A new engine design concept, characterized by a single cylinder-double piston and a cycloid crank rotor instead of the conventional crankshaft has been developed recently by Gul & Co Development AB, Sweden. The rotor (crank disc) is equipped with an oval groove in the shape of a sinusoidal cycloid according to the expression varies from 0 to 1. Inside the oval groove a ball rolls/slides in order to transfer force from the piston to the rotor. Such a rotor contains groove surfaces for the valve movement control as well. Each turn of the rotor corresponds to four strokes for both the pistons. Thus, a full 4-stroke engine cycle is developed for a single non-conventional crankshaft revolution.Having the extra freedom to select an optimal piston movement, the new design is believed to have the potential to provide low emissions, low noise levels and lower fuel consumption. Therefore, it has been subjected to an engine thermodynamics simulation, to provide an insight to engine performance.Simulation results and preliminary laboratory tests have shown that the optimized cycloid crank rotor, which further intensifies the reduction of the piston speed close to both dead centers, gives better conditions for the combustion processes, and thus a higher efficiency.Since the single cylinder-double piston with cycloid crank rotor displays better performance and reduced size compared to conventional combustion engines, it is believed that this new patented Swedish engine will compete with conventional engines in lawn movers, chain saws, outboard motors and other engines in similar small-scaled equipment.