Bus engine is different from the truck engine in environment protection, power efficiency and fuel consumption due to the different driving conditions and purposes. The city bus especially has stricter requirement for the gas emission because of short driving distance, low speed and high frequency of start and brake. On March 13, 2007, at the opening ceremony of Shanghai World Bus Exhibition, Yuchai, as the main enterprise of internal combustion engine, strongly expressed the tone of "king of power, and pioneer of environment protection".
As introduced by the director's senior technical advisory of Yuchai Machinery Co., Ltd, Dr. Liqin, Yuchai has well prepared for the bus engine market. The bus engine produced by Yuchai has many advantages such as low oil consumption, high ratio of performance and price, strong power, high quality, low emission, low noise, and good service. The YC6M series engines, for example, are favorable for the following reasons: first is on the fuel efficiency: fuel consumption of this series is 10 to 15% lower than the other domestic engines under the same power condition; the adoption of 24-valves technology greatly improves the air inlet and exhaust efficiency; the use of powerful Bosch pump achieves better atomization effect; the application of low inertia small bore middle P type injector matches better with the combustion chamber to makes more balanced mix and more adequate combustion; the design of flexible piston ring effectively lowers the lubricant consumption; the ratio of lubricant and fuel consumption is less than 0.1%, and no need to add lubricant in 10,000 kilometers under normal condition which greatly decreases the cost. Second is on the power efficiency: the displacement of this series reaches 10 liters; the biggest torque is 165N.m and the maximum power is 390 horse powers; the powerful low speed output torque makes the acceleration response faster. Third is on the cooperation with Europe AVL company, the injection system may bear 220bar explosive power in maximum, and the high tenacity design makes the machine more reliable. Fourth it completely reaches the National-2 and National-3 emission standard and has the potentiality to upgrade to National-4 standard. Fifth is that the series have optimized the gap between piston and cylinder so the slap sound of the piston is lower. The noise is 2-4 db lower than other equivalent domestic engines and is far less than the required 84db in driving according to the national standard. Sixth we provide warranty for 250,000 km or 20 month. We may change the whole machine in one month after sale since we have 31 offices and 1168 service stations around the country. The service radius is less than 40 kilometers (expect for some border area). The service will be in place within 12 hours and the parts will be delivered in 24 hours. In general the clients will get the best guarantee with good service.
After 2 years of development, Yuchai Machine has the strong ability on controlling emission to protect environment. When China was still implementing Europe-2 standard in 2005, Yuchai had developed the 6L, 6G and 4G electric control diesel engines that met the Europe-3 standard and strongly impacted the Europe-3 engine market at that time. In the first half year of 2006, Yuchai successfully entered and stimulate the bus engine market in China. Yuchai Europe-3 engines in a short time were sold over Beijing, Guangzhou, Shenzhen, and Macao, where strictly practiced emission standard and occupied these important markets. Because of the Olympic Games in 2008, Beijing might implement the Europe-4 standard in advance. Huanghai bus and Xiamen King Long bus with the Cummins Europe-4 engines were already on the market. Yuchai developed Europe-4 engine after the successful marketing of Europe-3 engine which was closely kept with the pace. Jinghua buses with the Europe-4 engine from Yuchai will start to run in April or May this year after testing.
Dr. Liqin said: comparing with the biggest competitor Cummins, Yuchai adopted the German Benz technology which is more mature and has been tested by the market for 3 years. Yuchai's Europe-4 engine also mainly adopts the SCR (selective catalytic reduction) resolution which is more suitable for the domestic market because the sulphur content is too high in the fuel. Currently in China, more than 50% fuel is imported with the sulphur content of 350ppm. The oil consumption and fuel sensitivity are important factors to select technical solutions. The EGR system would put the developer into dilemmas of "low emission" or "low oil consumption". On the contrary, the SCR solution is better on the fuel efficiency. Repeated test results proved that there was no contradiction between lowering emission and decreasing oil consumption with the SCR system. The oil consumption is 5% lower than that of National-3 engines and the emission level is one fifth of the National-3. The emission of 5 National-4 engines equals the emission of one National-3 engine. Regarding the sensitivity of sulphur, SCR is the best system for post treatment of emission; while the CRT (continuous regenerating trap) technology is potentially unsafe. On one hand, the sulphur would be poisonous for the system, and on the other hand, the dust in the waste gas would block the trap that must be cleaned often. Theoretically, its hard to meet the Europe-5 or higher standard with the CRT technology.