SOCIETY OFAUTOMOTIVE ENGINEERS, INC. TwoPennsylvania Plaza,NewYork,N.Y.10001 DieselEngineandHighway TruckNoiseReduction RoyM.Law DetroitDieselAllisonDiv.,GeneralMotorsCorp. International Automotive Engineering Congress Detroit,Mich. January8-12.1973730240 Downloaded from SAE International by Imperial College London, Monday, September 24, 2018©SOCIETY OFAUTOMOTIVE ENGINEERS, INC.,1973 Downloaded from SAE International by Imperial College London, Monday, September 24, 2018730240 DieselEngineandHighway TruckNoiseReduction RoyM.Law DetroitDieselAllisonDiv.,GeneralMotorsCorp. AFORMAL NOISEREDUCTION PROGRAM hasbeen established atDetroitDieselAllisonDiv.ofGeneralMotors Corp.inordertolearntheproblems anddevelopsolutions sothatdieselenginepoweredequipment canmeetthere quirements ofnoiselegislation. Previously, majornoiseproj ectsforthedivisionwererelatedtoproductimprovements or customer requestsandwerehandledbytheGeneralMotors ProvingGround(G.M.P.G.) NoiseandVibration Laboratories. Atechnical bulletin"NoiseMeasurement andControlfor DetroitDieselEngineApplications" waspublished in1967, revisedin1968,andrewrittenin1972(1)*.Thispresenta tionwilldiscussthebasicenginenoisereduction andthe highwaytrucknoisereductions. BASICENGINE NOISEPROGRAM Alargeperformance testcellwasmodifiedforbasicen ginenoisestudies.An8V-71engineisillustrated inthetest cell(Fig.1).Anelaborateexhaustsystemwasinstalled toeliminate mostoftheexhaustnoise.Airintakenoise wasreducedwithalargeoilbathaircleanerhavingacous ticaltreatment onthecleanerandtheairinletpipes. Coolingfannoisewaseliminated byusingawaterheatex changertomaintainenginewatertemperature. Enginestobe testedaremountedonisolationtypemountswithatorsion allysoftdriveshafttoconnectthetransmission tothedy namometer. Thetransmission isacoustically treatedto minimize noisefromthissource.Thedefinition for"basicenginenoise"isthemechanical orradiatednoisefromtheengine.Thecoolingfan,airintake, andexhaustnoiseisnotincluded. Thebasicenginenoisere ductionprogramhasincluded:enginemodifications, covers andpanels,totalcovers,andenclosures. ENGINEMODIFICATION -Attempts atenginenoisere ductionbyenginemodification withnoacousticaltreat mentshavebeendiscouraging (Fig.2).Oneprogramatthe G.M.P.G. NoiseandVibration Laboratories evaluated allof thecomponents ofanin-line4-71engine.Someofthecom ponentsandthemodifications madetothemwillbedis cussed(Fig.3.) Thepistonandlinerclearance wasreducedbytheuseof teflonbuttonsonthesidesofthepiston.Thepiston-piston pinandupperconnecting rodjointclearances werereduced andhigherpressurelubricating oilwassupplied. Theconnect ingrod-to-crankshaft clearances werealsodecreased andthey werealsosuppliedwithhigherpressurelubricating oil.The production spurgear-typeoilpumpwasreplacedbyalarge screw-type oilpumptoreducethepumpnoiselevel.A nylonidlergearwasalsousedtoreducethepumpgearnoise. Thereargeartrainoftheenginewasreplacedwithacog belttoeliminate gearnoise.Thisbeltwasunusualinthat therewerecogsoneachsideofthebelt.Thecogsonboth sideswerenecessarytodrivetheblowersandtosynchronize thecamshaftandbalanceshaftsproperlywitheachotherand thecrankshaft. Hydraulic valvelifterswereinstalledtoreduce thevalvemechanism noise.Pilotinjectorswereusedtore ducethecombustion noiseexcitation. Afinalefforttore ducethevibration ornoiseradiatingfromthelowersection ofthecylinderblockwastoseparatethemainbearingwebs*Numbers inparentheses designateReferences atendof paper. ABSTRACT ThispaperpresentstheresultsoftheDetroitDieselAllison basicenginenoisereductionprogramandthenoiseevaluationofaseriesofhighwaytrucks.Prediction ofnoisesource levelsandrecommendations tomeetvariouslegislative levels aresummarized. Downloaded from SAE International by Imperial College London, Monday, September 24, 20182 fromthelowersectionsofthecylinderblocks.Thecomplete modification oftheengineasdescribedresultedinlessthan 4dBAnoisereduction whenmeasured at6ftfromtheengine. Severalothercomponent modification investigations cover ingseveralenginemodelshaveresu