Difference between BSIV & BSVI engine | BS4 vs BS6

The difference between BSIV & BSVI engine is not just technical but also environmental, economic, and regulatory. The ban on the sale of BS IV vehicles in India, effective from April 1, 2020, marked a significant transition to BS VI vehicles. Understanding BS4 vs BS6 is essential for car buyers, automobile enthusiasts, and even those simply concerned with India’s fight against air pollution. This detailed guide explains the changes in emission standards, the impact on diesel engines, and why BSVI engines are a leap forward for cleaner air.

Introduction to bharat stage emission standards

The Bharat Stage Emission Standards (BSES) are a set of stringent emission norms introduced by the Indian government to regulate the pollution emitted by motor vehicles. These standards aim to reduce harmful emissions and improve air quality across the country. Modeled after European emission standards, the BSES have been implemented in several stages, each introducing stricter emission standards to curb air pollutants. The two most recent stages, BS4 and BS6, represent significant advancements in emission control technologies and regulatory measures. By enforcing these norms, the Indian government seeks to mitigate the environmental impact of motor vehicles and promote a cleaner, healthier environment.

History of bharat stage

The history of Bharat Stage emission standards dates back to 2000 with the introduction of the first emission norm, known as India 2000. This was a pivotal step in regulating vehicle emissions in India. Following this, BS2 was introduced in 2005, BS3 in 2010, and BS4 in 2017, each stage progressively tightening the emission standards. The latest stage, BS6, was implemented in 2020, marking a significant leap in reducing pollution levels. These emission norms have been crucial in addressing the environmental impact of vehicles and improving air quality. The Indian government’s commitment to these standards reflects its dedication to reducing pollution and protecting public health.

What is BS4 (Bharat Stage IV)

BS4, or Bharat Stage IV, is an emission norm introduced in 2017 to regulate the emission of pollutants from vehicles. This norm sets limits on the emission of nitrogen oxide (NOx), particulate matter (PM), and carbon monoxide (CO). While BS4 was a significant step forward, it is less stringent compared to BS6. BS4 vehicles use diesel particulate filters (DPF) to reduce particulate matter emissions but do not employ selective catalytic reduction (SCR) technology, which is essential for reducing NOx emissions. As a result, BS4 allows for higher emission levels compared to BS6, making it less effective in combating air pollution.

What is BS6 (Bharat Stage VI)

BS6, or Bharat Stage VI, is the latest and most stringent emission norm introduced in India, effective from 2020. This norm significantly tightens the limits on pollutants such as NOx, PM, and CO. BS6 vehicles utilize advanced technologies like selective catalytic reduction (SCR) and diesel particulate filters (DPF) to minimize emissions. Additionally, BS6 mandates the use of ultra-low sulfur fuel, which drastically reduces sulfur dioxide (SO2) emissions and other harmful pollutants. These measures are designed to lower pollution levels and improve air quality, making BS6 a critical step towards a cleaner environment.

What are bharat stage emission standards?

The Bharat Stage emission standards are rules set by the Central Pollution Control Board (CPCB) under the Motor Vehicle Act to regulate the output of air pollutants from internal combustion engines and spark-ignition engines. These standards were first introduced in 2000 and have been periodically updated.

Each phase, such as BSIV (Bharat Stage IV) or BSVI (Bharat Stage VI), represents a significant step in limiting harmful vehicle emissions like nitrogen oxide, carbon monoxide, particulate matter, and carbon dioxide. These limits are aligned with international best practices, with BS6 emission norms closely resembling Euro 6 standards. BS6 fuel is necessary to meet the desired emission levels set by the new regulations.

Why did India jump from BS4 to BS6?

India skipped BS5 and moved directly from BS4 and BS6 norms to control rapidly worsening air quality. The reason was the urgent need to combat air pollutants that were affecting millions. The Indian government made it mandatory for all motor vehicles manufactured after April 1, 2020, to comply with BS6 emission norms.

