The role of real power output from farm tractor engines in determining their environmental performance in actual operating conditions

[Display omitted] •In actual operating, the internal losses of the engine must be taken into account.•The internal losses of engine are determined using the Willans method or the CAN data.•The internal losses of engine can be described with a polynomial for a given engine.•Bypassing the internal losses of engine improves its environmental performance.•Emissions in approval tests and in real using conditions cannot be directly compared. The paper discusses the determination of engine torque to be used to calculate work performed by a non-road vehicle when determining specific exhaust emissions. During investigations related to the environmental indexes under actual operating conditions, the value of torque is pulled from the vehicle OBD system. It is estimated based on the pressure and duration of the fuel injection. The work of an engine calculated in this way is overrated. It allows for the engine internal losses such as aerodynamic resistance and internal friction losses. The paper presents tests on a farm tractor, in which a portable chassis dynamometer and a portable exhaust emissions measurement and data recording systems were applied. In the performed tests, the engine operated at steady work points: defined engine speeds and loads. Based on the Willans method, the data from the vehicle on-board diagnostic system and the calculated values of the fuel consumption a correction curve was determined. It should be used when correcting the engine torque during measurements under actual operating conditions. Based on the recorded concentrations of the emission components, specific emission was calculated allowing for the corrective calculation. This was used to perform a comparative analysis with the emission limits specified by the Stage IIIB standard that the test object was compliant with. The presented research methodology may be successfully applied in testing other non-road machinery whose environmental indexes are defined based on specific emissions. In research of machines in actual condition, necessary is to determine the engine internal resistance and take it into account when determining the engine torque in the field tests. This will allow a determination of the real environmental indexes.