Will Only Modifying the Rear Section Result in Loss of Low-Speed Torque?
1 Answers
Modifying only the rear section of a car's exhaust system can lead to a loss of low-speed torque. The lower the torque at low RPMs, the more noticeable the effect, especially with a smaller power-to-weight ratio. Reasons for low-end torque loss when modifying the rear section: Any alteration to the exhaust velocity will result in varying degrees of low-speed torque loss, which becomes more pronounced with a smaller power-to-weight ratio. Whether modifying the rear section or the mid-to-rear section, these changes directly affect exhaust pipe compression, which in turn impacts exhaust velocity. At low speeds, the engine operates under higher load with lower combustion efficiency. If the modified exhaust velocity increases, incompletely burned air-fuel mixture may escape through the exhaust valve, reducing combustion efficiency and causing torque loss at low speeds. The faster the exhaust velocity, the more noticeable the low-end torque loss—this explains why straight-through exhaust systems exhibit greater low-end torque loss compared to systems with internal backpressure. For economy-displacement vehicles where sound enhancement is the primary goal, simply replacing the rear section or opting for an exhaust system with a variable exhaust valve may suffice. Exhaust system design considerations: Designs prioritizing reduced engine noise may compromise exhaust velocity, thereby lowering engine efficiency. While improving intake and combustion, exhaust efficiency must also be enhanced. Many modern systems adopt straight-through designs, modifying the mid and front sections of the exhaust system by removing purification devices like mufflers. This shortens the entire exhaust process, allowing exhaust gases to exit after minimal treatment. Such modifications result in quicker vehicle acceleration.
