Tuning can be performed in various ways:
- Directly within the engine or vehicle ECU.
- Indirectly, using a "piggyback" module that takes over control from the standard ECU. This is often due to the impossibility of accessing or opening the ECU.
The module inputs the airflow signal and ignition signal, processing them through its internal mapping before returning them to the ECU. This method allows virtually all ECUs to be reprogrammed via various signals.