Real Time Tuning (RTT™)

RTT™ is an operating system modification available for certain vehicles with LS1 engines. This mod allows users to change the values of certain parameters in real time while connected to the vehicle in VCM Scanner.

NOTE: To do this, the customized operating system copies parameters that are normally stored on the controller's internal flash drive into the controllers RAM memory. The parameters in RAM can then be modified in real time, without flashing the vehicle.

After tuning is complete, the final parameters can be written to the PCM and stored permanently using VCM Editor.


Software only, no special hardware required
Enough functionality to tune the car. (Not every parameter requires real time support.
Easy to use
Low cost

CAUTION: Do NOT attempt changing real time tune values while driving the vehicle. Doing so may cause driver distraction and possible vehicle crash. Real time tuning is designed for quick tuning under controlled conditions like an engine or chassis dynamometer.

CAUTION: Use caution when entering values into the real time tuning tables. Improper use may cause vehicle damage and or unsafe driving conditions. The user assumes all safety responsibility for use of and values entered into real time tuning mode.


1. In VCM Editor, open a calibration file read from a vehicle that supports the RTT operating system modifications. See Operating System Enhancements with RTT for a list of these mods and the vehicles they can be applied to.
2. Apply an HP Tuners OS modification that includes RTT capabilities. See Applying a Custom OS with RTT for instructions.
3. Select the RTT Mode and write the new calibration to the vehicle. See Selecting the RTT™ Mode.
4. Open VCM Scanner.
5. Click to establish a data connection. The RTT icon will appear in the toolbar.

6. Click the RTT icon to open the Real Time Tuning window. See The Real Time Tuning Window for more information on using this window.

NOTE: This icon will not be displayed unless you have flashed a tune to the vehicle with RTT Mode set to anything other than Disabled.

7. For each table you wish to modify:
a. Use the number buttons at the top of the window to select the table you want to modify. Intially, the table will appear blank because its data has not yet been copied from the flash drive.
b. Click to copy the selected table to the controller's RAM memory and tell the controller to use the copy in memory rather than the original on its internal flash drive.
c. Edit the table as desired. Your changes will take effect in real time.
d. When you have built a table that you feel is worthy of applying to the vehicle permanently, right click on the table and select Copy.
e. In VCM Scanner's toolbar, click to disconnect.
f. Open VCM Editor and navigate to the tab containing the table that you are finalizing.
g. Right-click on the colored background of the table's name and select Paste.
8. When you are ready to write a batch of changes to the vehicle's flash drive, perform a calibration only write to the vehicle.

NOTE: You do not have to disable the RTT™ mode in VCM Editor to write changes. You can leave the mode set to a desired RTT mode and continue real time tuning your vehicle as needed.