c.,pe. ,,( ,h,; "'" '" n'.1 y "" """'......,1 I"1m ",,1.,,:11... ",I k.,. ,',,""Iy(""n ,he:""bl"he:. hy ma, 1 'n", ""I>!,)"-ICm.'" ,,,,,,,,,,i,,,,,1,n ""y hm orhy ...y """...... """""....... .-h"",. 0,'.,n,. h:)I,j,,'f _ '"",he:.," ,..... """','" ,Ilt ,... n "'"''''"' 01the pu", ,,h,,,Tho>il1:VJt:oII"'flU!AU TlIOIiAS"IUIII ..SII >:11IV. Vt:lIt:f.N ... n Vls t:1lOF..." ... RTICII-LAUl'UUN1St:,"Nil t:Vt:S1rA""" 1'II;UI... KI' UIII'J ofpra sure.Note t hat for fhe turOO engine. mllX" mum preullre OCCll"* 01oboot 20- ATDC, yet only obinsuchraces.A street carwiththreemillionmil!!son ii may sC(!rnto be st retching the point, b\lltheideadoes n' tfailtoimpress. 1'0 stand along the banking ulDaytona when aPorsehe 962 turbo comeswhi stling byinelCcess of 200 mph can easily leave one llghast to think that these thing!> are goi ng to do this for twenty-four hours. The violence and speed can give ihe initiul impressionthat nobody will fi ni shthisrace.Yel,chnncesare aturbochargedrat-erwilltnke the checker first.This book is primllri!y nbout s treet turbocharging, not race cars, but the problems al'e the same, even ifdifferent in St reet CMS,by compar-ison, are a piece of cake. Chrysler even a70,OQO-mile warranty on some of its turbo cars. How du rability is uttuined is so easy to answer as is the questiOn of whetherit exists.InIIbrood !jense, durability boi ls downLot he control of heat inlhe engine/turbo sy8tem.EachIISpectof the systeminwhichheatplays n part is a candidil te for' the Achille!;' heel. For long-term dur'ability_ each ofthcsc factorsmust beoptirni;(cd.'I' heyincludetu rbocompressoreniciency,inter-cooling, t-ont rolor end-b'lIS temperatures, turbi nebearing temperatures,und muny others, and willbe discussedinthefollowingchapters. Weshould call the answer to the entire heat problem "thermal management. In reading this book,it willprm'Cusefullo keep uppermost in mindthat vi rtunllythe entire :;ucccss of aturboien,,lnebmep is all an average pressure pushing the piston down the bore. Listhelength of the stroke. This tells youhow fartheis going to push the piston. A is the area of the bore. This is, oJ"course, the area the prelSlSure has to work on. Nisthe number of putts the enblne is running and how many cylinders it h611. N .,- r,. d'pm ..7JU.IlLUI;I"Ocymersx2 (For a4-stroke engine,therpmis di vided by 2because each cylinderfires only on alternate revolutions.) Now, there are severnlinlere8tingrelationships here!"o r example, take the P and multiply bytht! Aand youhave apressul'e times an mea,whichisnoth-ing more complicated than the average fOl"(.'Cpushing down on the piston. Now mul tiply the PA(for(.-e)bythe length of the stroke, L (di stance),and youhave a number that represents the torque output of the cylinder.Then take this fig-ure lindmultiply bytht! N(how fast the job is getti ng dOne), and therclSult is Power,the thing we ure reaUyuftCI". Please note that lhis means Power ",torque )(rpm gas pressure r p"") _ _01bote I"A" -/ I 0 Lengll1 01 I Slroke ("'\.."' \ I \ --8CH APTER1:ANENGIN EERINGL OOKATTHEBASICS Driveability Limitations Ag.all " Iyp" ,al example of tilt differenceintorqll e cl,roes fOI'a turbo-charged alld all atmosphe1ic Since the whole purpose of this exercise is to get mQrepower, let'!) examine what this PLAN gives us tQ work with. First, let's check Qut what working wilh the N can yield. There are two ways to !,'t:tmore putts pel" minute; ndd more cylinders or \'ev the en!,>inc highcl".That leaves little to wot'kwith, as the whole field of endeavor known us blueprinting is almost solely for the purpose of allowing higher rpm with some degree ofsafe-ty.Consider that those nasty inertialloadlS go up with the !;Quare of the rpm in-crease, That meansthat ,1t7200rpm,the inertialloadwillbe144%groater thall at 6000rpm.Weal' andtear li es up there.Ultimately,it isneither cheap, pleasant,nor dumble long-term to increase power output byincreasing the N. Since we cannot, for practical reasons, increase power lSigllificllntlywith N, til!! onlyremaining choice is to increase torque by doing something with the PLA. Sowemust goback and look at the PLA abit more.Wecan change the A. Bored, it's calleeability? Ddveability of fuel-injectedwillremainthe same_Driveabilityof blow- t hrough carbureted engines will remain virtually the same. The starting of carbureted engincs will be degraded s lightly. Please note that draw-through unitswillvirtually always degrade driveabilityandstarting somewhat, with cold proving the Achilles'heel of a draw-thro\lgh system. Will/he l!ubocharger hurt my mileage? Yes.The turbo,wheninstalledas an aftermarket item on aspark-ibrnition engine, is not an economi:ter and cannot be construed as such. There isno en-gineeri ng basis for making such If you are led into purchasing n turbo under the premise of improving your fuelmi leab'C,besuretoget awritten b'U{unntee.Whennot operating under boost, aturboclwrgcr is asmall system restriction. This rest r iction CIIUWSasmall lossinvolumetric efficiency.Volu-metric efficiency and fuel economy are definitely tied together.If your driving habits are aboutthe same as most, your mileage willdrop aoout10% city and 5'l highway.No miracles here. Will the turbodwrger affect cngine wear and maintenance? Certainly the turbo will afi"ect engine wear. Do you really expect to add pow-er andnot increase wear? Nomiracles here either.If you drive vigorously but with some respect for the equipment, you can expect about goq of normnl en-gine life. Will the /rG/lSmi8Sion and drive/rain be adversely affected? Very unlikely. Consider that the ddvetrnin endures more torque infu-stgear from the stock engine than almost uny turbo can produce in second b'Ca.r.Occa-sionallyaclutch comes along that WOII '\ do the extra duty.Most clutchprob-lems nre going to crop up when shining hl.lbits nre less than acceptable. Not to worry. What cioes it feellike to drive a properl.v set up tl/rbo cor? A turbo can justifinblybecalled(Itorquemultiplier:themorcboost,the more torque. This situation is ttlgear ratioaFor example, athil'd ge{lr wilh tltranny r{ltio of L4 will dt'vdup 4!Y{mOre tOrt:]UI; at tht! rem- wheels lnOIl il fNld h-gcm' ruLio of 1.0. A boo!>tpre 'l;U re of 6 pUIii!increu:lCtorque by 14CHAPTER1:ANENGINEERINGLOOKATTHEBASICS aboul 40% (using an intercooler). Thus you(;8nsee lhat6 psiboostwillpro ducefourth.gearaccelerationvirtuallyequalto 8stockautomobi le'slhird gear capabiHly.I m a ~..ine what the proper turbo car willdo insecond gear! An-otherreasonablecomparisonisthat apropertul'l)()curoperating at10psi boost willdo 0-60 in twoth irds the original time; Le., 6 seconds versus 9 sec-onds. FlIf.21.The Mitsubishi 3000GT Iru-bochnrged 2 4 - u a l ~ VB. Two turlKui, two Itllercoo/l!'rtI. {orlNI,heel driw. o"d 183 cui giuethe 3000G'/' I'xtr(U}mi mrry poIelllraJ. ACQUIRINGA TURBOCHARGEDVEHICLE The essence of this book, if s uch exists, is to provide the performance car en-thusinst interesu.>dinlurhochaq,';ng with 11bodyof informationthat can be used to evaluate system designs, whether of a factory turbo sySl.em or an ufter-murket kit. This book is alSQintended as adesign guide for the hobbyist who wants to build his own turbocharger system. Three viable methods exist to ac-quire a turbochurgt.>d vehicle: buy an OEM-turbocharged automobile buy an aftermarket kit , if available, for your specific application build your ownturbo system The rationale behindthe decisionthat suits yournl,*->dsandrequirements best is no mot"t!than alogical su mmary of the foll owi ng: What is the intended use of the vehicle? Whut is the JCl;aJitywithrctlpect to slate and federallawand the year of the car? Howmuch powt!1"isrequired'! 