Maximum efficiency of cyclic combustion engines (CCE) is achieved when using stratified charge and high compression ratio with controlled air circulation and combustion. A description is given of a varying-area, toroidal-shaped combustion chamber designed to achieve the above objectives by: obtaining initial circulatory air motion induced by the piston late in the compression stroke; increasing this piston-induced velocity using the momentum of fuel injected tangentially to the center line of the toroid; and by using combustion to further increase the circulation rate. Four combustion chamber configurations were studied in a bomb with zero initial air velocity to ascertain whether significant rotation could be achieved by injection and combustion. Gas pressure was measured and high speed photographs were taken of the injection and combustion process. The ideal situation, at full load, is to have one rotation of the gas during the time allocated to combustion. The experimental results, with zero initial velocity, show that fuel momentum plus combustion produces from one-half to three-quarters of a rotation in the available time. Modeling suggests that the use of initial, piston-induced velocities would result in the desired one rotation in the available time.