Estimate the optimal exhaust pipe diameter based on engine horsepower levels.
Performance Specs
Diameter Results
Enter engine horsepower
About this calculator
Quick Reference
CFMCubic Feet per Minute
VelocityExhaust gas speed (ft/s)
SingleOne main exhaust pipe
DualTwo parallel exhaust pipes
Overview
Selecting the correct exhaust pipe diameter is a balance between flow capacity (minimizing backpressure) and maintaining exhaust gas velocity (improving scavenging).
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Pro Tips
Rule of thumb: 2.2 CFM of exhaust flow is required per horsepower.
Optimal velocity is approximately 200 to 300 feet per second.
A pipe that is too large can actually reduce performance by slowing down the gas velocity too much.
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Fun Facts
"Smaller diameters increase gas velocity, which help 'scavenge' the cylinders at lower RPMs."
"Large diameters are necessary for high-RPM power where total flow volume is the limiting factor."
"Turbocharged engines generally benefit from larger exhaust pipes as the turbo relies on pressure differential."
