BMEP of gasoline engine level has been achieved under NOx-free and non-backfire by using retarded intakevalve timing and lean-boosting for hydrogen fueled research engine with external mixture in previous research. Since itis lower than that of typical commercial gasoline engine, available maximum output in the area of NOx-free wasinvestigated with higher lean boosting pressure. As results, it was confirmed that more than 10bar BMEP(level ofconventional gasoline engine) was possible without NOx and backfire by the above strategies. This value of 10.6barwas obtained under operating condition of boost pressure 2.4bar and Φ=0.35.