Why engine need the back pressure?

Back pressure in an engine is essential for maintaining optimal performance and efficiency. It helps in the proper scavenging of exhaust gases, ensuring that fresh air-fuel mixture is effectively drawn into the combustion chamber. Additionally, a certain level of back pressure aids in improving torque and power output, particularly at lower RPMs, by enhancing the overall tuning of the exhaust system. Without adequate back pressure, engines may experience a loss of efficiency and power, leading to poor performance.