Rear Diffuser Angle Calculator

Calculate optimal rear diffuser angle and expansion ratio for maximum underbody downforce generation.

Input Parameters

Results

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Diffuser Angle
°
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Expansion Ratio
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Est. Downforce Contrib
lbs
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Design Assessment
Note: Rear diffusers accelerate airflow under the car, creating low pressure (Bernoulli principle). Single-element diffusers work best at 5-7 degrees. Multi-element (stepped) diffusers can achieve steeper angles without separation.

Reference

Diffuser Angle = arctan((Exit Height − Inlet Height) / Length) Expansion Ratio = Exit Area / Inlet Area Optimal angle: 5°-7° (single element) Max effective: ~12° before flow separation Downforce = ½ × ρ × V² × Cp × Inlet Area