In order to conveniently study and accurately evaluate engine performance under transient operation con-ditions, the European Transient Cycle (ETC)was analyzed and it was determined that operational conditions of con-stant rotation speed and increasing torque might be taken as the typical transient operation conditions of an engine. Simultaneously, a test analysis was carried out for the conditions of constant rotation speed and the loading process at different transient times, and the following parameters were proposed:the"lag coefficient", which is an evalua-tion index for the degree of delay of the performance parameters of an engine in the transient process;the"deterio-ration coefficient" ,which is an evaluation index for the worsening degrees of the transient performance of an en-gine;the"transient total" and"transient average", which are the indices for evaluating the comprehensive transi-ent performances of an engine. The experimental results show that the above-mentioned evaluation methods may e-valuate the performances of an engine clearly and comprehensively throughout the entire transient process. As far as the entire loading process is concerned, the loading speed, gross fuel consumption and NOx emissions have an ap-parent compromised relation with the gross emissions of soot and CO.%为了使车用柴油机瞬态性能研究更简便准确地评价瞬变过程中发动机性能参数的变化，分析了ETC瞬态测试循环，得出了恒转速增扭矩工况可以作为发动机典型的瞬态研究工况的结论。同时，对柴油机开展了恒转速、不同加载时间加载过程的试验分析，提出了表征瞬变过程中发动机性能参数延迟程度的评价指标---“滞后系数”和表征发动机瞬变性能恶化程度的评价指标---“劣变系数”以及评判发动机综合瞬变性能的评价指标---“瞬变总量”和“瞬变平均值”。试验结果表明，上述评价方法能较全面、清晰的评判发动机在整个瞬变过程的性能情况。对于整个加载过程而言，加载速率、总燃油消耗量和NOx排放量与碳烟和CO总排放存在明显的折衷关系。
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