MPFI Technology In Plain English


I was commuting with my friends back from office one evening when one of them asked me

What is an MPFI Engine?

You must have seen cars with specifications which mention words like MPFI and CRDI or CRDE. To an automotive engineer or enthusiast, it means something, but for a common man, it may not make much sense.

MPFI Engine

In this article I will talk about MPFI in simple English so that a person who is not an automobile engineer can also make sense of it.

MPFI means – Multi-point Fuel-Injection (also called fuel-injection system)

The term MPFI is used to specify a technology used in Gasoline/petrol Engines. For Diesel Engines, there is a similar technology called CRDI. We will discuss CRDI in a separate article to avoid confusion.

MPFI System is a system which uses a small computer (yes, a small computer without keyboard or mouse, its more like a microchip) to control the Car’s Engine. A Petrol car’s engine usually has three or more cylinders or fuel burning zones. So in case of an MPFI engine, there is one fuel –injector installed near each cylinder, that is why they call it Multi-point (more than one points) Fuel Injection.

In plain words, to burn petrol in an Engine to produce power, Petrol has to be mixed with some air, ignited in a cylinder (also called combustion chamber), which produces energy and runs the engine. I will not talk of further internal details because it will make this article for Engineers and not common people.

Before MPFI system was discovered, there was a technology called “Carburetor”. Carburetor was one chamber where petrol and air was mixed in a fixed ratio and then sent to cylinders to burn it to produce power. This system is purely a mechanical machine with little or no intelligence. It was not very efficient in burning petrol, it will burn more petrol than needed at times and will produce more pollution. But with the advancement of technology this was about to change.

MPFI emerged an Intelligent way to do what the Carburetor does. In MPFI system, each cylinder has one injector (which makes it multi-point). Each of these Injectors are controlled by one central car computer. This computer is a small micro-processor, which keeps telling each Injector about how much petrol and at what time it needs to inject near the cylinder so that only the required amount of petrol goes into the cylinder at the right moment.

So the working of MPFI is similar to Carburetor, but in an improved way, because now each cylinder is treated independently unlike Carburetor. But one major Key difference is that MPFI is an intelligent system and Carburetor is not. MPFI systems are controlled by a computer which does lots of calculations before deciding what amount of petrol will go into what cylinder at a particular point in time. It makes that decision based on the inputs it reads.

For the Inputs, the microprocessor (or car’s computer) reads a number of sensors. Through these sensors, the microprocessor knows the temperature of the Engine, the Speed of the Engine, it knows the load on the Engine, it knows how hard you have pressed the accelerator, it knows whether the Engine is idling at a traffic signal or it is actually running the car, it knows the air-pressure near the cylinders, it knows the amount of oxygen coming out of the exhaust pipe.

Based on all these inputs from the sensors, the computer in the MPFI system decides what amount of fuel to inject. Thus it makes it fuel efficient as it knows what amount of petrol should go in. To make things more interesting, the system also learns from the drivers driving habits. Modern car’s computers have memory, which will remember your driving style and will behave in a way so that you get the desired power output from engine based on your driving style. For example, if you have a habit of speedy pick-up, car’s computer will remember that and will give you more power at low engine speeds by putting extra petrol, so that you get a good pick-up. It will typically judge this by the amount of pressure you put on accelerator.

So the cars of today are really intelligent, well not as intelligent as drivers 😉 but fairly intelligent to keep pollution under control and saving the fuel.

Stay tuned for an article on CRDI, which is like an MPFI parallel for Diesel Engines.

What is CRDI In Simple English?

What is GDI (Gasoline Direct Injection)?

What is Turbocharger? What is Supercharger?

PS : I have deliberately used least jargons and kept it as simple as I could. Please leave your comments or suggestions. Also check out the article on Future of Cars.