This jump also allowed time for vehicle manufacturers to adopt advanced technologies and rethink engine design and fuel delivery systems.

Key differences between BSIV & BSVI engine | BS4 vs BS6

1. Emission standards and limits

The most obvious difference between BSIV & BSVI engine is the stricter emission standards in BS6. BS6 norms impose stricter emission limits compared to BS4, requiring manufacturers to adopt advanced technologies to meet these standards. BS6 significantly reduces nox emissions, which are a major contributor to air pollution.

Nitrogen Oxide (NOx) levels in petrol engines have been reduced by 25%, and in diesel engines by nearly 68%.

Particulate matter PM emissions in diesel cars are cut down by over 80%.

2. Use of selective catalytic reduction (SCR)

BS6 engines, especially in diesel vehicles, employ Selective Catalytic Reduction systems that use diesel exhaust fluid (DEF), like AdBlue, to convert harmful NOx emissions into harmless diatomic nitrogen and water.

These advanced technologies in BS6 diesel engines work by using SCR to convert nitrogen oxides into harmless substances, ensuring compliance with strict emission standards.

3. Introduction of diesel particulate filters (DPF)

To meet stricter emission standards, BS6 diesel passenger vehicles are equipped with diesel particulate filters. These trap and burn particulate matter, greatly reducing tailpipe emissions. The diesel particulate filter (DPF) is a necessary component introduced in the BS6 emission norms to reduce pollution levels from diesel vehicles.

4. Better fuel efficiency

BS6 vehicles are designed with improved fuel delivery systems and electronic control units (ECUs) that optimize combustion. While the technology is more complex, it generally leads to better fuel efficiency, although mileage may vary based on engine tuning.

The critical role of the fuel delivery system in maintaining performance and fuel efficiency cannot be overstated, as using the incorrect grade of fuel can lead to decreased fuel economy and increased emissions.

5. Cleaner fuel: BS6 Fuel vs BS4 Fuel

BS6 fuel contains just 10 ppm (parts per million) of sulphur concentration compared to 50 ppm in BS4 fuel. This ultra-low sulfur fuel supports advanced emission control technologies without damaging engine components.

BS4 engines utilize fuel containing real sulphur, which leads to higher emissions and pollutants, compared to the cleaner fuel used in BS6 engines.

Impact on petrol and diesel engines

Petrol engine

The difference between BSIV & BSVI engine is less dramatic in petrol vehicles, though emission cuts are still required. Improved catalytic converters and ECUs help reduce carbon monoxide, hydrocarbons, and nitrogen oxide.

Diesel engines

In diesel engines, changes are massive. The addition of SCR, DPF, and low-sulfur BS6 fuel is essential to meet the tough BSVI emission norms. These steps are necessary to curb harmful emissions that contribute to poor air quality. Exhaust gases interact with AdBlue in SCR systems, converting harmful nitrogen oxides (NOx) into harmless by-products like nitrogen and water, ultimately contributing to pollution reduction.

Cost implications for consumers

Cars with BSVI engines are costlier than BSIV models. The price increase is due to advanced components like diesel particulate filters, SCR units, and better sensors for real driving emission monitoring. However, the trade-off is lower emissions and improved health outcomes. The significant reduction in the allowable particulate matter limit under BS6 regulations has also contributed to the increased vehicle costs.

Effect on air pollution and health

The adoption of BS6 emission norms has a direct effect on reducing air pollutants like particulate matter, nitrogen oxide, and carbon monoxide. These pollutants have been linked to respiratory diseases, cardiovascular issues, and poor lung function, especially in children and the elderly.

The BS6 updates enforce stricter limits on nitrogen oxides (NOx) emissions from vehicles, implementing advanced technologies to drastically reduce permissible NOx levels compared to previous standards.

Challenges faced by car manufacturers

Car manufacturers faced major hurdles transitioning from BS4 to BS6. New engines had to be developed, tested under real driving emission conditions, and validated for durability and efficiency. Additionally, the introduction of the onboard diagnostic system as a significant feature for compliance with BS6 emission standards differentiated BS6 vehicles from their BS4 counterparts.

