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difference between bs4 and bs6

How BS6 Engine is Different From the BS4 Engine?


In order to control pollution emitted by automobiles, the Central Pollution Control Board (CPCB) introduced regulations known as Bharat Stage Emission Standards (BSES). These emission standards have been made compulsory by India’s government to control air pollutants emitted by the internal combustion engine of vehicles. BSES norms were first introduced in 2000 under the head ‘India 2000’. Then BS2 and BS3 were introduced in 2005 and 2010, respectively. 

After this, the emission norms became more stringent with the enforcement of Bharat Stage IV (BS4). Thereafter, the government of India decided to do away with the implementation of BS5 in 2016 and instead introduced Bharat Stage VI (BS6) in 2020. In this article, we will discuss major differences between the BS4 and BS6 engine and the performance of the BS6 engine.

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What is BS4?

The Bharat stage 4 norms were introduced in 2017. As per these standards, 50 parts per million sulphur content was permitted as opposed to 10 parts per million mandated now by the BS6 norms. 

What is BS6?

BS6 is the sixth iteration of the vehicular emission norms and is relatively stricter to help cut down emissions by a good margin. As per this new emission standard, all vehicle manufacturers – both two-wheelers and four-wheelers – are required to manufacture and sell only BS6 (BSVI) compliant vehicles.

Differences between BS4 and BS6 engines

Compared to BS4, BS6 norms are stricter. A major difference between the two engines is that the BS6 engine requires fuel containing five times lower sulphur traces as compared to the BS4-fuelled engine. While the content of sulphur in BS4 fuel is 50ppm, it is 10ppm in BS6 fuel.

Also, NOx (Nitrogen Oxide) content in BS6 compliant petrol vehicles has been reduced from 80mg/km to 60mg/km. The BS6 norms aim at reducing three pollutants in diesel engines – HC (Hydrocarbons) + NOx, PM (Particulate Matter), and NOx reduction – by 43, 68, and 82 per cent, respectively. 

Real Driving Emission (RDE) has been introduced in the BS6 norms to make sure the emission from the motor vehicle is measured on a real-time basis. This was not the case in BS4 norms. Another feature added to BS6 engines is the Onboard Diagnostic (OD), which was not available in the BS4 engine.

Can a BS4 engine run on BS6 fuel?

The answer is yes. A BS4 engine can run using BS6 fuel without any complications, especially if it’s a petrol car. Talking about diesel cars, the sulphur content in the fuel acts as a lubricant for fuel injectors. As BS6 fuel has 10ppm sulphur content in comparison to BS4 fuel (50ppm), it could impact the fuel injector in the long run due to lack of lubrication.

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Can a BS6 engine run on BS4 fuel? 

In this case, also petrol engines will face no issues at all as the fuel composition is not that different. However, when a BS6 diesel engine runs on S4 fuel, it will increase the emissions, decrease fuel economy, and might also cause issues in the fuel delivery system.

Health and environmental effects of air pollution in India

The pollution emitted by vehicles in India is measured by government agencies using the Air Quality Index (AQI). The AQI uses the below criteria to measure:

  • Nitrogen Oxide
  • Sulphur Oxide
  • Ozone
  • Carbon Monoxide
  • Particulate matter 

Some of the effects of pollution on health are as follows:

  • Cancer
  • Lethargy
  • Heart ailment
  • Respiratory ailment
  • Itchy eyes
  • Anaemia
  • Lower alertness
  • Throat and lung infections
  • Asthma

The effects of higher pollution levels on the environment are:

  • Global warming
  • Smog
  • Acid rain
  • Contamination of air, water, and soil
  • Exhaustion of fossil fuel

BS6 cars in India

From April 1, 2020, all new cars are being manufactured and registered in compliance with BS6 emission norms. As of now, BS6 cars are being offered by Hyundai, Maruti Suzuki, Mahindra, Tata, Kia, Toyota and more. While some models such as Mahindra Thar, Hyundai Creta, Hyundai i20, and Kia Seltos get BS6-compliant petrol and diesel engines, cars like Maruti Swift, Maruti Baleno, Maruti Vitara Brezza and Nissan Magnite are available with BS6-compliant petrol engines. 

What’s next after BS6?

Currently, no new emission norms have been set by the governing body. However, a second version of the BS6 may get introduced in the near future, which will include Real Driving Emissions (RDE) cycle. The Automotive Research Association of India (ARAI) will ascertain the level of pollution by testing new vehicles in real-world conditions. Currently, the test is being performed in a controlled environment.

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In conclusion, there’s no denying the fact that the introduction of BS6 emission norms are the government’s best strategy to control rising levels of pollution in major metro cities across the country. If the pollution level is reduced, it will lower the negative health effects and result in a healthy environment. 

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