Although the National III emission standards were quickly implemented in Beijing, their nationwide adoption is expected to take until next year. For the development teams of major domestic diesel engine manufacturers, however, the State III standard is already behind them, as they have started preparing for the EU IV and Euro V standards. Two years ago, we were still questioning whether manufacturers were ready for the heavy-duty vehicle National II standard that was introduced at the end of 2004.
We must acknowledge that China is accelerating its upgrades in vehicle emissions, and the gap with international advanced levels is shrinking. However, as the gap between Chinese emission control technologies and foreign counterparts narrows, some previously hidden weaknesses are becoming more evident. The average level of China’s economic development still lags behind Europe, yet the rate of emission reduction is much faster. With varying population densities and environmental pressures across different regions, and an unevenly developed economy—especially with large cities and underdeveloped rural areas—it is difficult to apply a one-size-fits-all policy on vehicle emissions. Therefore, tailoring policies to regional differences is a realistic approach that aligns with national conditions, but it also poses greater challenges for engine manufacturers in terms of technological adaptability.
According to industry insiders, domestic diesel engine companies should develop a unified plan for technology upgrades once vehicles meet the National III standard. Previously, each engine factory handled emissions independently, but for Euro IV and beyond, collaboration among companies is essential.
For diesel engines, Euro IV marks a key technological turning point. Previously, internal cleaning technologies could meet emission standards, but from Euro IV onward, external post-treatment devices are required. Choosing the right technical route for these devices is a practical challenge for domestic manufacturers.
Currently, two main international routes are used to meet Euro IV standards: EGR (exhaust gas recirculation plus post-treatment) or SCR (selective catalytic reduction). Among these, SCR is the fastest way to achieve Euro V and a necessary step toward Euro VI. Engines using SCR can effectively reduce harmful nitrogen oxides and offer energy-saving benefits. However, implementing SCR requires infrastructure development, such as urea solution supply stations at gas stations. Although SCR may not be needed for Euro IV, the issue will become unavoidable in the future.
Lin Zhiqiang, a technical expert at Yuchai Technology Center, stated: “Yuchai isn’t worried about this. The related infrastructure and urea solution can bring significant economic benefits and drive the development of related industries. People will do it, and the government will support it if all diesel engine manufacturers agree that late construction is better than early.â€
If the goal is to accelerate emissions upgrades without unnecessary detours, then SCR is a viable shortcut.
Another important condition for meeting Euro IV and above is the availability of low-sulfur diesel fuel. This is very different from China’s current situation. Domestic oil companies promise to provide fuel meeting the National II standard with sulfur content below 500ppm, but Euro IV requires sulfur content below 50ppm—a big challenge for domestic refining companies.
Experts say that while refining technology is sufficient, ensuring nationwide compliance would involve high costs, especially due to high-sulfur crude oil in some regions and limited access to low-sulfur crude globally. As a result, only a few major cities like Beijing and Shanghai may enjoy high-quality fuel. For city buses, this is manageable, but long-haul trucks and buses face compatibility issues with varying fuel quality.
Professor Liu Zhongchang from Jilin University explained: “High-sulfur fuels don’t significantly affect engine performance and may even have a lubricating effect, but they impact emissions by poisoning catalytic converters.â€
In response to national conditions, companies are seeking solutions. Lin Zhiqiang said: “When selecting post-treatment equipment, we asked foreign suppliers to ensure their products can handle China’s high-sulfur fuel.â€
China’s emissions standards have evolved from scratch, catching up over time. Domestic engine companies have accumulated considerable experience and developed their own systems. Liu Zhongchang noted: “Although Euro IV standards are strict, and influenced by technology routes and fuel quality, compared to the initial implementation of State I and II standards, domestic companies now face fewer difficulties in meeting Euro IV.â€
Experts believe that as China gradually tightens vehicle emissions, it gives enterprises enough time to prepare, and companies will eventually develop low-emission engines suitable for their national conditions.
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