19fearof afuilure such that afactorywarranty isrequired? Can youmake u reasonable judgment withfepcctt.othe engineering of an aftermarket. kit? Do you have the skills, time, patience, and equipment to build your own? 15 16CHAPTER2:ACQUIRINGATURBOCHARGEDVEHI CLE OEM Turbocharged Automobile Aftermarket Turbo Kit Automobile manufaCWrers have built a variety orturbo cars in the last decade. One can easily wonder how some decisions are made. On one hand we have the FordEXP Turbo, most Chryslers. andthe NissanNXTurbo. The otherhand holdssomething likethePorsche944,BuickGNX,IlndLotusEsprit turbo. Members of the radiCl\1middle are large innumber, relatively nondescript, and not entirely without mt!ri t . Inmost circumstances, the factory turbo engine is conservative in power nutput.--easily understandable inview of warranties, li-abilities,andemi!!SionHrequirements.Generallyspeaking,OEMswillnot equip 11turbochargur systemwith optimum-confil,'I.Ilationparts.Virtually all OEMdesigns willhave some shortcoming,whether inturbo size,intercooler capability,or restrictive exhnusts. Occasionally the shortcoming is just adif-ferentdesign,basedontheOEM'sperceptionof itsbuyers'requirements. Finding and fixing these weak li nksthen becomes the focus of attention in ef-forts at greater performance. Q' RULE: OEMs wilt generally provide you with a vehicle that functions nicely but isblessedwithenoughshortcomingsthat performance isfar from optilllUm. The first step inpurs\Ling morepelformance is u complete analysisof the system design.Chaptert4,Testing the System,isyour starting point.With those data accumulatedand analyzedandtheweaklinks identified,you can set out to findthe nectlSSilry components to improve the ljysltllll. Keep in mind that the issue here istoimprove efficiency,thereby opening upthepotential forhuge gains in power. Increasing boost pressure is also a consideration, but without efficiency improvements, this path to power isfraught with mechani-calrisk.Oncethe systemhasbeentestedandthe merit of eachfeaturehas been determined, start the improvement process with the weukest link. Here is where foresight becomes important.For example, nnintercooler that loses only 2 psi at the factory-ratoo boost can bejudged okay.It. is okoy,but only for the factory-ratedboost.Likelyitwilll08e3or 4psiot!lnysil,'TIificanUyin-creased airflow. That kind of loss is not acceptable. Thepurchase of an aftermarketturbocharger system is anideal occa.'lionto employ this book aljthe guide it is intended to be. An investi!fd,mid-mnge. or t.op---endtorque. The choic!' can easily encomp:u' two orthe:oostpressures /If luw efT" ocforl! ! urlJeis prod",:1'(/. The """,bers at Ihe all-eme right ore U,,,(",,.b,nerpm. Ag.3-8.TheTurbo-IIclia HJ compre5W" ",ill pllxlua 75() efm (l/ apreullre rotH)of 2.8. 1)IIllh'8 y,(>/d"fill of only 6O'-l. how the 8"rge 1m" lem'"/aIhe righI,illdj("ul"'!llilot theH-Jwill "Of W()rk alhIgh bowl prtMura d around a shaft to looklike a s nail. Unwrap this cone and clltolTLhc small end IIshort distance from the tip. The hole in the end of the cone I::;the discharge area. The area of this hole is the A of the N R ratio.Thesize of theholeissignificant,nsit determinesthevelocitywith which exhaust gases exit the turbi ne scrolland enter t he turbineblades.For any givenrate of flow,asmallerexitwi llrequirethat the gasesflowfaster. Thus, the area of the exi t is important in controlling the velocity of tile gases 8S theyenter the turbineblades.This velocityhasmuchto do withcontrolling the actual speed of the turbine.It is necessary to keep in mind that the area of this exit is the controlling factor in the bad sideeITect ofcxhaustgas back pres-sure and, thus, reversion into the t"Ombustioll chambers. The R of the NR ratio is the di stnnce fromthe center of the section area in t he cone to the center of the turbine s haft. All As divided by their res pective Rs will give the snme dividend: AIA2A 3A4A&A6 R)::n;'"113 ::R4=R6=R6 ::colis/alii Radius The R also has astrong influence incontl'olling turbine speed.