CRDI Technology In Plain English


Ever since I wrote about the MPFI Technology , I wanted to cover CRDI also. In this article, I have used simple words and terms that help you easily understand how things work with CRDI / CRDe / DICOR / TDI etc. If I have to draw an analogy, I would say CRDI is for Diesel Engine as MPFI is for Gasoline/Petrol Engine.

CRDI Engine

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Common Rail Direct Injection or CRDI

CRDI is an intelligent way of controlling a diesel engine with use of modern computer systems. CRDI helps to improve the power, performance and reduce harmful emissions from a diesel engine. Conventional Diesel Engines (non-CRDI engines) are sluggish, noisy and  poor in performance compared to a CRDI engine.

CRDI or common rail direct injection system is also sometimes referred to by many similar or different names. Some brands use name CRDe / DICOR / Turbojet / DDIS / TDI etc. All these systems work on same principles with slight variations and enhancements here and there.

CRDI system uses common rail which is like one single rail or fuel channel which contains diesel compresses at high pressure. This is a called a common rail because there is one single pump which compresses the diesel and one single rail which contains that compressed fuel. In conventional diesel engines, there will be as many pumps and fuel rails as there are cylinders.

As an example, for a conventional 4 cylinder diesel engine there will be 4 fuel-pumps, 4 fuel rails each feeding to one cylinder. In CRDI, there will be one fuel rail for all 4 cylinders so that the fuel for all the cylinders is pressurized at same pressure.

The fuel is injected into each engine cylinder at a particular time interval based on the position of moving piston inside the cylinder. In a conventional non-CRDI system, this interval and the fuel quantity  was determined by mechanical components, but in a CRDI system this time interval and timing etc are all controlled by a central computer or microprocessor based control system.

To run a CRDI system, the microprocessor works with input from multiple sensors. Based on the input from these sensors, the microprocessor can calculate the precise amount of the diesel and the timing when the diesel should be injected inside the cylinder. Using these calculations, the CRDI control system delivers the right amount of diesel at the right time to allow best possible output with least emissions and least possible  wastage of fuel.

The input sensors include Accelerator Pedal Position (APP) sensor, crank position sensor, pressure sensor, lambda sensor etc. The use of sensors and microprocessor to control the engine makes most efficient use of the fuel and also improved the power, fuel-economy and performance of the engine by managing it in a much better way.

One more major difference between a CRDI and conventional diesel engine is the way the fuel Injectors are controlled. In case of a conventional Engine, the fuel injectors are controlled by mechanical components to operate the fuel injectors. Use of these mechanical components adds additional noise as there are many moving components in the injector mechanism of a conventional diesel engine. In case of a CRDI engine, the fuel injectors are operated using solenoid valves which operate on electric current and do not require complex and noisy mechanical arrangement to operate the fuel Injection into the cylinder. The solenoid valves are operated by the central microprocessor of the CRDI control system based on the inputs from the sensors used in the system.

So if I summarize it, CRDI works on intelligently controlling the Diesel Engine by using sensors and microprocessors. It replaces some of the mechanical components with intelligent electrical and electronic systems which improves the power, response, efficiency and performance. It also reduces the noise, emissions and vibration levels to a considerable extent.

I hope I have used simple words so that you don’t get confused in the technical jargons.

check out more-

What is MPFI In Simple English?

What is GDI (Gasoline Direct Injection)?

What is Turbocharger? What is Supercharger?

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  1. tks… vry briefly explained bout CRDI… n very sducating. Plz keep on posting regarding the latest coming technologies these days.

  2. This info was excelent for me as I am interestedin buying a car. But then why do we rate fiat Quadrajet diesel engine as one of the best. Why cant TATA come up with same tecno. I am planning to go for TATA VENTURE, can U pls tell me what engine is there inside. Why did tata used aTDI engine when it has Quadrajet in other cars and selling like hot cakes. Venture is a hard hitting compition for eeco or omni then why not have fiat diesel engine for it. Secondly, Venture is having 1.4l engine in spite of that the van claims top speed of 125KMPH whereas India which is having 1.2l run at 144 KMPH. WHY? Pls can U tell me if I can go for Venture or settle for Tata Ignis. U can suggest on my mail also. THANKYOU for… Venture is launching in July 2010.

