The exhaust manifold is connected with the engine cylinder block, which gathers the exhaust of each cylinder and leads it to the exhaust manifold, with divergent pipes. The main requirements for exhaust manifold are to minimize exhaust resistance and avoid mutual interference between cylinders. In order to reduce exhaust resistance, some racing cars use stainless steel pipes to make exhaust manifolds. When the exhaust gas is too concentrated, the cylinders will interfere with each other. That is, when a cylinder exhausts, it just encounters the exhaust gas that is not completely discharged from other cylinders. This will increase the resistance of exhaust gas and thus reduce the output power of the engine. The solution is to separate the exhaust of each cylinder as far as possible, one branch for each cylinder or one branch for two cylinders.