What is BS6 (BSVI). What is the difference between bs4 and bs6 engine : BS6 engine working

 To regulate the pollution emitted by cars and two-wheeler s, the govt of India has put forth regulations referred to as Bharat Stage Emission Standards (BSES). The Central government has mandated that each one vehicle manufacturers, both two-wheelers and four-wheelers, should manufacture, sell and register only BS6 (BSVI) vehicles from 1 April 2020.

In this article, you'll study BS4 vs BS6 engine, major differences and performance of the new BS6 engine.
Need for NOx regulation

What is BS6 (BSVI)?

The governing body, Bharat Stage Emission Standards (BSES), regulates the output of pollutants from vehicles plying 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.

The first emission standard or norm, introduced in the year 2000, was known as ‘India 2000’ and later, BS2 and BS3 were introduced in 2005 and 2010, respectively. While the first three emission norms were introduced at regular intervals, BS4 was introduced in 2017, after a gap of seven years.

The BS6 emission standard is the sixth iteration of the emission norm and comparatively, it’s a substantial leap in terms of reducing pollution compared to the outgoing BS4. This is also because the BS5 (BSV) has been skipped in an effort to move to better emission norms.

BSVI legislation

· World harmonized test  cycle
· Emission limit: NOx;
· PM, PN, CO & HC
· Useful life
· requirements
· In-service conformity/  in- use emissions
· Certification,  conformity &  enforcement
· On-Board
· Diagnostics
NOx control  monitoring

What is BS4 (BSIV)?

Before we understand about BS6 emission or BS6 compliant engine, let’s understand the current BS4 (BSIV) emission norms, engine, performance, and its significance. The BSES, which is the governing organization for emissions from all types of vehicles in the country, introduced the first emission norms with the name ‘India 2000’ in the year 2000. 

Difference Between BS4 and BS6

Both BSIV and BSVI are emission norms that set the maximum permissible levels for pollutants emitting from a car or a two-wheeler exhaust. Compared to the BS4, BS6 emission standards are stricter. While manufacturers use this change to update their vehicles with new features and safety standards, the biggest or the significant change comes in the form of stricter permissible emission norms.
The below table offers an insight into the change in the permissible emission levels of BS6 vehicles compared to BS4 vehicles:
Fuel Type
Pollutant Gases
Petrol Passenger Vehicle
Nitrogen Oxide (NOx) Limit
Particulate Matter (PM) Limit
Diesel Passenger Vehicle
Nitrogen Oxide (NOx) Limit
Particulate Matter (PM) Limit
HC + NOx

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

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

These are emission standards set by the governing body 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 2EURO 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
Year of Introduction
India 2000
Bharat Stage II (BS2)
Bharat Stage III (BS3)
Bharat Stage IV (BS4)
Bharat Stage V (BS5)
To be skipped
Bharat Stage VI (BS6)

BS VI – Steady state cycle

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

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.

BS norms trend – PM vs. NOx  SCR (or) EGR + SCR for BS VI

BS norms trend – PM vs. NOx  SCR (or) EGR + SCR for BS VI

List of BS6 Cars Available in India 2020:

Ahead of the deadline of the implementation of BS6 compliant vehicles from 1 April 2020, several car and bike manufacturers have launched BS6 cars and bikes in India. Below is the list of BS6 cars and two-wheeler currently available to buy:

BS6 Sedan Cars:
Maruti Suzuki Dzire
Hyundai Elantra
Mercedes Benz E-Class
Audi A6
BS6 Hatchback Cars:
Maruti Suzuki Alto 800
Maruti Suzuki S-Presso
Hyundai Grand i10 Nios
Maruti Suzuki Swift
Maruti Suzuki Wagon R 1.2-litre
Maruti Suzuki Baleno
Toyota Glanza
Kia Seltos
Jeep Compass
BS6 MPV Cars:
Maruti Suzuki Ertiga
Maruti Suzuki XL6
BS6 Crossover Cars:
Maruti Suzuki XL6
Maruti SuzukFINi S-Presso

List of BS6 Bikes/Two-Wheelers in India 2019:

Here is the list of BSVI bikes in India that has been launched much before the deadline of 1 April 2020:
· BS6 Scooters:
Honda Activa 125
· BS6 Two-Wheelers:
Hero Splendor iSmart 110
Honda SP 125
Yamaha FZ V 3.0
Yamaha FZ S V 3.0
Jawa Perak


                                ROYAL ENFIELD CLASSIC 350 BS6

2020 ROYAL ENFIELD CLASSIC 350 BS6 Sound | Safety | New Colors | Price Mileage Spec Review

Why are there no Light switch on BS4 Bikes?

