CRDi ENGINE

Common rail direct fuel injection is a direct fuel injection system for  diesel engines.

In diesel engines, it features a high-pressure (over 1,000 bar or 100 MPa or 15,000 psi) fuel rail feeding individual solenoid valves as opposed to a low-pressure fuel pump feeding unit injectors (or pump nozzles). Third-generation common rail diesels now feature piezoelectric injectors for increased precision, with fuel pressures up to 3,000 bar (300 MPa; 44,000 psi).

In Common Rail Direct Injection, commencement of combustion takes place directly into the main combustion chamber located in a cavity on the top of the piston crown. Today, CRDi technology is being widely used to overcome some of the deficiencies of conventional Diesel engines which were sluggish, noisy and poor in performance when implemented especially in passenger vehicles.

Working of CRDi –

1. Pressure generation takes place in the high-pressure pump. The pump compresses the fuel at the pressures at about 1,000 bar or about 15,000 psi.
2. It then supplies the fuel via a high-pressure pipe to the inlet of the rail. From there, the fuel is distributed to the individual injectors, which inject it into the cylinder’s combustion chamber.

CRDI engine contains a small tube called Common rail where the injectors are connected and contains fuel at a constant high pressure of 1,350 bars. The CRDI engine small amount of fuel into the engine before the actual charge and another one afterwords.The high pressure in common rail ensures that when it injected the fuel atomizes to a very high degree and mixes evenly with the air, thereby it making very clean exhaust gas. The engine timing of fuel injected is controlled by ECU depending upon the variables such as engine speed, load, engine temperature etc.. The injectors have very precise dose of diesel into each cylinder and ECU makes sure the fuel injected at optimum moment. "This ensures lower emissions, and allows better fuel economy.

Components of CRDi System –
1. High Pressure Fuel Pump
 2. Common Fuel Rail 
3. Injectors 
4. Engine Control Unit

Advantages of CRDi:

1. Pressurized fuel is always present in the fuel line

2. Multiple injections are easily possible

3. Requisite amount and atomized fuel can be supplied, this reduces emissions.