A Wankel rotary engine produced by Advanced Innovative Engineering (AIE) UK Ltd with a capacity of 225cc is investigated, employing a rotary expander as an energy recovery system, aiming at maximizing the expansion of the gas and improving the overall efficiency of this propulsive system. In this configuration, the expander is placed alongside to the engine and receives exhaust gas from the engine by means of a short and straight connecting pipe. Unlike the engine, the expander has a Wankel-type 1:2 configuration. A thorough description of the machine, including the main mechanical, kinematic and port-timing parameters are reported, in addition to details of the test rig and experimental methodologies adopted. Finally, this work presents the experimental results obtained from the engine equipped with the expander and compares those results with the engine baseline performance.