Common rail

From Open Encyclopedia

Common rail direct fuel injection is a modern variant of direct fuel injection system for Diesel engines. It features a high-pressure (1000+ bar) fuel rail feeding individual solenoid valves, as opposed to low-pressure fuel pump feeding pump-nozzles or high-pressure fuel line to mechanical valves controlled by cams on the camshaft. 3rd generation common rail diesels now feature piezo injectors for even greater accuracy, with fuel pressures up to 1700 bar.

Solenoid or piezo valves make possible fine electronic control over injection time and amount and high pressure provides better fuel atomisation. In order to lower engine noise, a small pilot amount of fuel can be injected just before the main load, effectively reducing its explosiveness; some advanced common rail fuel systems perform as many as five injections per stroke.

Common rail engines feature no heating up time, lower engine noise and lower emissions than older systems.

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History

Common rail engines have been used in marine and locomotive applications in times past. The Cooper-Bessemer GN-8 (circa 1942) is an example of a hydraulically operated common rail diesel engine, also know as a modified common rail.

With rising fuel prices throughout the 1990s, a number of companies, including Robert Bosch GmbH, Fiat,Volvo and MTU, attempted (separately) to develop new Diesel engines with lower emissions and higher fuel efficiency.

Common rail engines were first used by the Fiat subsidiary Alfa Romeo, and the technology is most commonly used by Fiat, under their MultiJet brandname. The engines are suitable for all types of road car, including small hatchbacks such as the Fiat Panda.

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