Here is how to add a custom channel (parameter for datalogging) in TunerStudio Ultra (which comes with your ECU). You can follow with the pictures.
Open your project.
1. go to the custom channel editor
2. click on output channel
3. click on the new item icon
4. in the screen that appears, type in a name for your channel
5. then click on the advanced option.
Here is where you enter the formula for the channel, in this case, converter slip.
Enter the info in the red box, press OK at the bottom, then press the save button.
Next will be adding this channel as a datalogging field.