Abstract: An internal combustion engine is described as having a unique angular relationship between the longitudinal axis of each piston cylinder, the center axis of any associated intake ports through which fluid enters the cylinder, and the longitudinal axis of any associated intake passageway for channeling fluid to the communicating intake port, to induce the fluid entering the cylinder to swirl about an axis which is angularly disposed to the longitudinal axis of the cylinder, rather than conventionally swirling about the longitudinal axis of the cylinder. The initial velocity of swirl is then accelerated by the principle of conservation of angular momentum to a more rapid and robust velocity during the compression stroke, thereby allowing the use of a much leaner fuel to air mixture.