Throttle Body Sizing Calculator
Pick a throttle body diameter for target HP — balances low-speed drivability against peak flow.
How to Use
- Enter target HP and whether the engine is NA or forced induction.
- Tool gives ideal TB diameter and nearest OEM options.
Target
TB spec
Formula
TB diameter (empirical)
D_mm ≈ √(HP / 0.14) for NA
Forced-induction factor
D_mm · √((14.7 + boost) / 14.7)
Effective area (dual-blade)
A_eff = 2 · π · (D/2)²
Frequently Asked Questions
Bigger is better?
No. Oversize TB = poor part-throttle drivability; the pedal becomes an on/off switch in the first 10° of opening.
Multi-blade DBW?
DBW electronic throttles can compensate for oversize bores with a non-linear pedal map — but the air gap + idle-control response still suffers.
Turbo — does TB need to be as big?
TB is pre-compressor (on most builds). Size for mass flow, not for static CFM at atmospheric.
Common Use Cases
LS swap
Pick between 90mm, 92mm, 102mm based on realistic power target.
Mustang 5.0 upgrade
Decide if twin-bore is justified over single 80-90mm.
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