The　effect　of　common　rail　system＇s　injection　timing　and　rail　pressure　on　high-power　diesel＇s　fuel　economy　and　emission　characteristics　has　been　studied　through　tests.　The　experimental　results　show　that　with　the　rail　pressure　increasing,　fuel　economy　and　smoke　are　improving,　while　NOx　is　deteriorating.　However,　as　rail　pressure　very　high,　the　improving　trends　of　smoke　and　fuel　economy　are　not　obvious　terribly,　and　even　at　low　load　condition,　the　economy　will　decline　instead.　With　injection　timing　delayed,　NOx　is　reducing　while　smoke　and　fuel　economy　are　augmenting　at　the　conditions　of　high　load.　However,　at　the　low　load　conditions,　with　injection　timing　lagging,　smoke　and　NOx　will　decline　simultaneously.　(C)　2011　Published　by　Elsevier　Ltd.　B.V.　Selection　and/or　peer-review　under　responsibility　of　International　Materials　Science　Society.