Abstract
This article presents the theoretical basis and original piston conversion result of the IAMZ-236 engine to an oval - drum. Based on the finite element method in software ANSYS 17.2 calculates the interaction of the original piston - cylinder pair and piston - cylinder pair with oval - drum piston to conclude on the effect of the use of the oval - drum piston on a particular engine, for example on the IAMZ-236 engine.