The function of the exhaust system is making the exhaust resistance and noise as small as possible, and to drive the exhaust gas within the cylinder out of the atmosphere. Exhaust system includes an exhaust manifold, exhaust pipes and mufflers.The exhaust gas discharged from the exhaust port which is connected to the combustion chamber, via the exhaust manifold, the front exhaust pipe and exhaust pipe tail section, then finally to the outside air.

For the exhaust system modification, It should expand the exhaust gas freely as much as possible, to cut the pressure difference between exhaust pipe and inside cylinder, and making full use of the exhaust inertia, to reduce the exhaust resistance and exhaust pipe residual exhaust gas pressure, then reduce the residual gas content of the exhaust gas, so that finally making the exhaust flow and fast, improving the efficiency of volume and geting a better dynamic performance. To make the exhaust system for higher exhaust efficiency, we should make full use of the exhaust system back pressure generated during operation. When the engine works, the exhaust system conveying the gas is not continuous; The more of cylinder engine amounts or the higher rotational speeding, the denser of exhaust pulse. The high pressure exhaust wave is discharged out of exhaust cylinder in high-speeding then produces the depression, which is called back pressure. The principle is: if the diameter of the exhaust pipe is moderate, the first wave of exhaust gas discharged out of the cylinder to press the exhaust pipe wall and discharged downstream quickly after expansion, while generating a low pressure area in the upstream part to absorb the engine exhausting the second wave gas, and so on, it is not difficulty to make the engine complete the exhaust. Therefore, only making full use of the effect of back pressure and absorbing to achieve the higher performance.