This　paper　proposed　a　new　combustion　strategy　for　the　spark-ignited　(SI)　engines.　A　gasoline　engine　was　converted　into　a　hybrid　hydrogen-gasoline　engine　(HHGE)　by　adding　a　hydrogen　injection　system　and　a　hybrid　electronic　control　unit.　Different　from　the　conventional　gasoline　and　hydrogen-enriched　gasoline　engines,　the　HHGE　is　fueled　with　the　pure　hydrogen　at　cold　start　to　produce　almost　zero　emissions,　with　the　hydrogen-gasoline　blends　at　idle　and　part　loads　to　further　improve　thermal　efficiency　and　reduce　emissions,　and　with　the　pure　gasoline　to　ensure　the　engine　power　output　at　high　loads.　Because　the　HHGE　is　fueled　with　the　pure　gasoline　at　high　loads　and　speeds,　experiments　are　only　conducted　at　clod　start,　idle　and　part　load　conditions.　Since　lean　combustion　avails　the　further　improvement　of　the　engine　performance,　the　HHGE　was　fueled　with　the　lean　mixtures　in　all　tests.　The　experimental　results　showed　that　the　hybrid　hydrogen-gasoline　engine　was　started　successfully　with　the　pure　hydrogen,　which　produced　94.7%　and　99.5%　reductions　in　HC　and　CO　emissions　within　100　s　from　the　onset　of　the　cold　start,　compared　with　the　original　gasoline　engine.　At　an　excess　air　ratio　of　1.37　and　idle　conditions,　indicated　thermal　efficiency　of　the　3%　hydrogen-blended　gasoline　engine　was　46.3%　higher　than　that　of　the　original　engine.　Moreover,　the　engine　cyclic　variation　was　eased,　combustion　duration　was　shortened　and　HC.　CO　and　NOx　emissions　were　effectively　reduced　for　the　hybrid　hydrogen-gasoline　engines.　(C)　2011　Elsevier　Ltd.　All　rights　reserved.