Further, the supply chain for BS6 fuel needed expansion across India. This required coordination between oil companies, regulatory bodies, and vehicle manufacturers.

Impact on two wheelers

Two wheelers, which dominate Indian roads, also saw significant changes. They now come equipped with electronic fuel injection systems instead of carburetors. This ensures better fuel efficiency and lower emissions.

Environmental impact

Shifting to BS6 emission norms is a crucial step towards meeting India’s commitment under the Paris Agreement. Lowering environmental carbon emissions from millions of motor vehicles will improve air quality and slow climate change.

The implementation of BS6 norms has prompted the automotive industry in India to adopt newer, cleaner technologies, resulting in reduced vehicle emissions, ultimately contributing to improved air quality and benefiting public health and the environment in the long term.

List of BS6 cars available in India

India’s automotive market has seen a surge in BS6-compliant vehicles, with major car manufacturers like Maruti Suzuki, Hyundai, and Tata Motors leading the way. Popular BS6 models include the Maruti Suzuki Swift, Hyundai Grand i10, and Tata Tiago. These cars are equipped with advanced technologies such as SCR and DPF to meet the stringent BS6 emission norms. The transition to BS6 has prompted car manufacturers to innovate and produce vehicles that are not only environmentally friendly but also fuel-efficient. As the demand for cleaner vehicles grows, the list of BS6 cars in India continues to expand, offering consumers more choices for sustainable transportation.

Summary table: BS4 vs BS6

Frequently asked questions (FAQ)

Q1: What is the difference between BSIV & BSVI engine?

A: The difference between BS4 and BS6 engines is significant in terms of emission standards and technologies used. BS6 engines produce significantly lower emission levels than BS4. They use technologies like Selective Catalytic Reduction, diesel particulate filters, and run on ultra low sulfur fuel.

Q2: Can BS6 vehicles run on BS4 fuel?

A: No, BS6 vehicles should only use BS6 fuel. Using BS4 fuel can damage BS6 engines and increase pollution emitted. BS6 fuel is specifically formulated to help regulate emissions to meet the stricter standards set by the Bharat Stage Emission Standards (BSES), significantly reducing the amount of pollutants vehicles can emit.

Q3: Are BS6 cars more expensive?

A: Yes, due to the addition of advanced emission control technologies and upgraded components designed to meet stringent emission standards.

Q4: How does BS6 help improve air quality?

A: By reducing NOx emissions, carbon monoxide, and particulate matter, BS6 norms help reduce emissions significantly compared to BS4 engines. This reduction in emissions leads to improved air quality and helps reduce diseases caused by air pollutants.

Q5: Is it worth upgrading to BS6 now?

A: Yes. BS6 vehicles are cleaner, fuel efficient, and compliant with current emission regulations. They help reduce NOx emissions through the use of advanced technologies like the Selective Catalytic Reduction (SCR) unit and AdBlue, a diesel exhaust fluid. This transition from BS4 to BS6 standards significantly decreases harmful pollutants, making the upgrade worthwhile.

Conclusion: Why BS6 is the future

The difference between BSIV & BSVI engine reflects more than just a technical upgrade—it’s about protecting lives, reducing harmful emissions, and building a sustainable future. As we move toward stricter emission standards, understanding BS4 vs BS6 is crucial for every consumer, policymaker, and manufacturer.

While the transition comes with challenges, the rewards—a cleaner sky, healthier lungs, and global environmental responsibility—make it worthwhile. Whether you drive a petrol engine scooter or a diesel passenger vehicle, choosing BS6 means choosing better.

BS6 emission norms are not just another set of rules—they’re the roadmap to a healthier, greener India.

ARN: Zuno/Blog/DM/Difference between BSIV & BSVI engine | BS4 vs BS6/04/25/11

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