Comparison between BS-IV and BS-VI Motor Vehicles

A new emission norm is going to be permanently implemented from the 1st of April this year. This emission norm is Bharat Stage VI known as BS-VI.  BS-VI is the latest emission norms in India as of now which is applicable for both petrol and diesels.

What is Bharat Stage?

Bharat Stage refers to the emission standards that are instituted by the Government of India. These standards regulate the output of the exhaust pollutants from an Internal combustion engine equipped motor vehicle. These limits are set by the Central Pollution Control Board. As European countries have EURO, India has its own BS.

Why BS V was skipped?

Bharat stage V was skipped just because the level of air pollutants from the exhaust emissions reached at an alarming level which is very harmful for the environment. In 2017, when New Delhi has pollution levels increased to high level then the Aam Aadmi Party the then ruling New delhi, demanded Bharat stage VI. So Bharat stage VI implementation was not possible to bring it back in 2017 so it took almost three years to implement this i.e., in 2020. So it was decided to skip the Bharat stage V and to implement Bharat stage 6 over the Bharat stage V emission norm from bharat stage IV. The Bharat stage VI is more cleaner than the Bharat stage V and the previous Bharat stage IV emission norm.

Major pollutants from vehicles:

There are various pollutants which are emitted by Internal Combustion Engine, Spark Ignition engine, Compression Ignition engine that are eqipped in motor vehicle. The major types of pollutants are

  • Carbon dioxide (CO2)
  • Carbon monoxide (CO)
  • Hydrocarbons (HC)
  • Oxides of Nitrogen (Nox)
  • Particulate matter (PM)
  • Carbon soot ( a by-product of diesel engine)

What is the process of making motor vehicle a BS6 compliant?

The process will involve thorough engine work and after combustion treatment. It includes enhanced combustion chamber design, and fuel injector design will ultimately improve the fuel-burning process and will result in finer atomization of the fuel. After combustion treatment includes the trapping of pollutants like Particulate Matter (PM), Nitrogen oxides (Nox) with the help of exhaust treatment systems.

Particulate filters are used in Direct injection petrol and diesel engines to resude the particulate matter emission or soot exhaust into the atmosphere. Nitrogen oxide is one of the main pollutants which is emitted by diesel engines or compression ignition engines. So Nox will be trapped by using a Lean Nox Trap known as LNT or a Selective Catalytic Reduction known as SCR system.

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Difference between BS4 and BS6 emissions:

There is a major difference between BS4 and BS6 emissions. The differences are given below:

1). Nitrogen oxides

The level of Nox is down by 25 percent for the petrol engines and a drastic 68 percent for the diesel engines. For petrols BS4 NOx limit was 80mg/km and in BS6 NOx limit is 60. That’s a 25 percent reduction. For diesels BS4 NOx limit was 250mg/km and in BS6 NOx limit is 80mg/km. That’s a  drastic 68 percent change.

2). PM levels

There will be a 82 percent reduction in PM levels under BS6 norms. PM limit under BS6 for petrols is 4.5mg/km (that too for gasoline direct injection engines only). For diesels BS4 PM limit was 25mg/km and in BS6 its 4.5mg/km.

3). Hydrocarbons

Only diesel will see a reduction in HC. The BS4 limit for HC+NOx was 300mg/km and now in BS6 it is 170mg/km. That’s a 43 percent reduction.

So is there any impact on fuel efficiency and performance of the vehicle with BS6?

The automakers were in a difficult situation before making BS6 engines. Now almost all car and bike manufacturers have made a BS6 compliant engines for their cars. So BS6 has made an effect on performance and fuel efficiency figures of vehicles. The power figures have somewhat been lowered by a mere 1 or 2 hp. Though the difference is not vast. Only on paper it may seem different but actually it’s a very small difference that is negligible in terms of real world driving conditions.

Is it the right time to buy a BS4 car or bike or should I purchase a BS6 vehicle?

The choice is completely yours. Neither you nor your vehicle will affect after 1st April 2020. It’s the date when BS4 vehicles will not be allowed to attract customers. You can buy a BS4 vehicle now as the car and bike manufacturers are offering heavy discounts on their BS4 models to clear out the BS4 stock as before as possible. Your vehicle will continue to run till the last date in registration certificate. BS4 vehicles purchased till 31st march 2020 will not get affect on 1st april 2020. So it’s the  right time to buy a BS4 vehicle. Also it’s up to you if you want a cleaner and greener BS6 vehicle. The cost of BS6 vehicles is much more than their BS4 models. So its just up to you.

Also adding that around 60 percent of the fuel station in India has been upgraded to BS6 grade fuel. So no need to worry about your BS4 vehicle. The BS4 vehicle is compatible with BS6 grade fuel and it won’t harm the engine. BS6 grade fuel, both petrol and diesel are just limited to 10mg/kg of sulphur content as compared to the 50mg/kg content in BS4 petrol and diesel. In BS4 grade fuel and BS6  grade fuel the only difference is the sulphur content. Lesser the content of sulphuer, cleaner the burning of fuel.

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This was the comparison and the adaptation of BS6 emission norms while the auto industry is slowly migrating and moving towards electric vehicles. For this, the main need is the infrastructure and other important needs. The industry yet still needs some time to migrate completely towards electric vehicle. Though the process has already been started and Evs are started coming to the market. Although we would suggest you buying BS VI vehicle as they will run more clean. They are a bit costlier at their initial stage but when the industry will evolve towards Evs, the price is expected to come down.

Also see Hybrid Vehicles, their advantages and disadvantages.

Written by Admin

Young, talented and a pure mechanical engineer. The founder of blog 'Be Curious'. The aim is to travel whole world with family members and friends. Solves all problems with to do attitude with positive thinking.