  3. What are the fullform of diesel engine like CRDI, CRDe, TDI, DICOR, WHAT ENGINE IS THERE IN VENTURE AND HOW EFFICIENT IS IT . Why is it that the car has 1.4 l and still the speed is 125KMPH . what is the diff between this eng and quadrajet engine. Thankyou

  4. Like CDRI where injectors are operated by solenoids can the ENGINE VALVES also eliminated by using solenoids with computer controlled operation.

  5. @K L Pai
    very intelligent point raised by you. For valves, there is something called valve timings, which actually describe the performance and functionality of valves. To control valve timings, there are systems like VVT, VVTI,IVTEC etc. Some of these are computer controlled. But use of solenoid type device is not feasible as there is tremendous strength required to operate valves as there is high pressure involved in the operation of valves.
    you can read more about VVTI here –

  6. Thanks for the info. I am contemplating buying a vehicle with CRDI engine and no salesman can explain how it works.

  7. I owned a CRDI car, I’m very pleased with the performance of this technology. An unfortunate event happens, my car was submerged to the flood. The service center did well in restoring my car however I noticed that the speed and power decreases and engine becomes a little bit noisy. May I know what are the reasons and how to restore it and retunr back the original efficiency. Thanks

  8. @emer rivera
    Sad to know that your car got submerged. There may have been some damages which caused engine components to be in not-so-good shape. To make it better, get it checked and get some more repairs if necessary. Better quality engine oil will help reduce some of the noise. Also, insist on getting the engine mounts inspected, also get all the nuts and bolts checked for any loose parts which might be creating noise.

  9. While I appreciate your effort to explain CRDi in layman’s terms, your article seems to give an impression that CRDi is mostly about single computer controlled injection of fuel into mutliple cyclinders.

    The main feature of CRDi is that is has a rail of highly pressurized diesel, common to all cyclinders. From this rail, diesel is injected into cylinders using microprocessors (this can be done in non-CRDI also, please note). Since the injected diesel is highly pressurized to begin with, it ensures extremely efficient burning of diesel in chamber leading to higher power and less soot in exaust.

    In summary, the biggest problem with conventional diesel engines was that diesel was not being burnt most efficiently, leading to low power and soot in exaust. By using CRDi, pressurized fuel is injected into engine leading to efficient burning, more power and less soot in exaust.

  10. Thank u very much..This is very simple and educative.Can you please explain the difference between PumpDuce and TDI of Wolkswagon Engines

  11. […] a turbocharger to the 1.3 litre engine which powers diesel cars from Maruti. This turbocharged CRDI Diesel Engine will power the Diesel variant of the Maruti SX4 which is due for launch in the year 2011. As per […]

  12. i have a verna CRDi mar 2007 model, total run 87000km. i seem There is a problem in pick up of my car, when i press the acceletor it not move fast., it move slowley slowly,, one thing more after 4000rpm speed of engien it leaves very black coulor smoke, more than normal
    but happen can be.. plz reply
    plz dont mind i am weak in english.

  13. Can somebody compare the mechanism of CRDI and older version engine with diagram….wanna understand more in detail……

  14. All the older non electronic diesels I ever worked on have only 1 pump/distributor on them, .whereas common rails have a lift pump in the tank as well. Indirect engines were also neither sluggish or noisy, even non turbo versions.
    More importantly they do not suffer from electronic glitches, piezo failures, sensor failures and other computer bases faults.
    That said, these new engines are more fuel efficient and slightly cleaner in that diesels produce far less Co2 than petrol anyway.

  15. Thanks a million
    The Explanation was excellent. I complete understood the working of CRDi diesel engine. I Mean the way you expresses all that was so simple that everyone could understand it to its full extent.

  16. I own a VW Vento TDI. It has run 54000 kms. I am facing a problem with the fuel system. The dealer has quoted me Rs. 2.2 lacs for rectification / replacement of the system. The reason given is poor quality of diesel. I fill up the diesel from a company owned pump on regular basis. Besided that I do not have any control on it.
    I am personnaly not comfortable as it is a huge amount and the problem could recurr.
    Is it possible to alter the fuel system with a robust branded one. Please guide me if you have / know expertize in the area and who would do it.
    Please furnish me the contact details of the person.
    I reside in Kalyan near Mumbai.


  17. Hi Rohit,
    Thats a great article. That explained precisely how things might be working to a person like me who is not from automobile background but highly intrested in the same.

    Thanks a lot and keep up the good work !!


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