In this study, the performance of a turbocharged aerial reciprocating engine under altitude flight conditions was investigated through experimental data and numerical (0D and 1D) approaches in order to develop an unreal-time digital twin engine model in altitude condition for selection and/or identification of the right and/or proper turbocharger. So, the turbocharger selection process algorithm and the digital twin engine model were created based on available experimental data. After that, the data were gone under data cleaning process with regard to four main criteria, which included "boost pressure", "air-box temperature", "engine fuel consumption", and "engine power". Upon the clean data, the engine map and turbocharger map in aspects of engine performance were derived from sea level ambient conditions up to 23000 feet. Keeping following the algorithm, main engine operational points were determined based on "take-off engine performance" and "continuous engine performance" mission modes. The calculations were done on the dimensionless distance between the points and peak efficiency line (PLE), so that the turbochargers major candidate list was extracted. In continuous, the points were extended over different altitude conditions and the most proper turbocharger was determined from the list by "the unreal-time digital twin engine model" and "strategy of maximum matching between the points with a compressor map."