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HISTORY The common rail system prototype was developed in the late sixties by Mr. Hiber of Switzerland. After that, Ganser of the Swiss Federal Institute Of Technology focusing on his research the common rail technology was advanced. In mid nineties, Dr. Shohei Itoh and Masahiko Miyaki, Japanese automotive parts manufacturer Denso Corporation , developed the Common Rail Fuel System for Heavy Duty Vehicles and finally turned into its first practical use on their ECD-U2 common Rail system, which was mounted on the HINO RAISING RANGER truck and sold for general use in 1995. Later in 1997 the German automotive parts manufacturer Robert Bosch GmbH extended its use for passenger car. 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 . COMMON RAIL TODAY Today the common rail system is responsible for a revolution in diesel engine technology. Delphi Automotive Systems of the US also make common-rail systems. Different car makers refer to their common rail engines by different names, e.g. DaimlerChrysler's CDI, Ford Motor Company's TDCi (most of these engines are manufactured by PSA), Fiat Group's (Fiat, Alfa Romeo and Lancia) JTD, Renault's DCi, GM/Opel's CDTi (most of these engines are manufactured by Fiat, other by Isuzu), Hyundai's CRDI, Mitsubishi's DI-D, PSA Peugeot Citroen's HDI , Toyota's D-4D, and so on. PRINCIPLES 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. In older diesel engines, a distributor-type injection pump, regulated by the engine, supplies bursts of fuel to injectors which are simply nozzles through which the diesel is sprayed into the engine's combustion chamber. As the fuel is at low pressure and there cannot be precise control of fuel delivery, the spray is relatively coarse and the combustion process is relatively crude and inefficient. In common rail systems, the distributor injection pump is eliminated. Instead an extremely high pressure pump stores a reservoir of fuel at high pressure - up to 1,800 bar (180 MPa ) - in a "common rail", basically a tube which in turn branches off to computer-controlled injector valves, each of which contains a precision-machined nozzle and a plunger driven by a Solenoid . Driven by a computer (which also controls the amount of fuel to the pump), the valves, rather than pump timing, control the precise moment when the fuel injection into the cylinder occurs and also allow the pressure at which the fuel is injected into the cylinders to be increased. As a result, the fuel that is injected atomises easily and burns cleanly, reducing exhaust emissions and increasing efficiency. In addition, the engine's Electronic Control Unit (ECU) can inject a small amount of diesel just before the main injection event ("pilot" injection) that reduces noise and vibration, as well as optimises injection timing and quantity for variations in fuel quality, cold starting, and so on. Most European automakers have common rail diesels in their model lineups, even for commercial vehicles. Some Japanese manufacturers, such as Toyota, Nissan and recently Honda, have also developed common rail diesel engines. SEE ALSO EXTERNAL LINKS |
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