Assuming that the definition of the control system and its functionality has been performed already in the previous development phases (e.g. by HIL controller assessment), a comprehensive pre-calibration of the ECU needs to be performed in a special test phase following combustion development.
The pre-calibration of the ECU is performed when the engine specifications including the fuel injection equipment and other components affecting engine efficiency are finalised and all components have at least "production intent" level.
Engine combustion development and ECU pre-calibration are best performed in one sequence by the same development team. Modern testing procedures and application tools are used intensively to quickly produce reliable data sets.
A high quality engine pre-calibration will reduce the time needed for vehicle testing, which is then only performed for validation.