[fone imag-ines that lhe turbine bladeUpswilltraveillboul asfalltas the gUllismoving FI, _3-12_To speed,which with of tht AiRratio,itis aimOfiIalways lilt diflChargt aroo Ihal !S chall gtd, wilh Iht radius remainill/l eonslalli. Splitlnlet ExhaustHousing SPLIT-INLETEXHAUSTHOUSING33 when it enters the t ip area, it iscnsy tosee thatll smaller R willimpm,t ahigher rotating spwd to the turbi ne. , +- ------1---.-. ... EXhaust ,.. It is of further valuetonotethat alarger R willefft..'(;tivcly give t he turbine shaft greater torque wi th which to drive the compres.'!Or wheel. The same force (exhaust gas) appliedwith agrenter lever arm (R)puts moretorque into the shall.. This, onoccasion, canallow n bigger compressor wheelif conditions SO require.Inpractice,however,itisalmost alwaysthe A that is chnnb"t.'CI,while the radius remains constunl. A simpli/ied approach to choosing the NR ratio is suouned up inFig. 3- 13, Sclcet ing what appears to ben logical stm-ling point fOI- an NR ratio is one t hing, but nct.ually getting t he right one isyet another. Trial and error is usual-ly necessary. A reasonable choice cun hcjudgcd by the numbers, or to some ex-tentbyperformancenndresponse.Judgingbythenumhf:rstequires measurementof exhaustmanifoldpressure,orturbineinletprl!ssure,and comparison with boost pressure. Theseat-of-the-plints feel oran improper NR selection is sluggi sh boost rise if the ratio is too large, The ratio can be so big as 10 keep the turbo from t.urning fuste!)oughtoproduce the deijircdboost.If the ratio ison the smull side,the turbo response can be so quick as to seem jumpy and difficult to drh'e smooth-ly_Itwillalso showup as fadingpower inthe upper third of the engine's rev range.Thefeelissimilar tothat of 11normally nspil-aied engine withavery small carburetor. "Choked' is arcnllOnable dcseription. A split -inlet exhaust housing permits the exhaust pulses to be grouped (or sep-arated)bycyl inder allthe waytotheturbine_Themerit of doingthis isin ktleping the individuulrmckage of energy, nnexhaust pull, intact tlndunmo-lested by olhet' putts all the waytothe turbine. This cnn gi\'e the turbine alil liebetterkickto get itmoving.WhenyouconsiderIh.IIbsolutebarrage or pulses and ent'rgycl)1l1inSt downth('tube fl"dtoII 75 76CHAPTER6:INTAKEMANIFOLD FIg.62.Top:tolNty!e intake nUlnifald with a sing"! throt/le Inlet. Bottom: Plelwm manifold wilhI/w/liple tI, rottle plates FlI.6-3.The big-block Chell),SuperRI/m manllaldlplcllllm/ throttle assembly. A compact deBIIl"wilh 8/101'1runners amI good illtcl 8 h a p e ~IhallL'Ql'k Wt'll al high {lowrote. Jf ;-r-oC: . I J.---.J street-'eof ruelout of the jet,producing a sudden rich condition. When t he gear cha nge is accomplis hed a nd t hrottle r e-applied, engine response deteri or ates, due to the sudden nir/fuel ratio change totherichcondition.The si tuationclearsupas soonasthe systemagain achieves a constantboost condition, where pressure is t he same onboth ends of the idle jet circuit. The bypass valve ill dcsib'1\ed to dump the pressure upstream of the throttle whenthethrottle is Qui ckly the systemto astabili:/:edpres-sure. Thevalve docs this byus ing the vacuum signal J,'Cncrtltedinthe inlake manifold when lhe throU.lc is closed to open a valvethat let s the pressure rap-idly bleed off'. Ven11ut>e I Resow boost PfetSU.c" plenum 1rmledia1e/y ahe. closing mro1Ue - -Fuel ,,, ssu.e - same as boos1

