Abstract:In this paper, BOOST and FIRE software were respectively used to establish thermodynamic model of an engine’s intake, an exhaust system and internal CFD steadystate model of the exhaust manifold. Then initial calibration and boundary condition fusion were conducted through experimental data. The pressure loss and transient flow field distribution of the exhaust manifold in low and highspeed conditions were analyzed by one-dimensional(1D) and three-dimensional(3D) coupling methods. According to the evaluation test results, the optimized structure has significantly improved internal flow field fluency and the exhaust uniformity of each manifold, reduced back pressure, shortened ignition time, and improved the maximum torque of the engine to a certain extent.