An air supply system for a reciprocating internal combustion engine includes an air inlet and a mixing volute for receiving charge air from the air inlet. The mixing volute is configured to impart swirl in a first direction to charge air passing from the air inlet and into the volute. An EGR injector introduces exhaust gas into charge air passing through the mixing volute, with the EGR injector being configured to impart swirl in a direction which is opposite to the swirl produced by the mixing volute. This causes the EGR gases and the charge air to become thoroughly mixed within a very short path length through the mixing volute.