Weve all heard rumors of people who swap on a bigger exhaust system and actually lose power. How can this be?
“An engine needs a certain amount of backpressure , or resistance to flow, below the torque peak of the engine,” says Muffler Guru. When you take away that restriction, … the engine loses quite a bit of performance below torque peak, which is right where you drive for gas mileage and towing, when you’re just driving around stoplight to stoplight, accelerating away from a stop. “An oversize exhaust will not hinder performance at high rpm. An oversize exhaust system would do about the same at high rpm, but you would lose power at low rpm. So the bigger is better theory doesn’t work on exhaust systems.” And we aren’t just talking about 1 or 2 lb-ft of torque, either. “If your engines torque peak is 4500 rpm,” says Guru, “you spend a lot of time below that peak, which is where you lose your performance. And it can be significant. We’ve seen losses of 20 or 30 lb-ft of torque, and if your engine only makes 150 lb-ft to begin with, you’re losing 20 percent.” The key, once again, is to get
