Common rail direct fuel injection is a fuel system that is employed in most of the present diesel cars in the world. It is modified form of direct fuel injection system that is used in petrol and diesel engines. CRDI helps to improve the performance, power and reduce harmful emission from diesel engines.
What Is CRDI OR COMMON RAIL DIRECT FUEL INJECTION?
As the name suggest CRDI uses a common rail or a common fuel channel which contains diesel compressed at high pressure(over 1,000 bar;15,000psi).This is called common rail because it contains one single pump that compresses the diesel and one single rail that that contains the compressed form of diesel. Previously, most of the diesel engine contains as many pumps and fuel rails as there are cylinders. In the starting of CRDI diesel engine, solenoid valves is used that is now replaced by piezoelectric injectors in third-generation CRDI engine. Piezoelectric injectors is used for there ability of having great precision and they can hold a fuel pressure up to 3,000 bar(44,000 psi).
CRDI-stands for Common Rail Diesel Injection. It’s a type of diesel engine, was considered to be the revolution in fuel injection system and was invented by Fiat in 1995. Fiat calls it MultiJet, and name goes on changing according to company, but technology under the hood remains the same. Hundai and Kia call it CRDI.
CRDi demonstrates direct injection of the fuel into the cylinders of a diesel engine via a single, common line, called the common rail which is connected to all the fuel injectors.
Whereas ordinary diesel direct fuel- have to build up pressure anew for each and every injection cycle, the new common rail (line) engines maintain constant pressure regardless of the injection sequence. This pressure then remains permanently available throughout the fuel line. The engine’s electronic timing regulates injection pressure according to engine speed and load. The ECU modifies injection pressure precisely and as needed, based on data obtained from sensors on the cam and crankshafts. In other words, compression and injection occur independently of each other. This technique allows fuel to be injected as needed, saving fuel and lowering emissions.
WORKING OF CRDI ENGINE
In modern CRDI engines, the injectors are controlled by engine control unit(ECU) which opens each injector electronically rather than mechanically. The time interval and timing of the fuel injection are all controlled by microprocessor based control system. The microprocessor get input from various multiple sensors and based on that input it calculate the amount of diesel and the timing when the diesel should be injected in each cylinder. Most of the CRDI engine uses Accelerator Pedal Position sensor, crank position sensor, pressure sensor etc. These sensors and microprocessors help to get maximum output from a diesel engine and also improve factors like fuel economy, power etc.
All the automotive manufacturers refer to their CRDI engine by there own brand names. Following is the list of some companies that uses CRDI engines.
The common rail system or CRDI system is suitable for al the types of road cars with a diesel engine. The use of microprocessors and various sensors helps to improve the power, efficiency, noise, vibrations and many more factors to a great extent than the conventional or non-CRDI Diesel engine.
Advantages and Disadvantages of CRDI
CRDI System has lots of advantages like with this technology more power is developed by engine, It increased fuel efficiency, reduced noise, Increase stability, pollutants are reduced, particulates of exhaust are reduced, exhaust gas re circulation is enhanced, precise injection timing is obtained, pilot and post injection increase the combustion quality, more pulverization of fuel is obtained, very high injection pressure can be achieved, the powerful microcomputer make the whole system more perfect, it doubles the torque at lower engine speeds.
The main disadvantage is that this technology increase the cost of the engine. Also this technology can’t be employed to ordinary engines.
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