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ENGINETHEGASOLINEANDDIESELENGINEARETHEONESUSEDINTHEAUTOMOBILETODAYTHEGASOLINEENGINEISSTILLTHEMOSTPOPULARFORMTHEGASOLINEENGINEISAFOURSTROKE,SPARKIGNITIONENGINEITCANBEEITHERLIQUIDCOOLEDORAIRCOOLEDTHEREMUSTBETHERIGHTAIRANDFUELMIXTUREFORENGINECOMBUSTIONTHEAIRFUELMIXTUREMUSTBEIGNITEDATTHECORRECTTIMETHEAUTOMOBILEENGINEISUSUALLYAFOURSTROKEENGINETHATIS,THEREAREINTAKE,COMPRESSION,EXPANSIONALSOCALLEDPOWERANDEXHAUSTSTROKESFORAGASOLINEENGINE,THEINTAKESTROKEBRINGSTHEFRESHAIRANDFUELTHECOMPRESSIONSTROKECOMPRESSESTHEAIRFUELMIXTUREWHENTHEMIXTUREISIGNITEDBYSPARKPLUGS,THEEXPANSIONTAKESPLACETHEEXPANDINGGASESPUSHDOWNONTHETOPOFTHEPISTON,THEPOWERSTROKEOCCURSASTHEPISTONCOMESUPAGAINEXHAUSTGASESAREPUSHEDOUTOFTHEENGINE,THEEXHAUSTSTROKEHAPPENSENGINELUBRICATIONSYSTEMFUNCTIONANDCOMPONENTSOFENGINELUBRICATIONSYSTEMTHEREAREAGREATMANYMOVINGMETALPARTSINTHEENGINETHESEPARTSMUSTBEPROTECTEDBYLUBRICATINGOILSOTHATTHEREWILLBENOACTUALMETALTOMETALCONTACTTHEMOVINGPARTS,INNATURE,FLOATONFILMSOFOILTHELUBRICATINGOILCIRCULATINGTHROUGHTHEENGINETOALLMOVINGPARTSREQUIRINGLUBRICATIONPERFORMSOTHERJOBS1LUBRICATEMOVINGPARTSTOMINIMIZEWEAR2LUBRICATEMOVINGPARTSTOMINIMIZEPOWERLOSSFROMFRICTION3REMOVEHEATFROMENGINEPARTSBYACTINGASACOOLINGAGENT4ABSORBSHOCKSBETWEENBEARINGSANDOTHERENGINEPARTS,THUSREDUCINGENGINENOISEANDEXTENDINGENGINELIFE5FORMAGOODSEALBETWEENPISTONRINGSANDCYLINDERWALLS6ACTASACLEANINGAGENT,WASHINGTHEWORKINGSURFACESFREEOFCHEMICALDEPOSITS,DUSTANDDIRTTOPROTECTTHEMFROMCORROSIONTHEMAINPARTSOFALUBRICATIONSYSTEMAREPUMP,MAINOILGALLERY,RELIEFVALVEANDFILTERSLUBRICATINGOILASATISFACTORYENGINELUBRICATINGOILMUSTHAVECERTAINCHARACTERISTICS,ORPROPERTIESITMUSTHAVEPROPERVISCOSITYBODYANDFLUIDITYANDMUSTRESISTOXIDATION,CARBONFORMATION,CORROSION,RUST,EXTREMEPRESSURES,ANDFOAMINGALSO,ITMUSTCATASAGOODCLEANINGAGENT,MUSTPOURATLOWTEMPERATURES,ANDMUSTHAVEGOODVISCOSITYATEXTREMESOFHIGHANDLOWTEMPERATUREANYMINERALOIL,BYITSELF,DOESNOTHAVEALLTHESEPROPERTIES,LUBRICATINGOILMANUFACTURERSTHEREFOREPUTANUMBEROFADDITIVESINTOTHEOILDURINGTHEMANUFACTURINGPROCESSTHEOILFORSEVERESERVICEMAYHAVEMANYADDITIVES,ASFOLLOWS1USUALLYAVISCOSITYINDEXIMPROVER2POURPOINTDEPRESSANTS3OXIDATIONINHIBITORS4CORROSIONINHIBITORS5RUSTINHIBITORS6FOAMINHIBITORS7DETERGENTDISPERSANTS8EXTREMEPRESSUREAGENTSMETHODOFLUBRICATIONTWOTYPESOFLUBRICATINGSYSTEMSHAVEBEENUSEDONFOURCYCLEAUTOMOTIVEENGINES,SPLASHANDCOMBINATIONSPLASHANDPRESSUREFEEDINTHESPLASHLUBRICATINGSYSTEM,OILISSPLASHEDUPFROMTHEOILPANOROILTRAYSINTHELOWERPANOFTHECRANKCASETHEOILISTHROWNUPWARDASDROPLETSORFINEMISTANDPROVIDESADEQUATELUBRICATIONTOVALVEMECHANISMS,PISTONPINS,CYLINDERWALLS,ANDPISTONRINGSINTHECOMBINATIONSPLASHANDPRESSUREFEEDLUBRICATINGSYSTEM,ANOILPUMPTAKESOILFROMTHEOILPANANDFORCESITTHROUGHHOLESDRILLEDINTHEENGINEBLOCKANDCRANKSHAFTTHISOILTHEREBYREACHESTHEVARIOUSBEARINGSTHATSUPPORTROTATINGSHAFTSANDTHEDIFFERENTMOVINGPARTSINTHEENGINEITCOVERSTHESURFACESOFTHEMOVINGPARTSTOPREVENTMETALTOMETALCONTACTANDUNDUEWEAROFTHEPARTSINTHISSYSTEM,CYLINDERWALLSARELUBRICATEDBYSPLASHINGOILTHROWNOFFFROMTHECONNECTINGRODBEARINGSENGINECOOLINGSYSTEMFUNCTIONANDVARIETYOFENGINECOOLINGSYSTEMTHEPURPOSEOFTHECOOLINGSYSTEMISTOKEEPTHEENGINEATITSMOSTEFFICIENTOPERATINGTEMPERATUREATALLENGINESPEEDSUNDERALLDRIVINGCONDITIONSASFUELISBURNEDINTHEENGINE,ABOUTONETHIRDOFTHEHEATENERGYINTHEFUELISCONVERTEDINTOPOWERANOTHERTHIRDGOESOUTTHROUGHTHEEXHAUSTPIPEUNUSED,ANDTHEREMAININGTHIRDMUSTBEHANDLEDBYTHECOOLINGSYSTEMTHISMEANSTHATTHEENGINECANWORKEFFECTIVELYONLYWHENTHEHEATENERGYISEQUALLYHANDLEDSOASTOKEEPTHEENGINETEMPERATUREINBALANCESO,THETEMPERATUREISQUITEESSENTIALFORANENGINETOPRODUCEPOWERIFTHEENGINERUNSTOOHOT,ITMAYSUFFERFROMPREIGNITIONVISCOSITYOFTHEOILISREDUCEDHCEMISSIONISINCREASEDTHISALSOCAUSESPOORPERFORMANCEANDPREMATUREWEAR,ANDMAYEVENRESULTINENGINEDAMAGEWHATSMORE,UNDERTHISCONDITIONTHEMETALDEFORMSSLOWLYANDCONTINUOUSLYIFTHEENGINERUNSTOOCOLD,THEFUELWILLNOTVAPORIZEPROPERLYIFLIQUIDFUELREACHESTHECYLINDERS,ITWILLREDUCELUBRICATIONBYWASHINGTHEOILFROMTHECYLINDERWALLSANDDILUTINGTHEENGINEOILTHISCAUSESALOSSOFPERFORMANCE,ANDINCREASEINHCEMISSIONS,ANDPREMATUREENGINEWEARFORTHESEREASONS,ACOOLINGSYSTEMOFSOMEKINDISNECESSARYINANYINTERNALCOMBUSTIONENGINETHEREAREGENERALLYTWODIFFERENTTYPESOFCOOLINGSYSTEMWATERCOOLINGSYSTEMANDAIRCOOLINGSYSTEMWATERCOOLINGSYSTEMISMORECOMMONCOMPONENTSOFENGINECOOLINGSYSTEMAWATERCOOLINGSYSTEMCONSISTSOFTHEENGINEWATERJACKET,THERMOSTAT,WATERPUMP,RADIATOR,RADIATORCAP,FAN，FANDRIVEBELTANDNECESSARYHOSESAWATERCOOLINGSYSTEMMEANSTHATWATERISUSEDASACOOLINGAGENTTOCIRCULATETHROUGHTHEENGINETOABSORBTHEHEATANDCARRYITTOTHERADIATORFORDISPOSALTHEENGINEISCOOLEDMAINLYTHROUGHHEATTRANSFERANDHEATDISSIPATIONTHEHEATGENERATEDBYTHEMIXTUREBURNEDINTHEENGINEMUSTBETRANSFERREDFROMTHEIRONORALUMINUMCYLINDERTOTHEWATERINTHEWATERJACKETTHEOUTSIDEOFTHEWATERJACKETDISSIPATESSOMEOFTHEHEATTOTHEAIRSURROUNDINGIT,BUTMOSTOFTHEHEATISCARRIEDBYTHECOOLINGWATERTOTHERADIATORFORDISSIPATIONANAIRCOOLINGSYSTEMCONTAINSACENTRIFUGALFAN,THERMOSTAT,FANDRIVEBELT,RADIATORFINS,BAFFLEPLATES,AIRCONTROLRING,ETCANAIRCOOLINGSYSTEMMEANSTHATAIRISUSEDASACOOLINGAGENTTOCIRCULATETHROUGHTHEENGINETOCARRYTHEHE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就是说，进气行程、压缩行程、作功行程和排气行程。进气行程带来了新鲜的空气燃料。压缩行程将可燃混合气压缩。当这种混合气被火花塞点燃，气体开始膨胀。膨胀的气体推动活塞的顶部向下运动，作功行程就开始了。当活塞向上运动时，废气被排出发动机，这一过程被称为排气行程。发动机润滑系统润滑系统的作用及组成发动机中有大量的运动的金属零件。要保护这些零件就必须进行润滑，这样可以避免金属零件之间的直接接触。实际上，在运动零件的表面总是覆盖着一层油膜。润滑油在发动机的所有活动部件之间循环流动，其作用为1润滑运动零件，减少磨损。2润滑运动零件，减少因摩擦引起的功率损耗。3起冷却剂作用，带走发动机零件产生的热量。4吸收轴承和其他发动机零件之间产生的冲击力，减少发动机的噪音，并延长其寿命。5在活塞环和气缸壁之间形成良好的密封。6起清洁剂作用，冲洗运动零件表面的化学杂质、灰尘和污物，以避免部件受到腐蚀。润滑系统的主要组成部分有机油泵、主油道、限压阀和滤清器。润滑剂理想的发动机润滑油必须具有某些特性必须具有一定的粘性粘稠度和流动性，并且必须具有抗氧化、防止碳膜生成、防腐、防锈、抗极压和防泡沫等作用，润滑油必须具有良好清洁作用和良好的低温流动性，以及在高温和低温时都具有良好的粘性。任何矿物油自身都不具备所有这些特性。因此，润滑油厂家在制造润滑油的过程中，加入了许多添加剂。高级润滑油中可能加入以下这些添加剂1常常加入黏度指数添加剂；2抗凝剂；3抗氧剂；4防腐剂；5防锈剂；6抗泡剂；7净化分散剂；8极压剂。润滑方式四冲程发动机使用两种润滑系统飞溅式润滑和飞溅压力结合送油式润滑。在飞溅润滑系统中，油从机体下部的油盘或油底壳中飞溅上来。飞溅上来的的油形式油滴或油雾，使气门机构、活塞销、气缸壁和活塞环得到充分的润滑。在飞溅压力结合送油润滑系统中，油泵从油盘中把油抽上来并压入发动机机体上和曲轴上的油道，被输送到发动机的曲轴和各种运动零件的每个轴承上。润滑油在运动零件表面形成油膜，以防止金属零件表面直接接触以及零件的过度磨损。在这一系统中，气缸壁是由边杆轴承运动飞溅起来的油进行润滑的。发动机冷却系统冷却系统的作用和分类冷却系统的作用是在任何的驾驶环境中，在任何的发动机转速下保持发动机处在最有效的工作温度下。当燃油在发动机内燃烧时，大约1/3的热能转化成了动力，1/3的被排气管散发掉，还有1/3必须由冷却系统来处理。也就是说只有当产生的能量和处不景气能量相等时，发动机温度才能处在平衡状态，发动机才能正常工作。那么，对于提供动力的发动机来说，温度是最基本的要素。假如发动机太热，那可能造成点火提前、润滑油的粘性降低、碳氢化合物的排放增加。这样，性能低下，磨损加剧，甚至使发动机损毁。再说，在这种条件下，金属会慢慢地变形。若冷却过度，燃油将不能完全雾化，假如液态燃油进入气缸，它会冲掉气缸壁和发动机的机油从而导致润滑减少，这就造成性能低下，碳氢化合物排放增加，磨损加剧。基于以上原因，冷却系统在任何内燃机上都是必需的。冷却系统通常有两种不同的类型水冷却系和风冷却系，水冷却系比较常见。冷却系统的组成水冷却系统包括水套、节温器、水泵、散热器、散热器盖、风扇、风扇带和橡胶软管。水冷却系是把水作为冷却的介质，通过发动机内的水循环来吸收热量，然后把它送到散热器去散热。发动机主要是通过传递和热挥发来冷却的。发动机中可燃混合气燃烧所产生的热量必须从铁制或铝制的气缸中传送到冷却里的冷却水中。在冷却水套的外面一部分的热量散发到了空气中，但大部分的热量通过冷却水被传送到散热器中散掉。风冷却系包括离心式风扇、节温器、风扇带、散热片、板、节气阀等。风冷却系是把空气作为冷却的介质，通过发动机内的空气循环来带走工作零件的热量。当发动机工作时，强力的空气吹过散热片带走了热量。快热是风冷发动机的特性，因为它们没有热水在水套和散热器里。冷却液冷却媒介或者散热剂，包括冷却水和一些防冻液，被称为冷却液。那是对添加到冷却系统中的冷却水在低温下凝结成冰问题的解决方法实际的凝结温度是由添加到系统中的冷却液的质量业决定的，当温度降低时，冰的体积会增加，那么假如防冻液凝结的