The variable back pressure design adjusts the back pressure according to the rotating speed, and there is no resonance sound at high speed. When the engine is low-speed, the flow speed of gas will slow down, the speed of gas passing through the regulating valve will slow down, the vacuum suction will be small, and the back pressure of waste gas stored per unit time will be large. When the engine is at high speed, the gas flows quickly, passes through the regulating valve quickly, has a large vacuum, has a lot of exhaust gas, and exhausts smoothly at high speed. Achieve the effect of improving torque and horsepower. (Full-speed power) The high speed is about 85 dB, which is an exhaust pipe with obvious display and improved power according to foreign design concepts in China. The sound came out at 2500-3000 rpm, and it quieted down at 4000 rpm.