Abstract: A piston for an internal combustion engine. The piston has upper and lower compression rings and a recess between the two which exposes a greater proportion of the ring end gap for the lower compression ring. As a result, the space between the rings and below the lower compression ring provides a capacitance volume to minimize top ring reversal.

Abstract: A housing surrounds a rotatable turbine wheel having an axis of rotation and effects a uniform fluid wheel boarding state. The housing includes at least one elongated substantially spiral passageway which encompasses the periphery of the wheel. The passageway has an external peripheral fluid inlet and an internal fluid outlet, the latter encompassing the wheel periphery. The passageway is defined by a pair of opposed axisymmetrical side walls having an inner diameter proximate the periphery of said turbine wheel. An outer wall extends between the two side walls circumferentially around at least 360.degree. of the turbine axis. The radial location of the outer rail is defined by the path prescribed by the direction of fluid flow in a free vortex constrained by the side walls. Disposed within the passageway and extending substantially throughout same may be a multi-portion generally helical partition.