Abstract: An Internal combustion engine is provided having separately designated combustion and exhaust powered cylinders, for implementing a dual exhaust expansion system which derives additional power from the combustion exhaust gases of each cylinder. The piston in each combustion exhaust cylinder is timed such that one leads the other by approximately 0-180 degrees crankshaft angle. Ignition of a first combustible air/fuel mixture produces combustion gases. Expansion of the combustion gases drives the first combustion piston during a first power stroke. Combustion gases are expelled from the cylinder to a second cylinder via fluidic passage to produce a second power stroke in the second cylinder, from there the combustion gasses are exhausted to atmosphere. Ignition of a second combustible air/fuel mixture produces combustion gases. Expansion of the combustion gases drives the second combustion piston during a third power stroke.