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  1. nice 1…stumbled it…
    btw, i nvr cud figure out y dere’s a warning in all MPFI cars to start without depressing d throttle…i knw its not gud otherwise, bt y nt d suggestion, y d warning?
    n ya, is it really impossible to push-start an MPFI engine? should i always carry jump-leads, just like d manual suggests?

  2. @actinium
    Thanks for the appreciation.
    The warning is there because people who are used to of old cars start the engine with throttle depressed. As the MPFI system uses this as an input via a sensor, so it may cause engine to unnecessarily rev to a very high rpm when its idle. This is not good especially for a cold start early morning as it increases engine wear and tear.

    Regarding push start, once one of my cousin’s car’s battery went too weak, so we pushed start it, it worked with that, he has a Zen Vxi 2005 which is an MPFI car. I can’t say for sure about other cars.

  3. It’s a good one. I have one doubt. i.e., What is the minimum amount of petrol to be maintained in cars with MPFI engine ?

  4. @mohan
    for any car, i would say you should have enough fuel to keep you equipped to reach the nearest petrol-filling station. I would recommend to keep at least 5 liters of fuel always in your fuel tank, rest is up to your discretion.

  5. @Arun
    conceptually MPFI is gives better fuel efficiency, practically also, a well tunes MPFI will give better fuel efficiency than carburetor.

  6. MPFI is a quite old technology if you as me however, a lot of cars are still using this. There is also a technology that came inbetween MPFI and Carb engines. This was SPFI (Single point fuel injection). This was cheaper however was only slightly better than the carb engines. One of the biggest problems that SPFI and Carb engines faces is that once the air fuel mixture is created it has to travel a long distance in varying environment before it gets used. This caused problems like losses due to wall sticking as well as condensation leading to bigger molecules of fuel ( reducing the atomization!!) etc. MPFI also had flavors like Sequential, Continuous etc..

  7. The details is good. But major disadvantage with MPFi i.e, injectors is once if it is removed it cant be used again. Chemicals are available which is just like a fuel to cleanup the carbon deposit of the injectors.

  8. Well the difference depends on what type of MPFI system you are having. Also, if there are other technologies combined with MPFI. E.g EGR (Exhaust Gas Recirculation) & Variable intake Manifold. For example Wagon-R MPFI give you about 12-14 Kmpl. In carb systems you could get about 9-12 Kmpl depending on your riding. Also, emissions wise you will be polluting less with MPFI with ECU control.

  9. well in ur article it has been said that MPFI uses different fuel injectors for different cylinders but when MPFI technology was not developed how the fuel inject in Carb inject fuel in different cylinders.

  10. hi,

    this is fantastic article. provided very good insight on MPFI. thank you very much for explaining it in such a lucid language.

  11. @Rahul
    In Carb engines there is no need of a pump. What happens is that there is a very fine nozzel which opens into something known as a venturi. Because the venturi has a lower pressure the fuel is sucked into the system. The problem here is that as the vehicle moves on different inclinations (i.e up hill down hill etc) there is a variation in the fuel flow. If you are wondering who is really causing the suction… is the vaccum created by the engine….note that the engine actually acts like a pump.

  12. Hi Excelent job

    You have understood the need to educate laypeople like me. (A risky job)
    I have bougt a Indigo CS GLX (Petrrol) whci has a MPFI engine.

    Any suggestions on maintainance and improveing fule efficiency.

    I have driven 800 KMS and at presetn get 9.5 KMPL with occational AC city driving.

    Some say they get 14 on Highway without AC

    THanks for your help


  13. There are couple of things that you need to do perhaps
    1. Drive sensibly without unnecessary racing of the engine. The ECU controlled systems have sufficient knowledge to avoid engine stall.
    2. Ensure that your Lambda sensor ( Oxygen sensor) in the exhaust is working properly. This acts like a feedback to the ECU and without this the ECU is almost blinded.
    With 2/3 service you milage should actually increase ( after oil changes)

  14. Nice one…………………… Very nicely explained in simple words………….. What do u think will be the next step of development in this technology ?

