The　maximum　potential　of　a　dual-loop　organic　Rankine　cycle　(ORC)　applied　to　a　light-duty　diesel　engine　is　analyzed　over　the　engine＇s　operational　range　by　developing　a　mathematical　model　based　on　physical　processes　and　boundary　conditions　specified　according　to　measured　data　from　an　engine　test.　We　further　evaluate　the　effects　of　three　working　parameters-expander　isentropic　efficiency,　evaporation　pressure　of　the　high-temperature　loop,　and　condensation　temperature　of　the　low-temperature　loop-on　the　performance　of　the　dual-loop　ORC　system.　The　results　show　that　using　the　proposed　dual-loop　ORC　system　improves　the　net　power　output　of　a　diesel　automotive　engine　by　19-22%　in　the　peak　thermal-efficiency　region　under　allowable　working　conditions　of　the　engine,　and　by　53-72%　in　the　high-speed　and　low-load　regions.　Over　the　engine＇s　entire　operational　range,　the　effective　thermal　efficiency　increases　by　a　maximum　of　8%.　Moreover,　the　expander　isentropic　efficiency　and　the　condensation　temperature　of　the　low-temperature　loop　are　two　critical　parameters　that　affect　combined　system　performance.　(C)　2014　Elsevier　Ltd.　All　rights　reserved.