Although we can only see one pipe head sticking out from the outside, we can always find that the exhaust system of each car is different from each other through careful observation, especially the design of the exhaust manifold is always strange. The designer's design of the pipeline as a twisted and deformed shape is not a fad, but a modeling design scheme based on comprehensive consideration of many factors.

Exhaust is the main factor to be considered in the design of manifold shape. As everyone knows, emission regulations are becoming more and more strict. In order to comply with exhaust emissions, fuel should be fully burned as much as possible. The optimization of traditional engine exhaust system is also a key point. Combustion requires full oxygen, so the requirement for the emission system is to allow the exhaust gas in the cylinder to be discharged normally and fresh air to come in, Don't let the excess exhaust gas stay in the cylinder to take up space.

At present, engineers deal with the exhaust problem. The general design idea is to extend the pipeline as far as possible, so that each air passage is independent of each other, and reduce the pressure wave interference of exhaust gas from each cylinder. Therefore, the strange and twisted exhaust manifold we see is basically a plan to make the pipeline as long as possible in a limited space. It is also not allowed to twist at will. To make the gas pass as smoothly as possible, there should be no sharp turns. In addition, it is necessary to consider the uniformity of the exhaust gas in the section, that is, to make the exhaust gas in each cylinder pass through a basically similar path, so that the three-way catalyst can contact the exhaust gas as evenly as possible, so as to maintain a state of efficient conversion of exhaust gas.

In order to ensure the reliable operation of the manifold, mechanical strength, thermal stress and vibration should also be considered in the design. Everyone knows the power of resonance. In order to prevent our exhaust manifold from being subject to engine vibration, computer simulation should be used to calculate the natural frequency during the design.