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Common Rail-Fuel Systems

Common Rail Explained
The Common Rail Bosch fuel system is a variation from the distribution style injection fuel system used in diesel and gas powered engines since the dawn of the fuel injection. How the Bosch Common Rail system differs from direct inject systems is that the system functions at a much higher pressure making use of a “Rail” or reservoir containing the fuel supply before it is released by injectors into the cylinders. Previously the pump would supply pressure to the injectors, and therefore fuel was under much lower pressure loads. Common Rail systems are able to take advantage of the “Common Rail” or “Common Reservoir” in which all Bosch injectors receive their fuel supply.
Common Rail Advantages
Common Rail Injection Systems outperform distributor style injection systems in all areas. The reason for this is the diesel fuel supply being injected into the engine is under much higher pressures giving the Bosch injection system the ability to atomize the fuel into a finer mist. This leads to more complete combustion.
  Bosch Injection 3rd Generation Common Rail System Traditional Distributor Style Injection System
Emissions 20% Lower  
Power 5% Power Increase  
Fuel Economy 3% Lower Fuel Economy  
Engine Noise 3 dB less  
Vehicle warm up time Not needed A few minutes
Over the course of 100,000 miles the Bosch fuel injection pump will save the average owner approximately $500 in diesel fuel cost (3%, 17.5 mpg, $3 per gallon). The noise reduction comes from the Common Rail Injectors making a “pilot injection” before the injection that powers the engine stroke. This creates a noise dampening effect within the engine.
History of Common Rail
1942 The Cooper-Bessemer GN-8 was first build as the first diesel powered engine using Common Rail technology. This technology was only used in very large machines such as maritime and locomotive engines.

1960 Mr. Hiber of Switzerland devises a Common Rail system using fuel injectors. The Swiss Federal Institute of Technology works on further developing this technology. Common Rail was not ready for mass production as this time.

1990s Magneti Marelli, Centro Recerche Fiat and Elasis collaborate to develop the Common Rail System for the Fiat Group. Fiat is able to make many break troughs with this technology however they are not able to develop a product that is ready for mass production.

1990s Bosch acquires the patents from the Fiat Group and works towards making a mass produced version of the common rail system. Bosh develops the entire fuel delivery system using a Bosch fuel Injector, Bosch fuel pump, as part of the entire Bosch fuel injection system.

1994 The first Common Rail Bosh injection pump is installed in a truck. This Diesel injector pump is referred to as the P7100.

1997 Installation of the first Common Rail system in a passenger vehicle is completed as part of the overall Bosch fuel component strategy.

1998 Bosh pumps used in truck applications are improved and the second generation of diesel injection the VP44 pump for the Common Rail System is developed.

2003 The division of the company that makes Bosch injection pumps introduces the third generation of diesel injection for trucks the CP3 Bosch pump Common Rail System.
Future of Common Rail
Common Rail has also been introduced for cars in the EU. In 1999 diesel car sales accounted for 28% of car sales in the EU. With help in large part from the Bosch fuel system development the small car diesel engine sales increased to 52% of the car sales by the end of 2007. There has been some retraction of diesel automobile growth cause largely in part due to their higher initial cost. Now diesel car sales represent 46% of the EU market. Other considerations for this decline is the higher cost of maintenance on the diesel cars due to emission control devices and more complex systems need on the vehicle such as the Common Rail system. This has led to a resurgence of the gasoline powered engines in the near term.