"- Pu.s_. - ... '--'hcuom due to (k sed livonia Vacuum signal VACUUMANGPRESSURI:GIITRIBUTION.Critic;)]to the successfuloperation of the blow-throughcarbsystemisthesourceof thesib'nulsusedtoCQn{,rolthe wastegate and fuelpressure regulutor. This condition ariscs fromabsolute Jla>d to control the pressure difference across the carburetor float needle. This pressure differenceisthe dilTerencebetweenthefuelpressufCpushing the fuelinto the floatbowl andthe boost pressure lhal exists in the floatbowl at FIg.8-11.Atypical rmtisurge value insta/-/atio" mmli"g fromJuSI a/l of lhe turbos onthe compressor discharge Nole the air filter ontheualue exit. LAYOUTOFABLOW- T HROUGHSYSTEM107 any given time.This pressure difference must be held constant under all oper-ationalconditions.To aceomplishthis,it is vitalt hat both control signalsbe taken fr om the intake pl enum prior to the t hrotUe plates. It is best to t ake the signals fromthe same location.To illustrate whutcanhuppenif thisrequire-ment is not met, imagine hooking both signals to the intake manifold after t he throttle plate.Thi sisalways the last place to see boost pressure, and it isal-ways the lowest pressure. Pressure losses thru the curb can be as high as 3 or 4 psi.If the wastegat c sibtnalthen comes fromthemanifold,the floatbowl will see apressure 3 or 4psi greater.If fuel pressure is J;ct5 psi above boost pres-sure, then the real pressure difference across the float needle will be 1 or 2, cel"-tainly not enough to run under boost.If fuel pressure is raised to compensate, the idle setting will be ofT when I,he fioat bowl sees atmospheric pressure. Back at idle, fuel pressure willhe 8 or 9 psi, an unstable fuel pressure for 11float nee-dle assembly. PREPARINGTHECARBURETOR.Several aspects of the carburetOI' need inspection and/or preparationfor use in a blow-through application. The blow-through curb must have a solid float. Should the one you choose to usc have a brass-sheet float or other style that could collapse under boost pres-sure, the float must be replaced with a soEd unit. A variety of techniques exist to fillahollow float withlightweight fomn.Some of these come in aliquid and harden after being injected into the flOat.Consult the Yellow Pages, under ad-hesives. Inspect the carb forlead plugsthat cap ofT intersecting drilled passages. These plugs are prone to dislodge with boost pressure. The plug can beretainedbystaki ng it inwithasharp-pointed center punch. Set aring of punches aroundthe plug suchthat the base metalof the carb bodyisraised enough to create interference should the plug try tomove.Another method of retaining the plUb'Sis simply to cover them with ahigh-quality epoxy glue.Be mindfulof the fuetthat largerplugswillfailfirst,as they inherently have a larger force trying to push them out. 108 CHAPTER8:CARBURETION FIg.8-12.Signals {or the was/egale and {uel pressure regulator need to ongi,wte ai/he same {Xlint illt he system and b{ore the throtlle plale. Fig.8-.:13.When("ei leakage allhe Ihl"Otile shafl i8 a problem, boost press,, !'e {rom aboue the !Jenillri.which will always be greola IlilllP ehalbelow the vell/llri. canbe,honneled 10the shurt pivot bores /0 blow t he mixture back into the throat. _, Plenum Pressure signal To carburetor , Pressure s19nal

Rlllum Inspect all the gaskets in the carburetor. Any gasket that appears less than up tothetask must be improved. It ispossible to retain agasketwithavery lightcoatingofLoctiteappliedtoonesideonly.Undernocircumstances should youuse asilicone or similar rubbery-style sealer, as you will befinding it in the fucljets after the fi rst trip around the block.Itis especiaHy important to seal all gaskets or other items on the float bowl lid to avoid losing boost-pres-sure balance across the mainjets. If any pressure leaks whatsoever occur fmm the float bowl . fucl dclivery wil l grow lean onrising boost pressure. Thethrottleshaftsont hecarbwillseepfuelunderboost.if notscal ed against pressure. Most soopage willbeint he annoying category andwillnot afTect safety or function. Cosmetics dictate that the shafts receive some form of seal.Probably the easiest and most efTective method is to olTer a pressure bal'-rier that willtend to fo rcethe air/fuelmixt ure back into the carb throa t.This can easilybe done by bleeding some boost out orthe plenum on the face of the carb, downto smallfittings placed into the bosses through whichthe throttle shafts pass. '-1/

