MAF Sensor Sizing Calculator
Size a MAF (mass airflow sensor) housing for correct velocity at peak flow — avoids pegged voltage and poor low-load resolution.
How to Use
- Enter peak mass flow (lb/min) — use the Intake CFM tool or dyno data.
- Enter idle CFM for the low end (typical 10-15% of peak).
- Pick a candidate MAF diameter and see velocity at idle and peak.
Flow
Velocity through MAF
Formula
Density at IAT
ρ = 0.0765 · (530 / (T_°F + 460)) lb/ft³
Volume flow
Q_cfm = ṁ / ρ
MAF velocity
v = Q / A, A = π · (ID/2)²
Good range
10 m/s (idle) → 80 m/s (peak)
Frequently Asked Questions
What velocity range is good?
Most automotive hot-wire MAFs resolve best 10-80 m/s. Below 5 m/s: noisy idle. Above 120 m/s: pegged 5V, transfer function saturates.
OEM MAF sizes?
GM 3" LS1, 3.5" LS2, 4" LS3/LS7, 4.5" LS9. Ford 80mm SN95, 90mm Cobra, Lightning HPX.
Can I use a larger MAF for big HP?
Yes, but retune the MAF transfer function to match the new housing cross-section (or the ECU will over-fuel at low load).
Common Use Cases
Turbo upgrade
Swap to a larger-diameter MAF before pegging the sensor.
Supporting mod
Prevent part-throttle drivability issues after big cam + heads.
Last updated: