A　self-developed　electronic　control　system　was　used　to　adjust　hydrogen　and　gasoline　injection　durations.　The　hydrogen　volume　fraction　in　the　intake　(φH2)　is　increased　from　0%　to　6.5%.　For　a　specified　φH2,　gasoline　injection　duration　is　reduced　to　keep　the　excess　air　ratio　of　the　air-fuel　mixture　in　working　cylinders　at　the　stoichiometric　condition.　Cylinder　cutoff　was　realized　by　stopping　the　fuel　supply　to　the　specified　cylinders　through　the　electronic　control　unit.　The　test　results　demonstrated　that,　for　a　given　φH2,　engine　volumetric　efficiency　is　enhanced,　flame　development　and　propagation　periods　are　shortened,　the　coefficient　of　variation　in　engine　idle　speed　is　decreased,　and　pumping　loss　is　reduced　after　cylinder　cutoff.　Both　cylinder　cutoff　and　hydrogen　enrichment　are　effective　on　reducing　cooling　loss　and　engine　fuel　energy　consumption　at　idle.　At　φH2=6.63%　and　two-cylinders　cutoff　mode,　fuel　energy　flow　rate　is　decreased　by　about　40%,　compared　with　that　of　the　original　engine.