  15. @Arun
    Next level is already there and it is called GDI ( Gasoline Direct Injection). Anyway that is what is popular…but again there is something that is called HCCI ( Homogenous Charge Compression Ignition). This is a GM based technology which removes the spark plug from Petrol Engines and make them same as Diesel Engines.So actually MPFI is quite a old technology…

  16. I have a doubt.-If the engine is a single cylinder petrol engine with FI(like HH glamour pgm Fi /P220DTS-Fi), is it called mpfi?

  17. are there any different technique to drive a mpfi engine car than a pld onme..
    i mean how does one use the clutch and accelerator combination for such engines…

  18. A nice article for the layman to understand without jargon.
    When buying a car what are the points one has to check ?

  19. Hi, Details are informative.
    This article have cleared my some doubts which were before reading this article.
    Thank you

  20. The details is good. But major disadvantage with MPFi i.e, injectors is once if it is removed it cant be used again. Chemicals are available which is just like a fuel to cleanup the carbon deposit of the injectors.

  21. @Aswin
    This technology already exists for bikes, bit only in few bikes because of the cost of the system makes it expansive. Some bikes like Yamaha R15 , Karizma ZMR , Hero Honda Glamour FI version etc are few bikes which use this technology. Also most modern racing bikes have fuel injection systems instead of Carburettor.

  22. hello dude

    ur article was awesome
    m doing btech please tell me the effect on engine due to mpfi system and

    wats the advantage over carburettorssss


  23. awesome article buddy….

    it could not be explained much simpler than that…. a very nice article..

  24. Hi Rohit,

    Actually I am not an automobile engineer but as you said even non automobile engineer like me understood the concept which you explained. Thanks a lot

  25. Hi Rohit,

    I have gone through your MPFI & CRDI Article. Its very nice Article. I think, no one can give more than this elaberate & easier explanation to understand. Keep it up & update more as much you can.

    Thanks for your most valuable article & information.


  26. Hey, Good Article..
    I’m just curious about why petrol engines are not improving on their mileages (KMPL) while diesel engines seems to give good average at low fuel cost.

  27. nice blog man! but i want to ask you that can we use this technology in 2 strokes engines, i am asking this u because i guess mpfi system will help in reducing scavenging and will increase the efficiency of the engine if yes then please tell how can i applied it to 2 stroke 2 cylinder engine( RD 350 engine) please give me classified details thnak you!

  28. Good article.Simply explained the complicated working technology.Lot of people are still starting the cars with a fully pressed pedal.

  29. […] and guess what, its coming to India next week. The second Generation S60 features a variety of MPFI petrol engines and CRDI diesel engines across various models and trim levels. The Volvo […]

  30. Theres a mistake that u made saying about oxygen coming out the exhaust. Please correct it. Other than that, this is pretty good for commons.

  31. Nice article…I am going to buy Indica eV2 GLX..(MPFI)..25 km/l mileage…
    Is this car really going to give me that much fuel efficiency…?????

  32. Dear Sir,

    I have one confusion i have Hyundai Accent i had fitted CNG kit on this vehicle. which type of precaution i have to maintain my vehicle to serve better performance.

  33. it is an automobile engineer and i knew almost all abt these kinda for others it ll be so usefull..hope mechanical engineers ll understand abt these which they cant learn in their acadamics..

  34. Thanks for the article…. I am a marine engineer and i work on very big engines… A nice article to understand car engine system…

  35. Hi,

    Nice article. Clears lot of doubt s.
    I’m not sure if this has been asked before. Sorry if it has been but I couldn’t find it.

    Which technology is better crdi or mpfi. If one is better than the other then can that technology be designed for both petrol as well as diesel engine.


  36. Clarifying on my query from before, is multi point injection more efficient or common rail and could both technologies be used for diesel as well as petrol engine



  37. rohit nyc …one ……please tell me injector inject the petrol but, but about air ….air is also used in combustion chamber