The function of the exhaust system is to exhaust the exhaust gas from the cylinder to the atmosphere with as little exhaust resistance and noise as possible. The exhaust manifold mainly includes the exhaust manifold, the exhaust pipe and the muffler. The exhaust gas is connected to the exhaust port of the combustion chamber through exhaust manifold, the middle part of the exhaust pipe (including the three way catalytic converter) and the exhaust pipe tail (commonly called tail row), and finally discharged to the outside air.
In the above intake system modification has been mentioned, reduce air resistance and exhaust resistance, improve the cylinder pressure, reduce the intake temperature, reduce exhaust pipe residual gas pressure, increase the intake area can improve the volumetric efficiency of the engine, the engine power and torque increase, improve power performance. So in the modification of the exhaust system, should as far as possible to expand the pressure tube free exhaust truncated cylinder and exhaust, make full use of exhaust inertia, reduce the exhaust resistance, reduce exhaust residual gas pressure, reduce the content of residual gas, eventually making smooth exhaust, fast, improve volumetric efficiency, better power performance the. To make the exhaust system get higher exhaust efficiency, we should make full use of the back pressure (back pressure) and "sipping" effect of the exhaust system during operation. When the engine is working, the exhaust gas transported by the exhaust system is not continuous, but a wave. The more the number of cylinders or the higher the speed of the automobile engine, the more dense the waste gas wave is. The low pressure produced by high pressure exhaust wave is back pressure when the cylinder is discharged at high speed. Proper backpressure can make the exhaust system have a good sipping effect. The principle is: if the exhaust pipe diameter is moderate, the exhaust gas discharged from the first cylinder will be pushed down quickly after the expansion of the exhaust cylinder, and at the same time, a low pressure area will be generated in the upstream part, which will exhaust the second exhaust gas from the engine. Low voltage second wave gas in the inner wall of an exhaust pipe is discharged when the pressure in the rear of the third wave in the sucking exhaust gas, and so on, so that the engine can easily complete the exhaust operation than the exhaust efficiency than no exhaust system is higher, less residual waste gas in the cylinder, and the cylinder can be hold the fresh air for combustion is more. Therefore, only the full use of back pressure and sipping effect, the exhaust system can reach higher performance.