In internal combustion engines, power is taken from a shaft and motor movement is defined by the angular motion of this shaft. This movement refers to the angle of the gear in rhombic drive mechanism engines while taking the name of the crank angle in crankshaft engines. In this study, thermodynamic comparison was performed in a single cylinder, four-stroke spark ignition engine with crank-drive and alternative rhombic drive mechanisms. Maximum cylinder pressure was obtained at 371 degrees for both rhombic drive and crank mechanism. The maximum cylinder pressure of the crank mechanism is 63.1 bar while the maximum cylinder pressure of the rhombic drive mechanism is 64.5 bar. While in the rhombic drive mechanism engine, the amount of heat lost from the cylinder wall is 15.27 J in one cycle, this value is calculated as 13.68 J with a crank mechanism for a cycle.