Exhaust Backpressure Calculator

Calculate exhaust system backpressure from pipe diameter, length, and flow rate using Darcy-Weisbach equation.

Input Parameters

Results

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Total Backpressure
psi
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Backpressure
in Hg
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Est. HP Loss
hp
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Exhaust Velocity
ft/s
Note: Exhaust backpressure above 3 psi typically causes noticeable power loss. Each 1 psi costs roughly 1-2% power. Larger diameter pipes reduce velocity and pressure drop. SAE J1723 exhaust testing.

Reference

Velocity = Flow / (Pipe_area × 60) f = Darcy friction factor (Swamee-Jain approx) Pipe Loss = f × (L/D) × 0.5 × rho × V² / 144 Bend Loss = N × K_bend × 0.5 × rho × V² / 144 Cat Loss: Standard ~1.5 psi, Hi-Flow ~0.7 psi Total = Pipe + Bends + Catalyst