Experimental Study On Bench Calibration For 4G69 Gasoline Engine

In recent years, with the rapid surge in automobile possessing capacity, automobile exhaust emissions and pollution is serious day by day, furthermore, the scarcity of resource in the world let automobile consumers bear great oil price pressure. Therefore, energy conservation and environmental protection have been the common focus of the manufacturers and the consumers, which means that the automobile companies must change the growth mode from extensive to intensive, accurate, economical type. In the future, energy conservation, consumption reduction, emission reduction will be the new standard in the automobile industry, the new threshold.In the trend of automobile energy conservation,in order to meet increasingly stringent emissions and fuel consumption regulations, Geely Automobile Company decide to replace old engine in an SUV vehicle. Because the original 4G64-type engine applies single overhead camshaft, natural aspiration way, and the valve lift could not be changed, so it is hard to reach ideal distribution phase and optimal charge efficiency,and also improve fuel economy and power further. To this end, we develop 4G69 MIVEC gasoline engine to achieve to enhance engine power, improve fuel economy and emission characteristics, while meeting our current implementation emissions and fuel consumption regulations.The Mitsubishi MIVEC variable valve timing mechanism are elaborated. In the low-medium speed, the valve lift difference is used to strengthen the swirling of the mixture, and improve the mixing homogeneity of the mixture. The small valve overlap can decrease internal EGR rate and improve low-speed combustion stability, thus improve fuel consumption and reduce emissions. At the same time, the low valve lift can reduce friction loss and the scavenging volume, so the charge efficiency is increased and the low-speed torque is raised in return. In the high-speed, the high valve lift and scavenging impulse improve the charge efficiency and engine power.The engine bench test for performance evaluation is used to verify the factors affecting engine power, the results show that import and exhaust system optimization design optimization, rational distribution, can reduce the import and exhaust resistance and improve the engine's charge efficiency, then improve engine power performance. Ethanol gasoline has an small effect on engine power,and make contributions to reduce emissions significantly, engine can be used directly without needing major changes; In addition, the engine test bench is used to verify the factors affecting engine economy,the results show that strict control exhaust temperature, stable fuel supply pressure, is technical support to achieve to control air-fuel ratio precisely, thus improving fuel economy. Through the bench Verifying, measures are proposed to improve the engine power and economy, and prepared for engine bench calibration.The specific requirements and workflow are given for the engine bench calibration optimize the important EMS system parameters such as charge efficiency, air-fuel ratio, ignition timing, EGR rate so that the 4G69 engine calibrated get a large power, low emission, low fuel consumption. Particularly optimization of EGR rate, NOx emissions are controlled effectively. After the data verified by vehicle test meet the requirements, then it can be fixed, the engine calibrated performance test show that the engine's low speed torque and high speed performance is improved clearly, fuel consumption get better and economic region get wider obviously. Finally, BYD company's vehicle fuel consumption test was carried out to verify the design project. The results show that the performance and fuel consumption reach the original development target, the vehicle equipped with the engine calibrated can meet the second-step limit of the standard for automobile fuel consumption.The summary of the research for this thesis is as follows:1)import and exhaust system optimization design, rational distribution, can reduce the import and exhaust resistance and improve the engine's charge efficiency, thus improve the engine's power;2) MIVEC variable valve timing technology can improve the engine power in high speed region, while improving the engine fuel economy in low-medium speed region;3) strict control exhaust temperature, stable fuel supply pressure, is technical support to achieve to control air-fuel ratio precisely, thus improving fuel economy;4) through the EMS engine management system calibration, to meet high demand of the engine power, economy and emission characteristics, compared to 4G64 model, rated power and rated torque increased by 20% and 10% above;5) the reasonable control of the EGR rate reduce NOx emissions by 30% or more in the engine feedback region, while improving fuel economy;6) the engine bench test show that power and fuel consumption reach the original development target, in addition, the vehicle equipped with the engine calibrated can meet the second-step limit of the standard for automobile fuel consumption.