:'" 0 ./ Fual vapor i driven inwar , , Cold-start valves of the fuel-dump style, rather than the air-restrictor type, may need to be pressure balanl'ed against a reverse flow when operating under boost. Should this bea problem,it can be dealt withby creating acap of sorts over the cold-start valve and bleeding pressure fromthc plenum into this cap. The cup can be bonded onto the carb with a high-quality epoxy cement. Cold ..tarf oo/ue$ ron Of)mmQlliy leak badwc"d fwdl!r bilOlil , A pressure bal-ance acfUf;J; the valIN!' will solve Ihll problem_ LAYOUTOFABLOW- T HROUGHSYSTEM109 Cap bonded to YlIMl S UITA.l l!CAIt fOItBLOW- THItOUIi HAPPli CATION_Almost any carburetor canbe preparedforusein(lblow-throughturbo system.It isclear,however,that some carbs present a serious preparation chall enge, while othel"8 are just plai n easytouse.Manufacturers likeWeber, Mikuni,SK,Dellorto,andHolley all makecarbsthatwill,wi thsuit!lblepreparation,runctionwellinablow. throughappli cation.Theeasiestunittouseiscrortll inlytheMikuni series PHH dualthroat sidedrafi..Its houldbegivenconsiderationinapplications rangi ng frOIllVoSsandY-l2sto!lnyinl ineconfiguration.The MikuniPHH comes as close to usable right out of the boxas is available. It is simple to tune, responsive at low speeds, flows huge amounls of air, and islong-t.erm durable. The new SK carb is virtually ilS equal, with perhaps even greater fine-tuning capability.In situations where itisnot possible touse dual -throat sidedrafts. the Weber JOF downdrafts ought to be given considerat ion. Although the lDI" requiresextensivepreparation,it is abroud-range,responsive, smooth- run-ni ngcnrb. Perhaps the highest-quality carb built in the world today is the It.al-ilm Dellol'lo series. Availnble in downdl-aft and sidedraft (:onfigu rutions, these cur bsare truly finepi ccl.'!)of work. Prior to !letting you rheart onusi ng them, secure yourpathforparls supply_Holleycurbshavebeenusedsuccessrully over the yean;, andHolley ofTel"8awidevari ety of sizes and shapes_ No manu fncttll"er t"Omes close toHolley in oITering special-tuningand pieces to tai -lor aspecific application. Motorcraft two-bnrrel carbul'etors are versatile and easily adapted to blow- through configuration. PLENUMDESIGN_The plenumist hecomponent focusesair foritslrip through the carboAlthough plenullls are simpleinconcept.afewrules should be observed in plenum design: Makethe volumeof the plenu m110-120% of the engine displacement. Straightenouttheai rflowbeforetheairCQrr ectorjetassemblies.Air swirling 11round an air l."OITcctorprtlventsthe jet fl'omfunctioning. Have the shape into the curb throats approach that of an ideal inlet. Don't blowair directly across acarb throat. Provi defor air bleeds to the floatbowl s. 110CHAPTER8:CAR8URETION FlC.8--:15.The ple""m llent ports to the throllie boresmUSIinOOl1)()rale abcllmo"lhed form oppf"O{J(;hing an ideal air inlet shape. / , / AN DFURTHERMORE . DoelSan air/fwd mixtllre have trouble staying atomized through an idling turbo allow ambient temperatures? Draw.through-carb turbo s y s t e m ~inherently have a lang, devious route for the air/fuelmixture to travelbefore reaching the cylinders.If heat isnotpro-vided ut the carb mount or [Jeurthe system's lowpoint, fuelwillpuddle inthe bottom orthe turbo. In prnctiee, carb preheat allows the engine to idle and run smoothlyat lowspeedswhenambienttempcrutureislessthan80F.Under