Adjusting Speedometer Calculation on Powervision

Looking to change your speedometer reading? Here we will show you the steps to adjust your speed output for larger tires, tracks… ect. This is not terribly hard, but certainly not worth it for small tire size changes. For extremely large tire sizes, tracks, gearing changes.. ect this would be the reason to change the speedometer reading. You will need a windows computer and basic computer knowledge to get this done.

Step 1: You must have the speedo calibration portion of your tunes unlocked from us! We leave this portion of the tune non password protected so you can edit. We don’t normally do this unless it’s requested. If you need this done, contact us. A $50 fee may apply.

Step 2: Download and install the Dynojet Powercore Software here: https://www.dynojet.com/downloads/power-vision-3/

Step 3: Open the powercore software menu, then open the C3 tuning software. See image below. **Note: DynoJet now requires creating a DynoJet account to use the Power Core software.

Step 4: Plug your Powervision into the computer with the supplied USB cable, then open the POWERVISION drive folder. Now double click the tune file you wish to edit the speedo calibration. This will open the file in the C3 software. See image below.

Step 5: Hit CANCEL when asked for the password, which will display only the unlocked parameters. If nothing shows, nothing is left unlocked in your tune. See image below.

Step 8: Click on Speedo Calibration and it will display a number. THIS NUMBER IS NOT CORRECT! The downfall of this process is as soon as we enable the speedo switch, the speedometer calibration number is off from the start. See image Below.

Step 9: Normally the value 26.2 is closer to the stock size. Punch that in, then hit “Save As” in the top corner. We’d suggest saving the file as the same name, just with the number you type into the box. This is easy to keep track when making changes. Make sure you save the file to the POWERVISION drive. You may also want to make a copy to your computer hard drive as a backup. See image below.

Now go upload that tune to your ECU and run the vehicle around 50mph. Record your speed with your phone or GPS. If the calculation is off, figure out the % it’s off (Google percent difference calculator). Now you can change the value in C3 according to that % by using the simply % change at the bottom of the screen and hit the plus or minus button. See image below.

Double check the reading is accurate, some fine adjustments may be needed.