meantime, Common Rail systems have entirely replaced the jerk type systems in the passenger car and truck domains. 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 still ongoing.

The Common Rail technology is also a key when it comes to the use of renewable green fuels in the compression ignition, Diesel process engines, the process providing the highest thermodynamic efficiency. A new, CO2-, carbon-neutral aera of the internal combustion engines has begun.

The flexibility inherent to the electronically controlled Common Rail technology is fully available when using green fuels injection and will contribute to a future world free of pollutant and greenhouse depleting tailpipe emissions.

Due to the high volumetric energy-content of fuels, the compression ignition engine with Common Rail technology will keep enhancing human life quality for many years to come, especially when heavy duty engines are considered.