An internal combustion engine arrangement comprising: - at least one combustion cylinder; - a first and a second expansion cylinder, each of the first and second expansion cylinders being arranged in downstream fluid communication with the at least one combustion cylinder for receiving combusted exhaust gas via a respective inlet valve (303, 305) of the first and second expansion cylinders; wherein the internal combustion engine arrangement comprises an interconnection conduit between an outlet of the first expansion cylinder and an outlet of the second expansion cylinder, and an engine aftertreatment system, the engine aftertreatment system being arranged in fluid communication with the interconnection conduit, characterized in that the outlet of the first expansion cylinder is further arranged in fluid communication with an exhaust gas recirculation conduit for delivery of a flow of combusted exhaust gas to an intake passage of the internal combustion engine arrangement, and wherein the second expansion cylinder comprises a reducing agent injection device for controllably delivery of a reducing agent into the second expansion cylinder, wherein the interconnection conduit comprises a void volume comprising a flow restriction arrangement for reducing the flow turbulence within the void volume, the EGR conduit being connected to the interconnection conduit at a position between the outlet of the first expansion cylinder and the void volume of the interconnection conduit, and wherein the engine aftertreatment system is connected to the interconnection conduit at a position between the void volume and the outlet of the second expansion cylinder. - at least one combustion cylinder; - a first and a second expansion cylinder, each of the first and second expansion cylinders being arranged in downstream fluid communication with the at least one combustion cylinder for receiving combusted exhaust gas via a respective inlet valve (303, 305) of the first and second expansion cylinders; wherein the internal combustion engine arrangement comprises an interconnection conduit between an outlet of the first expansion cylinder and an outlet of the second expansion cylinder, and an engine aftertreatment system, the engine aftertreatment system being arranged in fluid communication with the interconnection conduit, characterized in that the outlet of the first expansion cylinder is further arranged in fluid communication with an exhaust gas recirculation conduit for delivery of a flow of combusted exhaust gas to an intake passage of the internal combustion engine arrangement, and wherein the second expansion cylinder comprises a reducing agent injection device for controllably delivery of a reducing agent into the second expansion cylinder, wherein the interconnection conduit comprises a void volume comprising a flow restriction arrangement for reducing the flow turbulence within the void volume, the EGR conduit being connected to the interconnection conduit at a position between the outlet of the first expansion cylinder and the void volume of the interconnection conduit, and wherein the engine aftertreatment system is connected to the interconnection conduit at a position between the void volume and the outlet of the second expansion cylinder.