Exhaust pipes are a system of tubing which leads exhaust gasses away from the engine bay and out the back or sides of the vehicle.
Exhaust pipes come in various diameters, usually somewhere between 2.0 to 3.5 inches. They usually have components along their length, instead of being one long solid pipe. However, some performance vehicles do have just a solid pipe on them, which is the most free-flowing design, but is also usually the loudest as well.
Pipe Diameter & Exhaust Flow
The diameter of the pipe has performance trade-offs between flow rate and resistance/pressure. The optimal diameter will be based on where the builder wants the peak torque to occur on the RPM range. For example, the optimal diameter of a pipe for a 400 cubic inch motor at 4000 RPM is about 1.8 inches, while at 5000 RPM it is 2.0 inches. The formula for building the ideal exhaust system is shown below:
- Area of Primary Pipe = RPM × Motor Size ÷ 705,600
- Pipe ID2 = RPM × Motor Size ÷ 705,600 ÷ .7854
- Pipe ID2 = RPM × Motor Size ÷ 554,177
- ID = (RPM × Motor Size ÷ 554,177).5
- OD = (RPM × Motor Size ÷ 554,177).5 + .098”