the exhaust manifold is connected to the cylinder block of the engine, and the exhaust of each cylinder is concentrated into the exhaust manifold, with divergent pipes. The main requirement is to minimize the exhaust resistance and to avoid interference between cylinders. When the exhaust is too concentrated, there will be mutual interference between the cylinders, that is, when a cylinder is out of the air, it just happens to run into other cylinders without exhaust. In this way, the exhaust resistance will be increased and the engine output power will be reduced. The solution is to make the cylinders as separate as possible exhaust, one branch per cylinder, or two cylinders, one branch, and each branch as long as possible and forming - to reduce the influence of gases in different pipes. To reduce exhaust resistance, some racing cars use stainless steel tubes to create exhaust manifolds.         ;       the currently used exhaust manifold is divided into two types from material and processing processes: cast iron manifold and stainless steel manifold.                the exhaust manifold should take into account the engine power performance, economic performance, fuel cost, emission standards, engine, vehicle cabin layout and temperature field etc..