Scaling method is an alternative for thermodynamic design of a new engine. The benefits of this method are the design process can be done quite fast and guarantee that thermodynamic performance of the new engine (derivative engine) will be the same as that of the existing engine (prototype engine). Thermodynamic design by scaling method requires determination of parameters that influence the engine performance; dimensionless groups; and complete specifications of an existing engine. Those requirements are needed as a reference for thermodynamic design of the new engine. This thermodynamic design is a part of research to develop the new engine based on the Sunpower FF300W.