A compound engine assembly comprising: an engine core including at least one internal combustion engine, each internal combustion engine defining an internal cavity and including a rotor sealingly and rotationally received within the internal cavity to provide rotating chambers of variable volume in the internal cavity, the volume of each of the rotating chambers varying between a minimum volume and a maximum volume with a difference between the maximum and minimum volumes defining a displacement volume Vd, each internal combustion engine having an inlet port and an exhaust port in communication with the internal cavity; a turbine configured as an impulse turbine having a pressure based reaction ratio of at most 0.25, the turbine including a rotor including a circumferential array of rotor blades extending across a flow path; and an exhaust pipe for each internal combustion engine, each exhaust pipe having a pipe volume Vp, each exhaust pipe providing fluid communication between the exhaust port of a respective one of the at least one internal combustion engine and the flow path of the turbine, characterised by: each exhaust pipe terminating in a nozzle communicating with a portion of the flow path located upstream of the rotor blades; wherein for each exhaust pipe, a ratio Vp/Vd between the pipe volume Vp and the displacement volume Vd of the respective one of the at least one internal combustion engine is at most 1.5; and wherein a minimum value of a cross-sectional area of each exhaust pipe is defined at the nozzle. an engine core including at least one internal combustion engine, each internal combustion engine defining an internal cavity and including a rotor sealingly and rotationally received within the internal cavity to provide rotating chambers of variable volume in the internal cavity, the volume of each of the rotating chambers varying between a minimum volume and a maximum volume with a difference between the maximum and minimum volumes defining a displacement volume Vd, each internal combustion engine having an inlet port and an exhaust port in communication with the internal cavity; a turbine configured as an impulse turbine having a pressure based reaction ratio of at most 0.25, the turbine including a rotor including a circumferential array of rotor blades extending across a flow path; and an exhaust pipe for each internal combustion engine, each exhaust pipe having a pipe volume Vp, each exhaust pipe providing fluid communication between the exhaust port of a respective one of the at least one internal combustion engine and the flow path of the turbine, characterised by: each exhaust pipe terminating in a nozzle communicating with a portion of the flow path located upstream of the rotor blades; wherein for each exhaust pipe, a ratio Vp/Vd between the pipe volume Vp and the displacement volume Vd of the respective one of the at least one internal combustion engine is at most 1.5; and wherein a minimum value of a cross-sectional area of each exhaust pipe is defined at the nozzle. each exhaust pipe terminating in a nozzle communicating with a portion of the flow path located upstream of the rotor blades; wherein for each exhaust pipe, a ratio Vp/Vd between the pipe volume Vp and the displacement volume Vd of the respective one of the at least one internal combustion engine is at most 1.5; and wherein a minimum value of a cross-sectional area of each exhaust pipe is defined at the nozzle.