A waste heat recovery system for a split-cycle engine includes a heat exchange unit. An air compressor device is in communication with the heat exchange unit. A waste heat input receives waste heat from the engine and is in fluid communication with the heat exchange unit. An ambient air intake connected to the air compressor device draws air into the air compressor device. A compressed air outlet member on the air compressor device in fluid communication with a compression cylinder of the split-cycle engine delivers compressed air from the air compressor device to the engine. Engine waste heat is communicated to the heat exchange unit and energy from the waste heat is used to drive the air compressor device, causing the air compressor device to draw in ambient air through the ambient air intake, compress the ambient air, and deliver compressed air to the engine through the compressed air outlet.