Mechanical load of piston applied in downsized engine

• The piston of real engine BMW 530i was the object of project.
• The downsizing ratio by 0.25 was applied, giving changing from 2979 ccm to 2250 ccm.
• Downsizing piston gave increasing translation displacement vector by 41.7%.
• Downsizing piston gave increasing Huber–Mises stress by 35.9%.
• Reduction of specific fuel consumption by 6.8% in downsized engine gave lower CO2.

Carbon dioxides, which take part in greenhouse effect and rapid increase of the prices of fuels, are the major reason why it is necessary to design low fuel consumption engines. Automotive sector is one of the few sectors where CO2 emissions are still increasing very fast, reaching a level by 26% in total only from road transport. So, the European Union acts program in cutting overall emission of greenhouse gases and engineers have to care about environment.One of the methods that affect lower fuel consumption is engine downsizing. Downsizing is a method to reduce fuel consumption by decreasing engine swept volume. To achieve the same level of performance it is necessary to apply many techniques, with charging being the first of all. Other suitable techniques e.g. variable valve timing or variable compression ratio are used with various combinations.The subject of this paper was chosen because downsizing is a very interesting trend in automotive engineering. Lots of engines’ manufacturers develop and introduce this method. Moreover ecology and economy are also relevant. The paper considers the downsizing method in case of piston. Analysed parameters e.g. Huber–Mises stress and transitional vector displacement in piston before and after downsizing were studied with Finite Element Method approach.