We get questions all week long from our customers on how to calculate what header size they need, what length of primary tubes, collector sizing, and even turbo selection.
Although this is by no means an exhaustive list (header pun), it's certainly a great starting point to begin your custom header design.
Use these equations and general rules of thumb as a starting point, but know that all definitive tuning and sizing is best done as a blend on a dynamometer, and the drag strip.
Tubing ID Cross-Sectional Area (CSA):
Turbocharger Minimum CFM Output:
General Header Sizing
Rules of Thumb
Quality Tubing flows ~115-120 CFM per sq. inch of cross-sectional area (CSA)
Exhaust tubing requires about 2.2 CFM per horsepower.