Introduction to exhaust manifold
The exhaust manifold is connected to the engine block, and the exhaust of each cylinder is collected and introduced into the exhaust manifold with divergent pipes. The main requirement for it is to minimize the exhaust resistance and avoid mutual interference between the cylinders. When the exhaust gas is excessively concentrated, mutual interference occurs between the cylinders, that is, when a certain cylinder is exhausted, it is just the exhaust gas that is not discharged from other cylinders. In this way, the resistance of the exhaust gas is increased, thereby reducing the output of the engine. The solution is to separate the exhaust of each cylinder as much as possible, one branch per cylinder, or one branch of two cylinders, and make each branch as long as possible and shape - to reduce the gas interaction between different tubes. In order to reduce the exhaust resistance, some cars use stainless steel tubes to make exhaust manifolds.
The exhaust manifold should take into account engine power performance, engine fuel economy performance, emission standards, engine cost, matching vehicle front cabin layout and temperature field.
The exhaust manifolds currently in common use are classified into two types, cast iron manifolds and stainless steel manifolds, in materials and processing techniques.