What it does
In any given gear, engine RPM and vehicle speed move together at a fixed ratio. The Gear Ratios page stores that relationship for each gear, and the ECU uses it to work out the current gear on the fly. That gear channel then feeds functions like gear-based boost and timing corrections, flat shift and torque converter lockup.
Before you start
You need a vehicle speed sensor wired in and calibrated first. If the speed reading is wrong, every ratio learned from it will be wrong too. See Vehicle Speed Sensors.
Two ways to fill it in
- Calibrate on the road: drive with NSP connected and press Calibrate while holding each gear. Hold a steady speed with the clutch fully engaged (or the converter not slipping badly) for the cleanest result, and have a passenger work the laptop.
- Enter known values: if you already know each ratio, type them in directly.
Check it
Afterward, log gear alongside RPM and speed. The gear channel should change cleanly on every shift and never hunt between gears while cruising.
Related: Gear Detection and Transmission Control.