All two-wheelers, including motorcycles and scooters that were manufactured from 1 April 2017 featured the Automatic Headlamp On (AHO). As the moniker suggests, all two-wheelers are required to have the headlights on at all times. In compliance with the BS4 norms, all new two-wheelers will not have a light switch for the headlight, since it needs to be always on. However, the pass and the low and high beam light switch were kept untouched.
The reason behind the introduction of AHO was keeping both the rider’s and pedestrian’s safety. The light remains on during the day as well, which makes it visible to passersby. 

FAQs About BS6 Vehicles:

Here are the frequently asked questions about BS6 cars and bikes in India:
FAQs About BS6 Vehicles:

What happens if you fill BS6 fuel in BS4 car?

You can fill BSVI fuel in BSIV cars or older models. Sulphur in fuel acts as a lubricant inside the engine and burns efficiently. The BSVI fuel has lesser sulphur; however, it contains additives which helps in the lubrication of the engine.

What’s next after BS6?

Currently, there are no new emission norms has been set by the governing body. However, there may be a second version of the BS6 which will include Real Driving Emissions (RDE) cycle. As per this law, the Automotive Research Association of India (ARAI) will test new vehicles in real-world conditions to ascertain the level of pollution. Currently, the test is done in a controlled environment.

Can BS6 engine run on BS4 fuel? Does it meet the BS6 emission standards?

The emission from the tailpipe of a BS6 vehicle should match the BS6 norms and this is possible only if BS6 fuel is filled in BS6 cars. While a BS6 car can run on BS4 fuel, it may not comply with the BS6 norms.

What will happen to BS4 vehicles after 2020?

No new BS4 vehicles will be manufactured or registered by the RTO after 1st April 2020 when the BS6 emission norms are implemented. However, existing BS4 vehicles will be allowed to run on public roads. Currently, there is no deadline set for BS4 vehicles to stop playing on public roads.

Is BS6 fuel expensive compared to a BS4 fuel?

Prior to the nationwide rollout of BS6 fuel, it has been implemented in Delhi and the NCR and the prices are not different between BS6 and BS4 fuel. However, this may change once it’s implemented across the country due to input costs incurred by the Oil Marketing Companies (OMCs) towards upgrading their facilities.

Can I convert my old car to meet BS6 emission norms on my own?

You can convert your old car to BS6 standards; however, it requires time and money. Also, it’s illegal.

DOC /DPF Catalyst functional  challenges

1)Diesel Oxidation Catalyst –
· Effective soot filter and reduce PN
· Secondary HC reduction
· Generate additional NO2 for  improving SCR NOx conversion
· Should have higher soot mass
· limit
· Low Back pressure

2)Diesel Particulate Filter–

· Oxidize HC and CO to reduce these  emissions in engine exhaust
· Oxidize NO to NOfor filter passive  regeneration and improving SCR NOx  conversion.
· Create exotherm through HC injection  to provide the temperature required for  filter active regeneration
· Allow low HC Slip during HC dosing
· Low Back pressure

What is the difference between a Euro 6 and a BS6 engine?

The emission limits for both the Euro 6 and BS6 engine are numerically equivalent, although it could be slightly tweaked to Indian standards.

What is the difference between BS4 and BS6 car performance?

The BSVI engine is relatively cleaner than the BSIV engine leading to lower combustion. Add new components to the exhaust system and it reduces the overall performance of the car to a certain extent, although not that significant. That said, vehicle manufacturers are developing engines which offer a balance between performance, efficiency and emissions.

What is the difference between BS4 and BS6 cars fuel economy?

The difference between BSIV and BSVI cars’ fuel efficiency is minimal. The BS6 Maruti Dzire has an ARAI certified fuel efficiency of 21.21 km/l while the outgoing BS4 Maruti Dzire returned a mileage of 22 km/l. A slight decline in mileage although not significant.

What are CAFE norms?

The Central government has proposed to introduce Corporate Average Fuel Efficiency (CAFE) in sync with the global auto industry. Under these norms, cars are expected to be 30% fuel efficient from 2022 and by the end of 2021, it’s expected to be increased by another 10%. Through CAFE norms, fuel efficiency will be decided on how many litres does a vehicle consume while running 100kms.

Why the skip from BS4 to BS6 and not BS5?

The first emission norm was introduced in 2000, while the second and third iteration was introduced in 2005 and 2010. The BS4 was implemented in 2017, the big gap prompted the government to skip BS5 and jump to BS6 in an effort to reduce pollution in the country.

Do BS4 vehicles require a pollution certificate?

Yes, all vehicles plying on Indian roads require Pollution Under Control (PUC) certificate as per the Motor Vehicle Act.

My Commitment


Besides regulations, we have the  moral responsibility to pass-on a safer  and cleaner planet to the Next  Generation !!!


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