Abstract: An internal combustion engine having two separate main combustion chambers isolated from the cylinder and from each other by means of a valve throttle mechanism. Combustion occurs first in one chamber, and then in the other, separated by one complete revolution of the crankshaft in the two-cycle embodiment and two complete revolutions of the crankshaft in the four-cycle embodiment. The alternative operation effectively removes the combustion process from the cycle for a sufficient amount of time to enable the combustive reactions to approach chemical equilibrium prior to release in the cylinder.