What is the difference between bs4 and bs6 engine?

The primary difference between BS4 and BS6 engines lies in their emission standards and technology. BS4 (Bharat Stage 4) norms, implemented in 2017, set limits on pollutants like carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM). BS6 (Bharat Stage 6), which came into effect in April 2020, is a much stricter standard aimed at reducing vehicular pollution significantly. Compared to BS4, BS6 engines produce nearly 60-70% lower NOx emissions in diesel engines and about 25% less in petrol engines. BS6 engines also require advanced components such as diesel particulate filters (DPF) and selective catalytic reduction (SCR) systems, along with upgraded fuel injection technology. Additionally, BS6 fuel itself has a lower sulfur content (10 ppm vs. 50 ppm in BS4), which helps keep emissions in check and ensures proper functioning of these advanced engines. This makes BS6 vehicles not only cleaner for the environment but also slightly more complex and expensive due to the upgraded technology.

Understanding BS4 and BS6 Emission Norms

Bharat Stage Emission Standards are emission regulations instituted by the Government of India to control air pollutants from internal combustion engine equipment, including motor vehicles. These standards are broadly based on European regulations.

• BS4 (Bharat Stage IV) norms came into effect across India in April 2017. They required vehicles to comply with stricter emission standards than BS3, reducing harmful pollutants like NOx, CO, and PM.
   
• BS6 (Bharat Stage VI) norms were implemented nationwide from April 1, 2020. Interestingly, India skipped BS5 altogether to directly adopt BS6, matching Euro 6 standards in many aspects. This brought India almost at par with European emission standards.

The key goal of BS6 was to drastically cut down emissions of harmful pollutants and promote cleaner air.

Key Differences Between BS4 and BS6 Engines

The jump from BS4 to BS6 was not just incremental — it was transformative. Here’s how they differ:

Technical Specifications: BS4 vs BS6 Engines

BS6 engines involve multiple technological upgrades compared to BS4. Some of these include:

• Engine calibration & ECU mapping: BS6 engines require advanced calibration to meet stricter norms.
• Advanced catalytic converters: New catalytic converters reduce pollutants more efficiently.
• Diesel Particulate Filters (DPF): Especially in diesel vehicles, to trap fine particulate matter.
• Selective Catalytic Reduction (SCR): Technology using AdBlue (urea solution) to cut NOx emissions.
• On-Board Diagnostics: Standard OBD-II systems help monitor emissions in real-time.
   

Meanwhile, BS4 engines were simpler and lacked many of these advanced components, which made them cheaper but also more polluting.

Can a BS4 Vehicle Be Upgraded to BS6?

This is one of the most common questions. Unfortunately:

• No, you cannot practically upgrade a BS4 vehicle to BS6.

This is because BS6 compliance is not just about changing a few parts — it involves a complete overhaul of the engine, exhaust system, and electronic controls. Retrofitting DPF or SCR systems into BS4 vehicles is technically challenging and economically unviable.

However, using BS6 fuel (low sulphur) in BS4 vehicles is safe and can marginally reduce emissions, but it does not convert the vehicle into a BS6-compliant machine.

Pros and Cons of BS4 and BS6 Engines

Pros of BS6 Engines

• Much cleaner emissions (up to 70% less NOx in diesels).
• Contribute to improved air quality.
• Equipped with advanced technologies like OBD, DPF, SCR.
• Future-ready for stricter norms.
   

Cons of BS6 Engines

• Higher cost of vehicles (10-15% more).
• Slightly higher maintenance in diesel due to DPF regeneration needs.
• AdBlue refilling required in diesel SCR systems.
   

Pros of BS4 Engines

• Lower purchase cost.
• Simpler technology, easier maintenance.
   

Cons of BS4 Engines

• Significantly higher emissions.
• Phased out; resale value likely to drop faster.
• Not compliant with current environmental standards.
   

The transition from BS4 to BS6 is a landmark move in India’s fight against air pollution. While BS4 engines were simpler and cheaper, BS6 engines are far more environmentally friendly, leveraging modern emission control technologies. Though the initial costs are higher, the long-term benefits to health and the environment make BS6 engines a crucial step forward.

FAQs on BS4 vs BS6 Engines

1. Can I still buy a new BS4 car?

No. As of April 2020, all new vehicles sold in India must comply with BS6 norms. Only BS6 vehicles can be registered.

2. Will BS6 fuel damage my BS4 vehicle?

No. BS6 fuel (with lower sulphur) is actually better for BS4 engines and can slightly reduce particulate emissions.

3. Are BS6 vehicles less powerful?

Initially, some BS6 models had slight power drops due to emission control. But manufacturers have optimized engines, so most BS6 vehicles perform as well as their BS4 counterparts.

4. Do BS6 diesel cars need AdBlue?

Yes, most BS6 diesel vehicles use AdBlue to run SCR systems, which reduce NOx emissions.