cylinder assembly collapsing said vapor is attained via injection of a minute amount of relatively cold fluid 1 through valve 18 a or 18 b as shown in fig5 a and 5 b vapor collapsing can be seen as a sudden condensation which generates a vacuum in the bottom ventricles when this phenomena occurs it causes the piston 8 a or 8 b to return to its bottom dead center thereby provoking another power stroke while moving downward in essence when one piston is executing a traditional power stroke due to vapor expansion the other piston is also executing a power stroke in the opposite direction utilizing the vapor contraction instead of its expansion thereby forming a tandem thermodynamic cycle unlike traditional vapor cycles when the piston 8 a or 8 b returns to its bottom dead center position it provokes a suction effects on the respective top ventricle 7 a or 7 b on the blood side for example the action of suction executed by piston 8 a on the blood side is synchronized with the action of compression executed by piston 8 b also on the blood side the synchronization is achieved through the connecting rods 14 a and 14 b to the common crankshaft 13 once most of the vapor.