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BS4 to BS6 Conversion, Is it Possible?

The emission norm change from BS4 to BS6 is irreversible. On the 1st of April next month new emission norms will see a new sunrise and we’ll welcome cleaner emission norms. For automotive companies, the journey to BS6 wasn’t easy.

Read more about BS6: BS6 (Bharat Stage 6) | Explained

Many manufacturers had complications in researching and developing a new engine for the market. Though the shift involves many complex changes in and outside of the powertrain. Most of the manufacturers have done their part in developing and contributing to the new BS6 norms.

Due to this sudden turn consumers have several questions. A question arises-

Can one convert BS4 to BS6?

Can I convert BS4 to BS6? Important Question Of The Hour
BS4 to BS6 conversion? Important Question Of The Hour

BS6 In Making

Before we answer the questions lets first look into it what all has been done in order to make the engine BS6 compliant.


  • Low capacity motorcycles (50-200 cc) now come with EFI system (Electronic Fuel Injection) in order to atomize the fuel. In BS4 most of the motorcycles came with the carburetor to do the function.
  • High capacity motorcycles (200+ cc) an additional catalytic layer is added to reduce the exhaust emissions.


Diesel Engines
  • Major modifications are done in engines running on Diesel fuel as the BS6 diesel fuel is different from BS4’s. New fuel contains 5-times less sulphur than old fuel.
  • The change starts with the pumping of the fuel. New diesel engines get a redesigned fuel pump to run on low sulphur fuel.
  • The injectors on the engine too, have seen tweaks in order to pump the new fuel.
  • DPF (Diesel Particulate Filter) is added to reduce the soot and particulate matter.
  • SRC (Selective Catalytic Reduction) feature is installed into some vehicles.
Petrol Engines
  • There are changes in the new BS6 fuel but are not as prominent as diesel. Petrol being cleaner than diesel produces less emission as compared to the other part.
  • An extra filtering layer in the Catalytic converter is added to further reduce the emissions.

Considering the changes involved in developing a new engine for both, diesel as well as petrol it is really difficult to convert BS4 to BS6. There are many calculations and simulations involved which require a lot of knowledge and experience.

Suggested read: Which is the best BS6 compliant car currently sold in India?

Utkarsh Bhardwaj
Utkarsh Bhardwaj
Technical Content Strategist at GoMechanic | Big Time Petrolhead with the passion for building cars and driving those beauties.


  1. I think it’s possible to upgrade BS4 engine to BS6 as per your above post information.
    All changes mentioned can be upgraded like the injectors / nozzles and fuel pump. Second major upgrade is exhaust and installation of DPF …

    It’s correct that knowledge is required, but slow and study the upgradation to BS4 already owned engines (pre owned) will be available shortly in market

    • Hi Naik,
      It is true that with modifications, a BS4 engine can be converted to a BS6-compliant one but this requires a high level of expertise and not everybody is skilled enough to perform this job. It is therefore advised not to modify the engine if you don’t have the proper level of skillset and tools for the same.
      Stay tuned!

    • Hi Ramesh, it is possible to essentially convert a BS4 truck to comply with BS6 norms. However, the cost against such conversions will far outweigh the feasibility and will not make any sense. Thank you for commenting. Stay pinned!

  2. Car/ truck companies called backunsold BS4 cars/ trucks and ipgrafed them to BS6 stage within few thousand rupees as published in the newspapers at that time.So I feel vompany owned workshops can do this upgradation, but they ate interested in selling new cars , not on upgrading old ones to BS6 stage.Clever Business trick🙏

  3. I have bs 4 fzs bike and there is a prblm with that my cluth plate within 2 3 days I have to change my cluth plate for pickup and it can’t be solved because it has manufacturing defect so showroom told me that i can change my cluth housing to bs 6 and it will perfectly fit. So i want an opinion from all of you.
    Thank you

  4. Government has to initiaye necessary actions for supporting and encouraging the conversion of BS4 to BS6 , since people who bought the cars under loan not even yet to reach in 75% means it would ended up them for heavy loss, not even they could sell it or to complete the loan, very pathetic about the condition of middle class

    • BS6 Norms were pushed, keeping in mind the overall pollution levels in India. While BS6 as a norm is quite stringent for OEMs to deal with, without it, it is difficult to keep vehicular pollution in check, considering that Diesel engines produce more PM.


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