How to be setting Tach RPM Ratio?1. Turn on the power supply first.2. Press and hold the mode button for 3 seconds to enter the setting speed ratio mode. then adjust speed ratio from 1-300 according to your request.3. After setting, Data is automatically saved.4. Please note: If your sensor is installed on the flying wheel panel, the RPM ratio is equal to the number of gears of the engine; If the speed signal takes from W-Terminal, the RPM ratio is equal to the half of the number of poles.5. Normally, When the engine at idle state, tachometer shows 600-800rpm that means speed ratio is correct. If not, you can turn down or turn up speed ratio to check RPM difference.