In any given gear, engine speed and vehicle speed move in a fixed ratio to each other. Divide one by the other and you get a number that's different for each gear. The Gear Ratios function in ESP stores that number for every gear, so the Elite can compare what it sees live against the list and decide which gear you're in. That gear value can then feed other functions, such as boost or torque management corrections by gear.
Before you start
The ECU needs an accurate road speed signal for this to work. Wire in a vehicle speed sensor and calibrate it first. If speed is wrong, every ratio you record will be wrong too.
Two ways to enter the ratios
On the Gear Ratio tab you can either:
- Calibrate on the road. With the laptop connected and ESP online, drive the car in each gear and press the Calibrate button for that gear. Have a passenger work the laptop.
- Type them in. If you already know the values for your combination, enter each one by hand.
For road calibration, hold a steady speed with the clutch fully engaged (or the converter locked on an automatic, where possible) when you press the button. Slip at the moment you calibrate gives a ratio that doesn't match normal driving. After you're done, drive through the gears and watch the gear channel to confirm it tracks every shift. If you change tire size or diff gearing, redo it.
Related: gear position and torque management.
