'Advanced Tuning' let's you access the data files, any edits to these will auto save. When using 'Basic Tuning' remember to click 'Apply'.
You can now modify the car using either 'Basic Tuning' or 'Advanced Tuning'.The program will automatically select the tune you just made. Type a name for your tune in the textbox under 'New Tune Name:' and click 'Create New Tune'.Click 'Select Assetto Corsa Folder' and a dialog window will pop up, select your Assetto Corsa install folder, it's usually under Steam/steamapps/common/.Open program by clicking the 'Assetto Corsa Car Tuner.exe'.The program saves tunes as a seperate car that is selectable as an upgrade in-game, the original car is therefore not changed! Once you have made your changes, click save tune (If you used Basic Tuning click 'Apply' first), then install tune to have it available in-game. Basic Tuning let's you modify preselected data like torque, turbo's, wheel drive and more! Advanced Tuning is for the more experienced tuner, and let's you mess around with the data files. You can do so with either 'Basic Tuning' or 'Advanced Tuning'. This program allows you to tune any car in the game.
If you make a cool video using a tune made with this tool, send it to me and I'll put it up here.