Problems to be considered in the design of exhaust manifolds:

1. Performance;

2. Cost;

3. The space layout of the whole vehicle and vehicle compatibility;

4 Cold vehicle emission performance

1. For performance, the exhaust back pressure, exhaust uniformity between cylinders, and how to reduce the exhaust interference of each cylinder need to be considered. For turbocharged engines, consider how to balance exhaust back pressure and turbine response. The problem.
1.1 For back pressure and uniformity. One-dimensional thermodynamic calculation will select the appropriate exhaust manifold pipe diameter, the length of each branch pipe, the pipe diameter of the main pipe, and how the manifolds of each cylinder are connected.
1.2 To reduce the exhaust interference of each cylinder, for example, the usual firing order of 4 cylinder engines is 1342, which will be designed such that the 1-4 and 2-3 cylinders will first merge and then merge into the main pipe, which effectively reduces the exhaust interference of the adjacent firing order cylinders. The problem is that such a manifold is more complicated. In addition, theoretically, when each branch of the exhaust manifold is very long, there is basically no problem of mutual influence between each cylinder. At this time, it is also necessary to consider the length of each manifold to ensure that each cylinder row is uniform. The gas uniformity, the very long spatial arrangement of the exhaust manifold, so in all performance models, the exhaust manifold looks very complicated. The stainless steel exhaust pipe has the best performance, the design is more free, the structure looks more complicated, and the cost is higher; the cast iron exhaust pipe is inferior and the cost is lower.