What is Difference between BS4 and BS6 vehicles.

Difference between BSIV & BSVI Engine: BS4, BS6 Performance

To fight with the increasing pollution in INDIA. INDIA government has put (BSES) regulations known as Bharat Stage Emission Standards. This is mandated by INDIAN government that vehicles manufacturers have to meet BS VI standard in order to sell in market. These emission standards are applied to both Two wheeler and Four wheeler. The deadline for these standards to came in effect is 1 April 2020.
In this article, you will learn about differences between BS4 vs BS6 engine.

What is (BS4 or BSIV)?

It is necessary that we know about BSIV before studying about BS6 emission or BS6 compliant engine.

There is a governing organization for emissions from all types of vehicles in the country known as BSES, This organization introduced the first emission norms ‘India 2000’ in the year 2000. Two more standards are introduced called BS2 and BS3 in 2005 and 2010. Then in 2017 BS4 norms came into effect with stricter emission standards or norms.

As the regulations mentioned or set by the organization included changes like tailpipe emissions, Electronic Control Unit (ECU), ignition control, etc. The most important change introduced in BS4 is AHO (Automatic Headlamp On), This is set to improve the safety standards of two wheeler in INDIA.

What is BS6 (BSVI)?

BSES regulates the emission of pollutants from vehicles in the country. The Central Pollution Control Board which falls under the Ministry of Environment, Forest and Climate Change sets the standards to regulate emissions from vehicles in India.

This organization introduced the first emission norms ‘India 2000’ in the year 2000. Two more standards are introduced called BS2 and BS3 in 2005 and 2010. Then in 2017 BS4 norms came into effect with stricter emission standards or norms.

The BS6 emission standard is the sixth iteration of the emission norm and comparatively, it’s a big jump in terms of reducing pollution as compared to the current ongoing BS4. The gap is obvious as 1 standard is skipped this time, BS5 (BSV) has been skipped. This is done to control the emission more vastly as if we will go for BS5 then up to BS6 it will be very late to manage with the emissions.

BS4 (BSIV) and BS6 (BSVI) Difference:

These both emission norms set the maximum permissible levels for pollutants emitting from a car or a two-wheeler. BS6 emission standards are very stricter in comparison with BS4. These standards are the biggest change comes in the form of stricter permissible emission norms.

The below table compares the emission levels of BS4 and BS6 vehicles:

Fuel Type Pollutant Gases BS6 (BSVI) BS4 (BSIV)
  Nitrogen Oxide (NOx) Limit 60mg 80mg
Petrol Passenger Vehicle Particulate Matter (PM) Limit 4.5mg/km 250mg
  Nitrogen Oxide (NOx) Limit 80mg 300mg
Diesel Passenger Vehicle Particulate Matter (PM) Limit 4.5mg/km 25mg
  HC + NOx 170mg/km 300mg
environment friendly

What are BSI, BSII, BSIII, BSIV and BSVI Emission Norms?

These are emission standards set by the Bharat Safety Emission Standard (BSEB) to regulate the output of pollutants from vehicles plying on the road. The Central Pollution Control Board, under the Ministry of Environment and Forest and Climate Change, sets the permissible pollution levels and timeline to implement the same by vehicle manufacturers. 

The abbreviation of ‘BS’ is Bharat Stage and is suffixed with the iteration of the particular emission norms. The Indian emissions standards are based on the lines of European norms commonly known as EURO 2, EURO 3, and so on. The first regulations with the moniker India 2000 were introduced in 2000, with the second and third iteration introduced in 2001 and 2005 with the moniker BSII (BS2) and BSIII (BS3), respectively.

The fourth iteration BSIV or BS4 was introduced in 2017 and the delay between the introduction of BS3 and BS4 resulted in fast-tracking the BSVI or BS6 emission instead of BSV or BS5 norms. Each of these emission norms has stricter emission standards compared to its predecessors.

The table below offers an insight into the implementation timelines of the emission norms:

Emission Standard Reference Year of Introduction
India 2000 EURO 1 2000
Bharat Stage II (BS2) EURO 2 2005
Bharat Stage III (BS3) EURO 3 2010
Bharat Stage IV (BS4) EURO 4 2017
Bharat Stage V (BS5) EURO 5 skipped
Bharat Stage VI (BS6) EURO 6 2020

Impact of BS6 on CNG Cars:

Vehicle manufacturers will have to make minor changes or modifications to their diesel and petrol engines for the usage of CNG on BS6 vehicles. It’s only a matter of time before manufacturers start offering CNG compliant BS6 engines in the country. CNG powered BS6 cars or vehicles could be a stop-gap arrangement before the era of electric and hybrid vehicles are sold in the country.

How Do BS6 (BSVI) Diesel Engines Work?

The Selective Catalytic Reduction (SCR) unit converts nitrogen oxide (NOx) into diatomic nitrogen and water (both are harmless products) with the help of a catalyst. The SCR unit uses AdBlue or diesel exhaust fluid to reduce NOx emissions. This fluid is made up of two parts – urea and deionized water. When exhaust gases come in contact with the AdBlue fluid, urea is converted to ammonia and carbon dioxide and in turn, the ammonia converts NOx into nitrogen and water vapour, thereby reducing pollutants.

The AdBlue will be filled in a 10-litre capacity tank in smaller passenger vehicles. Currently, AdBlue is being sold by distributors at a premium rate; however, with the rapid increase in sales of BS6 diesel engines, the cost of AdBlue is expected to decline.

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