Abstract: A rotary engine contains a laterally displaceable rotary member which is sealably and slidably engaged by a rotor plate which has been modified for sealing, travels in an eccentric circle along with the rotor, but provides sealing against the rotor using corner seals and surface seals, and is also further sealed against the engine housing so that combustion gasses in the vicinity of the rotor and rotor plate do not escape either between the rotor and rotor plate surfaces nor between the rotor plate surfaces and the engine housing surfaces. The other end of the rotor rotatably depends from a reducing piston which is sealably engaged against the internal portion of the engine so that it can travel laterally, in order to laterally displace the rotor. During engine operation, the rotor can be made to be axially displaced or pushed through the rotor plate to lower the effective combustion volume.