SETTING ratings for diesel engines takes laboratory testing and field experience for critical parameters such as smoke, piston temperature, and exhaust temperature.
Rating is based upon theoretical considerations, plus the approval of the engine itself. Factors in rating considerations include a knowledge of the application of the engine, and whether its use is to be intermittent or continuous.
Ratings by the manufacturer are not always accepted by the engine user, however. The user will run the engine at the load most profitable for him, which may be above or below that recommended by the manufacturer.