boost,suchacyclone existsthat puddling isimpossible.The problemcanbe avoided completely by blowing through the carbo Are blow-through carb systems techniea.1.ly Gild functionally workable ? Yes.For some heavy-hitting evidence, drive aLotus Turbo Esprit or a Mase-rati Bi -Tnrbo. Hasthecontroversyof blow-throughve,.susdraw-throughcarbsystems been.resolved? Not onlyyes,but hellyes.mow-throughstarl..sbeller,idleshetter,runs smootheratlowspeed,andproducesquickerthrottleresponseandlower emissions.AnintercoolercallDillybeusedwithablow-through application. The draw-through system is a deadfish. Voltage SparkPlug5 Flg.9-i.Tht:di!fcrcna belWII" oo/dplugond a Itol "lug is Iheease ( ~ i t l (whichhwt i, fmn'ferreti Olltof the Cl!lIter electrode. EVENTSINTHECHAMBER Therealtest of at urbo engine lindits abil ityto produce huge amounts of power(withoutleavingat rai lof pungentblue-graysmokeand/oralumi num/iron shrapnel) boils down towhat's happening int he combustion cham ber,Spar ki ngoff acont rolledtemperatureInixture--composedof t heright stuff at the right time-ist he culmination of all the desi gn effort put into the system. When this event transpires correctly,the fun begins. Igniting the ai r/fuel mixture in ahighpressu.re turbocharged engine is tough. The crux of the matter is t hat air is an elect rical insulator. The more air mol e, cules packed into the combustion chamber, t he greater the voltage required to (hive t he spar k across the spark plug electrodes. Large amounts of voltage arc required at high charge densities.Not only are high voltages required, but all items that carry t he high voltage must be insulated withmaterials ofhlgh di electric strength. This willinsure that the voltage really does drive t he spark across the plug gap in!ltead of to the val ve cover.Thetolerance for deteriorn tion in t hese components is small, again due to the high voltages. Mostignition systems olTeredliSOEMinthe late eighties have sufficient voltage to fire ofT the mixture at modest boostpressu res of 6 to 8 psi.Greatet boost pressures will likely requite a capacitor discharge ignition supplement to supply l.'Onsistent igni tion. In any system where spark plug lifebecomes intol erably short, a cupncitor dis&harge unit willbe necessary, 'rhe choice of a spark plug for u turbo engine application is relatively easy.The heatrange of the plug is the keyfactor to get right. Classifying plugs by their heat range has nothing to do with when or how they manage to g e ~t he fire go ing. "Heat range" means no more or less than how the features of the plug al'e ~ rT'" Hoiplug U1 112CHAPTER9:EVENTSINTHECHAMBER I gni tionTimi ng Fig.9-2.The direct [ire,ignition system {rom t.'/ectromatiueit!ideal {arctls/omiCnili01l c"rlJt's required {or tu.rbocharged configuredtoawayfromthe electrode.PI'esumefOI'amoment that it is desirable to have t hematerials of all spark plugs operate at about the same temperature, regardless ofload conditions imposed by the engine. Then the spark plug of a low-speed, low-load, low-compression engine would need to conduct hoot away fromits electrode slowly, or else the plug would operate too cool. This is called a hot plug. An engine of our liking, clearly, must have plugs that conduct lots of heat awayfromthe electrode. This plug, then,willbe re-ferred to as acoldplug. The balanceto achieve isto keep the plug hot enough to continuously burn the soot and deposits off yet coolenough to keep the ma-terialsfromrapiddeterioration.Aplugthat operates at toohigh atempera ture can also serve as an ignition source that actually starts the fire prior to the spark. This is pre-ignition, and it can lead to detonation. In the actual selection of aplug for a high-pressure turbo engine, the choice should start with a plug about two ranges colder than stock equipment. If the plugdeterior