What is the diameter of the exhaust pipe?
3 Answers
For ordinary household cars, the diameter of the exhaust pipe is related to the engine displacement. For example, a 1.0L engine like the QQ typically has a 38mm (circumference) exhaust pipe, a 1.4L engine has a 45mm exhaust pipe, and a 1.6L engine has a 51mm exhaust pipe. Additional information: The exhaust pipe is part of the engine's exhaust system, which mainly includes the exhaust manifold, exhaust pipe, and muffler. The three-way catalytic converter, which controls engine pollutant emissions, is also usually installed in the exhaust system. The exhaust pipe generally consists of a front pipe and a rear pipe. Car owners should pay attention to maintaining the exhaust pipe, with three key tips: waterproofing, rust prevention, and cleaning.
Last time I modified my exhaust, I specifically measured it, and the differences between cars are quite significant. For small cars like the Fit with a 1.5L engine, the stock exhaust is about 5cm in diameter, but enthusiasts often upgrade to 7cm for that satisfying sound. However, increasing the diameter must match the engine. My 2.0T hot hatch originally had a 7.6cm exhaust, but after upgrading to 9cm, it lost low-end torque. Eventually, I settled on 8.5cm to balance sound and performance. High-displacement naturally aspirated cars are even more extreme—I’ve seen a C63 owner running dual 12cm pipes, thicker than my arm. A word of advice: don’t just focus on diameter; backpressure design is crucial. Otherwise, like my neighbor’s Civic with a straight-through pipe, the whole neighborhood knows when he leaves for work at midnight.
With twenty years of experience in car repairs, I've handled more exhaust pipes than you can imagine. For economy cars like the Corolla, the stock tailpipe diameter is usually around 5-6 cm, which is both sufficient and cost-effective. German luxury brands like BMW, Mercedes, and Audi typically use dual 7.5-8.5 cm exhaust pipes for their 2.0T models, while quad-exit setups reduce each side to 6 cm. American muscle cars take it to the extreme—the Mustang GT's 5.0L V8 comes stock with massive 10 cm chrome pipes. When modifying, note that every 1 cm increase in diameter lowers the exhaust note frequency by about 100 Hz. Last week, I worked on a customer's car with a 15 cm straight pipe paired with a 1.6L engine—it completely killed low-end torque and increased fuel consumption by 2 liters. Don't blindly chase bigger pipes; OEM engineers know what they're doing.
