What Is Difference Between BS3 and BS4 Engine Bikes.

What Is Difference Between BS3 and BS4 Engine Bikes.

BS Stands For Bharat Stage- 1,2 ,3,4 
BS is related with air pollution control norms set by Indian Government . Indian Government has decided allowable limit in percentages for various exhaust gases  like Carbon Dioxide, Hydrocarbon, Carbon Monoxides. This emission gases hazardous to the environment.
  All new vehicles manufactured after the implementation of the norms have to be compliant with the regulations.

What Is BS ?

Bharat stage emission standards are emission standards instituted by the Government of India to regulate the output of air pollutants from internal combustion engines and Spark ignition engines equipment, including motor vehicles. The standards and the timeline for implementation are set by the Central Pollution Control Board under the Ministry of Environment & Forests and climate change.
First BS-III rule was introduced in 2005 and was implemented in 15 cities overall and by 2010 the nationwide implementation of BS-III vehicles was completed.
BS-IV for 13 metro cities was introduced in April 2010 and the nationwide implementation is also now completed wit Supreme Court banning the sale of all BS-III vehicles starting April 1, 2017.
Bs4 means a ‘ catalytic converter’ is a mandatory addition to the exhaust system 
The nation wide roll out of BS-IV suffered a delay due to lack of availability of BS-IV compliant fuel. Oil makers had to make the necessary investment to manufacture 50 ppm ultra low sulfur required to support BS-IV norms.
Also, the BS norms are based on European emission norms which, for example, are referred to in a similar manner like ‘Euro 4’ and ‘Euro 6’. These norms are followed largely by all automakers across the globe and act as a good reference point as to how much does a vehicle pollute.
To wrap it up and put it simply, Bharat Stage emission norms are largely similar to the European emission norms followed globally.
Why BS 4 Applicable strictly 
India has some of the most polluted cities in the world and automobiles are often considered as one of the biggest factors responsible for it. The need of the hour is to control the pollution levels by all means possible and since globally, countries are implying Euro 6 levels of emission regulations, India needs to step up its game and hence the BS III to BS IV emission norm implication.

Difference between BS3 And BS4 / BS4 bike Changes ?

You might wonder what exactly changes in engine and exhaust system should be made to meet emission gases requirement as per bs4.
  • Bs4 cars require special bs4 compliant Bs4 diesel( containing low sulfer i.e.50ppm) , while Bs3 cars can run on high sulfer (500 ppm) containing bs3 complaint or bs4 complaint diesel.
  • Difference in emissions b/w bs3 and bs4


carbonmonoxide 2.30 g/km 

HC 0.20 g/km 

NOX 0.15 g/kmBS4 

carbonmonoxide 1.00 g/km 

HC 0.10 g/km 
NOX 0.08g/km

These figures clearly state that BS IV engines would cut down emissions by 80% and hats off to authorities who have taken this bold step for a better environment

  • Major change in BS IV is the evaporative emission control. In 2 wheelers, in order to comply with the norms, bikes will have to be fitted with carbon canisters to control evaporative emissions. The vapour from fuel has a higher amount of unburned hydrocarbons (extremely harmful to environment). So when the vehicle is parked, these vapours are formed. These escape out when refuelling and this has to be limited according to BSIV norms.
  • The commercial vehicles are mandated to have EGR and SCR as per BS IV norms. Selective catalytic reduction (SCR) converts NOx molecules into Nitrogen and water.

Sachin Thorat

Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.

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