A moving wall positive displacement turbine system, or moving wall engine, utilizes the relative rotation of a ring, a central body, and a housing with respect to each other to generate power, where the ring is concentrically positioned in a channel between the central body and the housing. The housing and central body remain stationary while the ring rotates within the channel. The channel has low friction walls on either side to reduce friction between rotating components. The ring has a series of vanes passing through it and pivotally attached on each side to the low friction walls in the housing to compress an air-fuel mixture prior to combustion. The system is able to compress and combust an air-fuel mixture to generate direct rotational energy.