India is considered to have one of the maximum two wheeler density in the world. Hence, all the scooter and motorcycle manufacturers are striving to keep their market share by quickly bringing quality products with high mileage at a cheap price tag. As emission norms are becoming stringent day by day, these OEMs have to take care of every detail in the engine that is driving their vehicles. So today's engineers are obliged to refine and improve the technologies they use, faster and with greater accuracy than ever before. This paper focuses on reducing Cylinder Bore deformation for a two wheeler engine through CAE simulation. In standard testing conditions this deformation was observed to cause engine seizure. Bore deformation is of great significance to the overall performance of an engine. It can increase oil consumption, blowby and emissions and may influence piston dynamics to a great extent. These deformations are however, difficult to measure and being in micron level, are often prone to misinterpretation. Moreover, making physical prototypes with frequent design changes for reducing bore deformation is a highly time consuming and costly exercise since it involves most critical engine parts. These parts are often long lead time items in engine development cycle. This, with the added constraints on packaging and styling in two wheelers, leaves very little variations to be done on the design. Therefore, to cut down the design cycle time, virtual simulation methods are preferred. A high cubic capacity two wheeler gasoline engine is studied to evaluate and reduce deformation of cylinder liner. The cylinder head assembly comprising of major components like head, block, liner, etc. was meshed with second order elements and the analysis model was set up in a commercially available numerical code. The base design was then subjected to bolt pretension loads for simulating liner deformation. Based on this finite element analysis, the scope of reducing deformation was observed. Subsequently, a number of design modifications on liner, block and crankcases were made and thoroughly simulated under same loading conditions. This way a final proposal giving acceptable deformation was reached. The results of the final proposal, when compared to base design, indicated a useful reduction in deformation in the localized liner area without affecting stress and stiffness in other areas. The effect of modifying the cylinder head design on liner deformation was also studied. This paper may serve as a good reference for engineers who are targeting to reduce liner deformation in two wheeler engines.
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