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 stored pressure in an accumulator integrated into the injector body, with injection subsequently triggered mechanically. The first solution was widely adopted, as the second offered no real advantage in a fully mechanical setup. The jerk-type system with a sharp cam is still in use today.

With the advent of electronics in the 1960s, the pressure-accumulating concept got a second chance. Electromagnetically actuated injectors were developed, allowing the injection process to be flexibly controlled via an electronic control unit (ECU). A high-pressure pump generates fuel pressure for all injectors, and the pressurized fuel is delivered through a “common rail.” This flexibility in optimizing diesel injection paved the way for modern Common Rail technology.

Production of Common Rail systems began in 1997 for both passenger car and marine diesel engines. In the truck engine sector, Common Rail injection achieved widespread adoption during the first decade of the 21st century.

A Technical Revolution

Common Rail injection revolutionized the diesel engine. Passenger cars have achieved specific power outputs exceeding 100 horsepower per liter of displacement, and torque values of 200 newton-meters per liter—all while maintaining remarkably low fuel consumption and meeting exhaust emission standards that would have seemed impossible just a few years earlier.

Today, Common Rail systems have completely replaced the jerk-type systems in both passenger car and truck applications. In the field of large diesel engines – including those for diesel-electric locomotives, ships, heavy earthmoving machinery, and power generation – widespread implementation is still underway.

Common Rail technology is also a key enabler in the use of renewable, CO₂-neutral fuels in compression-ignition diesel engines – the most thermodynamically efficient combustion process. A new era of carbon-neutral internal combustion engines has begun.

Thanks to the flexibility of electronically controlled injection, Common Rail systems are well-suited for the use of green fuels. They will play a crucial role in creating a future free of pollutant and greenhouse gas emissions from tailpipes.

Due to the high volumetric energy content of liquid fuels, compression-ignition engines with Common Rail technology will to enhance quality of life for years to come – especially in heavy-duty applications.