The Impact of Global Regulations On Current Engine Design & Technology

The global diesel engine design industry is going through a fundamental revolution. Since air pollution is one of the largest global concerns, the environmental emission regulations have become more stringent. The international commitments to reduce greenhouse gas emissions are making it important for engine manufacturers to bring major changes to how automotive and marine engines are designed, tested, and deployed.

India is also aiming to curb harmful emissions such as nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter (PM) caused by traditional engines. This also includes fuel choices, combustion strategies, and after-treatment technologies.

This article explores the national and global regulations and the steps manufacturers are taking on emissions regulations:

Historical Context of Engine Regulations

Diesel engines are designed to provide high power, efficiency, and durability. Thus, throughout the 20th century, they have been adopted in various industries, including:

• Shipping,
• Railways,
• Construction, and
• Heavy-duty road transport

However, the conventional engines left a strong environmental footprint, particularly in terms of NOx, SOx, PM, and CO₂ emissions.

In the marine sector, uncontrolled emissions from two-stroke diesel engines contributed significantly to coastal air pollution. Similarly, diesel road transport became a major source of urban PM and NOx.

Data suggests that CO₂ growth has accelerated sharply from 0.8 ppm/year in the 1960s to 1.6 ppm in the 1980s, 1.5 ppm in the 1990s, and now about 2.6 ppm/year (2015–2024). This shows the urgency of regulatory interventions that started in the late 20th century.

To limit emissions at source and drive technology upgrades, regulatory frameworks were created, such as

• MARPOL Annex VI for shipping
• Euro/US EPA Tier standards for road and non-road applications
• BS VI in India

Key Global Regulatory Frameworks

1. International Maritime Organization (IMO)

To set limits on SOx, NOx, and particulate emissions from ships, the International Maritime Organization enforced MARPOL Annex VI. The 2020 global sulfur cap permissible sulfur content in marine fuels was reduced to 0.5% m/m from 3.5%. At present, ships operating in Emission Control Areas (ECAs) should have advanced emission control systems to comply with Tier III NOx standards.

2. European Union (EU) Standards

The EU has led to regulatory tightening for land-based engines. Euro VI (road vehicles) and Stage V (non-road mobile machinery) impose strict NOx and PM limits. This has made it mandatory for manufacturers to adapt advanced diesel engine technology and features, such as:

• Diesel particulate filters (DPFs),
• Selective catalytic reduction (SCR) systems, and
• Advanced fuel injection technologies.

3. US EPA Standards

The US Environmental Protection Agency (EPA) sets Tier 4 Final standards for non-road diesel engines and similar heavy-duty regulations for on-road vehicles. These have dramatically reduced PM and NOx emissions over the past decade.

How is India Controlling Automotive Emissions?

India has also taken a significant step by leapfrogging from BS IV to BS VI in 2020 The emission standard is similar to Euro VI standards. Bharat Stage VI (BS VI) has focused on ultra-low sulfur diesel, advanced after-treatment, and tighter emission limits. However, this has made compliance a technical challenge to diesel engine design for manufacturers.

Recent Indian Draft Amendments (June 2025)

India is actively driving engine manufacturers and consumers to adapt to diverse fields and alternative energy sources. For that, they have made amendments to the existing compliances:

• Fuel Labeling & Technical Corrections—G.S.R. 431(E): This expands fuel categorizations to include “E85 or more,” updates biodiesel limits to “B100,” and corrects technical terms in regulatory tables. This ensures accuracy in fuel classification and compatibility with evolving engine designs.
• Hydrogen Vehicle Identification—G.S.R. 417(E): Introduces color-coded registration plates for hydrogen-fueled vehicles, distinguishing private, commercial, and rental categories. While not directly impacting tailpipe emissions, it demonstrates regulatory backing for alternative fuel mobility.

