In this study, the kinematic and dynamic analysis of a modified slider-crank mechanism which has an additional eccentric link between connecting rod and crank pin, as distinct from a conventional mechanism, are presented. This new extra link that may be called the eccentric connector transmits gas forces to the crank, and it also drives a planetary gear mechanism transmitting a great deal of driving forces to the output. In order to drive the planetary gear train, a pinion fixed to the eccentric connector is used. Consequently, the driving force is transmitted to crankshaft by means of two different ways. For the comparison, the dynamic analysis results of developed slider-crank mechanism have been evaluated with respect to that of a conventional slider-crank mechanism. As a result, although both the conventional and the modified slider-crank mechanisms have the same stroke and the same gas pressure in the cylinder, it is observed that the modified mechanism has a bigger output torque than that of the conventional mechanism. (C) 2006 Elsevier Ltd. All rights reserved.