What is the Difference Between BS4 and BS6 Engines?

Bharat Stage Emission Standards (BSES), the governing organization, regulates the output of pollutants from cars operating in the country. The Indian government has enacted the Bharat Stage Emission Standards (BSES) to control pollution from automobiles and two-wheelers. From April 1, 2020, all vehicle manufacturers, both two-wheelers and four-wheelers, are required to build, sell, and register only BS6 (BSVI) vehicles. This post will teach you about the difference between BS4 and BS6 engines, their significance, and their performances.

One of the major BS4 and BS6 differences is the fuel type of these engines. The BS4 fuel has a sulphur concentration of 50ppm, whereas it is reduced in BS6 fuel to 10ppm. Hence, BS6 fuel is considered to be cleaner as compared to BS4. 

Before going deep into the difference between BS4 and BS6, let us first have a basic understanding of both of these engines.

Understanding BS4 Engines

In the year 2000, BSES, the regulatory authority for emissions from all sorts of vehicles, published the first emission rules under the moniker "India 2000." The BS2 and BS3 standards were implemented in 2005 and 2010, respectively, while BS4 standards went into force in 2017 with tougher emission limits or norms.

The laws included emission-related adjustments such as tailpipe emissions, Electronic Control Unit (ECU), ignition control, etc. The most noticeable modification was the AHO (Automatic Headlamp On), which is one of the BS4 requirements that addressed the safety component of the new emission standards.

Understanding BS6 Engines

The BS6 emission standard is the sixth generation of the emission standard, and it represents a significant improvement in pollution reduction over the previous BS4. This is also due to the BS5 (BSV) being skipped in order to migrate to stronger emission standards.

Difference Between BS6 and BS4

The following are the most significant differences between BS4 and BS6 pollution emission standards:

  • The maximum allowable limit of Nitrogen Oxides (NOx) emissions from a petrol vehicle is established at 60mg per kilometre by BS6. Whereas it was 80mg/km under BS4 standards.
  • Particulate Matter (PM) limits for petrol cars are set at fewer than 4.5 mg/km. Moving on to diesel vehicles, NOx emissions are limited to 80 mg/km under BS6 norms. BS4 standards provide the same top limit of 250 mg/km.
  • In diesel cars, BS6 standards limit hydrocarbon+NOx emissions to 170 mg/km, down from 300 mg/kg under BS4 standards.
  • Particulate Matter (PM) limits for both diesel and petrol cars have been set at 4.5 mg/km. Under BS4 regulations, this limit was established at 25 mg/km for diesel automobiles.
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