A　493　diesel　engine　is　supercharged　by　a　pressure-wave　supercharger　(PWS).　Improving　the　power　of　the　PWS　diesel　engine　the　grey　relational　analysis,　which　focused　on　the　experimental　results　of　the　diesel　engine,　was　completed.　The　analysis　results　show　that　two　factors,　the　intake　air　flow　and　the　exhaust　temperature,　have　the　most　important　influence　on　the　PWS　diesel　engine.　At　the　suggestion　of　the　grey　relational　analysis　the　volume　of　the　intake　manifold　is　increased　to　allow　more　intake　air　flow　while　the　exhaust　manifold　is　wrapped　by　asbestos　with　an　iron　cover　to　preserve　the　high　exhaust　temperature.　The　final　experimental　results　after　those　changes　show　that　both　the　power　and　the　torque　have　been　build　up　as　well　as　the　NOx　emission　has　been　reduced　effectively.