Abstract This work presents the development of a virtual instrument for the acquisition of temperature data of a 3500 cc diesel engine and the calculation of its thermal efficiency at three different speeds, the analysis was made according to the standard cold air parameters for a diesel engine. To measure the temperature, type K thermocouples distributed around the combustion chamber and the engine exhaust was used; the data acquisition was carried out through a cDAQ-9178 and a NI-9213 thermocouple module from National Instruments.