<div class="section abstract"><div class="htmlview paragraph">Recently, waste heat recovery system from automobile exhaust gas has attracted a lot of attention as one of the promising technology to improve fuel efficiency and to reduce carbon dioxide emission. In order to put this system into practice, we developed a novel liquid-piston steam engine which has large potential of high efficiency, high reliability and low cost. Thermal efficiency of 12.7 % is achieved at temperatures of <i>T_h</i> = 270 °C and _<i>l</i> = 80 °C. Finally, electrical output of waste heat recovery system with the liquid-piston steam engine is estimated to be 44 or 79Wh under NEDC or HWFET modes, respectively.</div></div>