柴油机增压器出口到后处理装置之间的排气管长度影响排气温度，从而影响了SCR后处理装置的工作效率。在发动机台架上进行了排气管长度对排气温度影响的试验研究，结合ETC和WHTC排放循环，对比了排气管是否包裹保温材料对排气温度的影响。试验表明：排气管长度越长，排气温度下降越快，最大温降高达19%，对NO_x排放影响也越大，NO_x排放相对国家标准增加59%；增加保温材料能维持一定的排气温度，但温降最大也达到8%，NO_x排放相对国家标准增加23%。

The effects of exhaust pipe length between the diesel engine turbocharger outlet and SCR device on exhaust temperature affected the efficiency of SCR. Effects of exhaust pipe length on exhaust temperature were conducted on the engine test bench. Based on the emission cycles of ETC and WHTC, the influences of exhaust pipe length and wrapped heat preservation material on exhaust temperature were analyzed. The test results showed that a long length of exhaust pipe would lead to a great drop of exhaust temperature and hence had a great influence on NO_xemission. The maximum drop of exhaust temperature was as high as 19% and the NO_xemission was also 59% higher than the set limit. The heat preservation material could prohibit the heat release. The maximum temperature drop was 8% and the NO_x emission increase by 23% after the insulation work.