Torque converter with narrowed flow passages

A hydraulic torque converter which comprises an impeller, a stator, and a turbine, each of which is provided with vanes, wherein the space through which fluid circulates is of the form of the space between an inner and an outer torus which are coaxial, wherein a section through the toruses by a plane containing their axis consists of an annulus which is defined by an inner closed curve provided by the intersection of the plane and the inner torus and an outer closed curve provided by the intersection of the plane and the outer torus, wherein the dimension parallel to the axis of the toruses of the outer closed curve is smaller than its dimension in the direction perpendicular to this axis, and wherein, considering a circle inscribed between the inner and outer closed curves and touching both of them and passing round the annulus, the value which is the product of the radius of such a circle and the distance of its center from the axis of the toruses alters, as the center of the circle passes around at least the portion of the annulus which corresponds to the turbine, from a maximum value at the inlet of the turbine to a minimum value which is substantially smaller than this maximum value.