 

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Challenges in Diesel Engine Emissions

When diesel is combusted, it causes several emissions:

• NOx is formed at high combustion temperatures, linked to smog and respiratory issues.
• SOx originates from sulfur in fuel; a major contributor to acid rain.
• Particulate Matter (PM) are fine particles that cause severe health impacts.
• CO₂ is a greenhouse gas that is directly tied to climate change.

While for road transportation, adapting to newer types of fuel is easier, for marine engines, it seems to differ. Since vessels stay on the ocean for a long period, they have relied on heavy fuel oil.

Technological Innovations in Engine Design

Regulatory pressure has accelerated technological advancements in diesel engine design and after-treatment systems:

1. Engine Design Improvements

• Turbocharging & Miller cycle: Enhance efficiency and reduce NOx.
• Advanced Fuel Injection Systems: Precise fuel atomization reduces PM and improves combustion efficiency.
• Exhaust Gas Recirculation (EGR): Reduces combustion temperatures to limit NOx formation.

2. After-Treatment Systems

• Selective Catalytic Reduction (SCR): Converts NOx into harmless nitrogen and water using urea.
• Diesel Particulate Filters (DPFs): Trap and oxidize particulate matter.
• Diesel Oxidation Catalysts (DOCs): Reduce carbon monoxide (CO) and unburned hydrocarbons.

3. Alternative Fuels & Hybridization

• Liquefied Natural Gas (LNG): Lower SOx and PM emissions compared to conventional fuels.
• Biodiesel & Synthetic Fuels: Reduce lifecycle CO₂ emissions.
• Methanol & Ammonia: Emerging zero-carbon fuels under pilot projects.
• Hybrid-electric propulsion: Increasingly viable for short-sea shipping and urban buses.

What is the future outlook of engine design?

Data suggest that the trajectory of global engine emission regulations is toward carbon neutrality. For instance:

• IMO 2050 Strategy targets to reduce greenhouse gas emissions from international shipping by 50% in 2050 from 2008 levels.
• The EU Green Deal, on the other hand, aims for net-zero emissions by 2050, focusing on transport decarbonization as a priority.
• While hydrogen & fuel cells are currently at an early stage, they are expected to be adopted in heavy-duty applications and pilot shipping projects in the future years.
• With AI-driven control systems emerging, it is expected to optimize combustion and comply with the emission regulations.

Closing Thoughts

Engines, be it for cars, buses, heavy machines or marine vessels, play an important role in the global economy and day-to-day lives. However, with the strong environmental regulations, engine manufacturers must refine engine design and technology to comply with the frameworks.

The global and national regulatory frameworks are urging manufacturers to adopt cleaner fuels, smarter combustion, and advanced after-treatment systems. While there are still challenges remaining, especially in the marine and heavy-duty sectors, manufacturers like Weichai India have gradually started to adapt to the new regulations. We manufacture engines that are compliant with BS VI to take a step toward reducing air pollution.

FAQs

Q.1. Why are marine engines harder to decarbonize than road vehicles?

Large marine vessels need more energy output. And since they operate for long durations at sea, making fuel switching and retrofitting more complex compared to road vehicles. Therefore, they mostly rely on heavy fuel, like diesel.

Q.2. Which engine pollutes more, diesel or petrol?

Diesel engines emit higher levels of nitrogen oxides (NOx) and particulate matter (PM) compared to petrol engines, making them more harmful for air quality and public health. However, petrol engines generally emit more CO₂ per unit of energy, which contributes directly to climate change.

Q.3. Is diesel really bad for the environment?

Yes. While diesel engines are efficient and durable, their combustion produces NOx, SOx, particulate matter, and CO₂. These pollutants cause smog, acid rain, respiratory illnesses, and global warming. Marine diesel engines running on heavy fuel oil have historically been especially damaging, contributing significantly to coastal and urban air pollution.

Q.4. How can you reduce engine pollution?

There are quite a few ways. For instance, you can switch to an engine that complies with BS VI. Having after-treatment systems like SCR, DPFs, and DOCs reduces the amount of harmful gas and particulate matter being released into the environment.