www.chinabuses.org:  China bus builders experienced so much during the transformation from national standard Ⅱ to Ⅲ and that means a ordeal for bus and engine builders. The key factor is fuel injection system from standard Ⅱ to Ⅲ while the after-treatment technology of engine emission has to be applied from standard Ⅲ to Ⅳ.

With the implementation of national standard Ⅳ in some big cities, various mainstream engine companies launched the plan of products in accordance with standard Ⅳ. There have been 118 Ⅳ engine types with existing prototypes, including 105 diesel one ( 101 ones in line SCR, 4 ones in line EGR) and 13 natural gas engines.

At present, SCR becomes the mainstream of the national standard Ⅳ technology line. The upgrading of EGR engines to standard Ⅳ required big change of engine body while it is comparatively convenient for SCR. The current mainstream diesel power has confirmed SCR.

The layout of after-treatment system will make certain difficulty to the manufacturing of complete vehicle and chassis, the special charge door charge door or maintenance door for urea tank are required to be equipped and the suppliers of the aftertreatment system have to be designated based on engine, since the control of engine electric control system.

The big range growth of cost will lead to the more purchasing before implementation of regulation due to national standard Ⅳ, also some components will be bottleneck of sales for chassis even complete vehicle builders. It is good time for transformation for medium or small bus manufacturers.

It is possible that national standard Ⅲ and Ⅳ coexist for a long time. The new standard will offer new opportunity for natural gas engines because of far much lower cost to comply with standard than diesel engines.