Common Rail Direct Injection (CRDi):
Most modern engine fuel systems use an advanced technology known as CRDi or Common Rail Direct Injection. Both petrol and diesel engines use a common 'fuel-rail' which supplies the fuel to injectors. However, in diesel engines, manufacturers refer to this technology as CRDi, whereas Petrol engines term it as Gasoline Direct Injection (GDI) or Fuel Stratified Injection (FSI). Both these technologies have a similarity in design since they consist of a 'fuel-rail' that supplies fuel to injectors. However, they considerably differ from each other on parameters such as pressure & type of fuel used.
Besides, in Common Rail Direct Injection, the combustion occurs directly into the main combustion chamber located in a cavity above the piston crown. Today, manufacturers use CRDi technology to overcome some of the deficiencies of conventional diesel engines, which were sluggish, noisy, and poor in performance when implemented, especially in passenger vehicles.
Following is the schematic CRDi line diagram:
The CRDi technology works in tandem with the engine ECU, which gets inputs from various sensors. It then calculates the precise quantity of fuel and timing of injection. The fuel system features components that are more intelligent in nature and controls them electrically / electronically. Additionally, the conventional injectors are replaced with more advanced, electrically operated solenoid injectors. They are opened by an ECU signal, depending upon the variables such as engine speed, load, engine temperature, etc.
Furthermore, a Common Rail system uses a fuel-rail or, in simple words, a 'fuel distribution pipe' that is common for all cylinders. It maintains optimum residual fuel pressure and also acts as a shared fuel reservoir for all the injectors. In the CRDi system, the fuel-rail constantly stores and supplies the fuel to the solenoid valve injectors at the required pressure. This is quite opposite to the fuel injection pump supplying diesel thru’ independent fuel lines to injectors in case of earlier generation (DI) design.
Components of Common Rail Direct Injection System –
1. High Pressure Fuel Pump
2. Common Fuel Rail