How do I calculate what Gear Ratio to enter?
Here is a something that can make life easier when testing on the chassis dynamometer without an engine-RPM pickup. Perhaps you have already been mathematically calculating the overall gear ratio between the engine and the rollers (or absorber shaft). Or maybe you have tried to work this ratio out by trial and error while comparing DYNO-MAX’s Engine RPM with the vehicle’s tachometer.
Smart Ratio – makes it easy to display Engine RPM (by automatically entering the correct “Gear Ratio” for you) when you don’t have a Yellow Tach lead signal. For example: If you’re only capturing the dynamometer’s roller speed via Shaft Magnet RPM-C channel.
To use it:
1) Go into “Tools – Preferences – Console” and activate “Set Smart Ratio (“=”) Key tachometer match point as: 3000 RPM.”
Note: Make sure to set the RPM Source to “#1- RPM-C, RPM-C”, to use this feature.
2) While running a vehicle on the rollers, shift to the fixed transmission gear you want to test in.
3) Accelerate on the rollers until the vehicle’s tachometer indicates a steady 3,000 RPM.
4) Without varying from 3,000 RPM, press your PC’s [ = ] key (equal symbol on main keyboard).
5) You will find that Smart Ratio has updated the Run Information screen’s Gear Ratio – so that DYNO-MAX’s tachometer now matches the vehicle’s (in this gear).
Note: You can modify the default match point (in Tools – Preferences – Console) to any RPM.