Common Rail Direct Injection (CRDI)

Common Rail Direct Injection (CRDI) is an advanced fuel injection technology, most commonly referred to as diesel engines. This is very similar to the technology used in petrol engines and the same is differentiated by classifying it as gasoline direct injection (GDI) or fuel stratified injection (FSI). Although both these technologies have a similar design as they consist of a standard “fuel-rail” to supply fuel to the injectors, they differ considerably in pressures and the type of fuel used.

In the Common Rail Direct Injection (CRDI) system, the commencement of combustion takes place directly into the main combustion chamber located in a cavity on the top of the piston crown. Nowadays, CRDI technology is commonly used everywhere to overcome some of the deficiencies of conventional diesel engines, which were sluggish, noisy and poor in performance when implemented primarily in passenger vehicles. The line diagram of the CRDI technique is shown below in Figure.

Common rail direct injection sytem line diagram

Common rail direct injection system line diagram

The CRDI technology works with the engine control unit (ECU), which instructions from various sensors to find the exact quantity of fuel and timing of injection. The conventional injectors are replaced with solenoid-operated injectors. The injectors are opened with an ECU signal depending on engine speed, load, engine temperature, etc.

In a Common Rail system, a common fuel rail or a fuel distribution pipe is used to maintain optimum residual fuel pressure and acts as a shared fuel reservoir for all the injectors. The fuel is constantly supplied at the required injection pressure.

The pressure generation takes place in the high-pressure pump. The pump compresses the fuel at pressures at about 1,500 bar and above. It then supplies the power via a high-pressure pipe to the inlet of the rail. From there, the fuel is supplied to the individual injectors, which inject it into the cylinder’s combustion chamber.

Most of the modern diesel engines use a Unit-Injector system combined with a Turbocharger to achieve increased power output and meet stringent emission norms. Using this helps to increase power, throttle response, fuel efficiency, and control emissions.

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He is a Mechanical Engineer and Editor-in-chief of ME Mechanical. He holds a Bachelor of Engineering degree in Mechanical Engineering. He interested in the manufacturing field.

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