A converting mechanical system including a dual connecting rod having a top section adapted to be pivotally connected to a piston on a conventional internal combustion engine and a bottom section adapted to be connected to a crankshaft of a conventional internal combustion engine. A support surrounds each dual connecting rod and includes a retractable device. A decoupling device is adapted to be located on the crankshaft a conventional internal combustion engine. The dual connecting rod has a first working position and in which the dual connecting rod is rigid and connected to the crankshaft when the piston moves. In the second working position, the dual connecting rod disconnects the crankshaft from the piston by action of the decoupling device.