通过理论计算和试验研究，对模件式单排气总管（简称ＭＳＥＭ）系统扩压长支管的非定常流动特性进行了分析，理论计算和实测结果吻合较好．结果表明：ＭＳＥＭ系统采用扩压长支管系统能够明显地降低排气背压和排气总管的压力波动，减少排气系统的能量传递损失，为高增压、超高增压柴油机采用ＭＳＥＭ系统扩压长支管系统提供了理论基础． Through the theoretical calculation and experimental study, the unsteady flow characteristics of the diffuser long branch pipe of modular single exhaust manifold (MSEM) system are analyzed. The theoretical calculation and measured results are in good agreement. The results show that the MSEM system can greatly reduce the pressure fluctuation of the exhaust back pressure and the exhaust manifold and reduce the energy transmission loss of the exhaust system by using the expanded long branch pipe system. The MSEM system is used to expand the high-pressure super-high pressure diesel engine Pressure long branch system provides a theoretical basis.