The common rail diesel injection system is a modern spin off of the direct fuel injection systems that were used in the past. On a diesel engine this system features an auxiliary high pressure fuel rail which feeds individual solenoid valves with up to 26,000 psi of fuel pressure.
The very first common rail diesel injection system was prototyped in the late 1960′s. The first successful usage of the system was in the mid 1990′s and was used on heavy duty vehicles and was eventually sold for general use in 1995. The Denso company lays claim to the offering the first common rail high pressure system also in 1995. The Bosch Company later refined the Common Rail Diesel Injection (CRDI) system. This revised system has a flexible division of a single injection into multiple pre and post injections allowing this type of system to be matched to individual engines in the best possible way to allow full combustion of the fuel delivery.
In general there is a high pressure fuel pump which creates pressure which it then stores in the systems accumulator, in many cases this accumulator is the actual fuel rail. The pressurised fuel is then fed through rigid fuel pipes into each individual injector, the injectors inject the correct amount of fuel in the form of a fine mist into the combustion chambers of the engine. The computer for the injection system is called the electronic diesel control unit or EDC for short, this controls all of the parameters of the injection system such as rail pressure, the duration of the injection and also the timing in which the injectors fire to release the fuel into the combustion chamber.
The use of piezoelectric or solenoid valves make it possible to have very fine control over the fuel injection quantity and timing, this coupled with the high pressures of the CRD system provide exceptional fuel atomisation which allows the vehicle to run cooler, burn the fuel more completely and be more environmentally friendly. In order to make the system quieter the ECD can inject a small amount of diesel just prior to the main injection event, this reduces the explosiveness and vibration inside the engine and improves cold starting. As a result, modern CRD systems require very little or no warm up time while producing much less noise than previous systems.
Different car manufacturers call the CRD system by different names, examples include: Ford Motor Company’s TDCI, GM/Opel/Vauxhall’s CDTi, Honda’s i-CTDi, Isuzu’s iTEQ, Mazda’s MZR-CD, Mitsubishi’s DI-D, Renault’s dCi, and Toyota’s D-4d. There are other variations out there but for the most part you get the idea. While they may be the same system, each manufacture renames the system in order to try to differentiate itself from the others.
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