atesrapidlyorfracturesinanyway,Lryathirdrangecolder. Should the plug get dirty and acquire too much to fire,back up one range hotter. Installation technique will contribute to the plugs' consistency and durabil-ity. Certainly all threads and washerseats must be t horoughly cleaned. A prop-er spark plug lube, like Never-Seize or molysulflde, should be lightly applied to the threads and between the washer and plug. Top this olTwith tightening the plug tothemanufacturer's suggested torque, and youwillhave done all you can toward good spark plug performance. Torque specs are usually between 10 and14f\.-lbfor aluminum heads and 16 to 18for iron. Tgnitingthe mixture at the right time is also a challenge. The turbo engine adds one more requirement tothe design of an ignition curve. Turbulent turbo mix.-turcs burn faster than normally aspiratedmixtures, but the denser mixtures slow the bum. While contrary and confusing, this generally lenves the situation not nel.>ding to begin the burn quite sosoon. The igni tion curve cant herefore benefitfromasmallretardfunctionasboost risesandthemixturebecomes both densel' and more turbu lent. The correct ignition timing under all circum-stances is achievable only if the timing curve can be designedright along with thefuel curve. With today's technology,this can be accomplished only withaf-tennarketenginemanagementsystems.Atpresent,theElectromotiveand DFI engine management systems can contl'ol both ignition Imd fuel curves. Electroni c IgnitionRet.rd Fig.9-3.Tht ad;ullt-able boo$/pre/lslut-odul.l1ed ignitio" rdard {rom MSO. KnockSe nsor ELECTRONICIGNlTIONRETARD113 The boost-pressure-sensitiveignition retard olTers alimiled degree of adjust ability to the igni tionsystem operll (ing under boost. This i\.emenn also prove usefulinpermitting greater ignitionadvance at low speed and cruise condi tions while reduci nglop-end advance at high boost pressure. The ignition re-tard can easi ly bcjudgedjust a safety device, but it's not quite so. It alsoallows aroughtail ori ng of thehigh end of the ignition curve to the octane rating of the fuel.A si ngular dit:wdvantage exists withthe pressure-activatedretard: it willprogressivelyretard ignition liSboost rises, evenwithout thepresence of detonation. Therefore, timing is less than optimum at these midrange points, so that it will be right at maximum b o o ~ t . .This trunslates to n noticeable loss of mid range torque. Lesstorque + less power= less fun. The pressure-sensitive ignitionretard could be called a passive device, in that it does not detect the presence of the event it is ther e to prevent.It retards the ignition based on boost and retard rate setting only.The knock-sensor ignition retard s hould be calledlinuctive device, however,becauseit detects thepte!;-ence of the eventand then is charged with the job of eliminating it. The knock sensor does an excelle nt job of retarding ib'llition when detonation is detectM. This implies t h u ~m'lXimum safe power is being developed under the operating condi t ions at that instant. Forexample,addoctnne,andignitiontiming staysfon... nrdwhilepowel' slays up. The knock sensor is an override safety device thut isnot the least bil concerned with maximum power.lfused in an absolutely correct environment, the knock sensorwould remain quietly in the background and never be need-ed. Never, that is, until somethingwenl wrong, wrong, wrong. A knock-sensor-controlled ignilion curve cun di splay a less-than-fun churacteristic. A check on the functioning of the system, as frequently st...... ted in service manuals, is to rap onthe cylinder blockwith IIhammer.If the sensor detects the knockand re-tards the t iming, a udibly slowing the engine, it. is working as designed. Clearly, hammering 011the !lideof theblockisnot detonation. Why,then, shouldthe retard be activuled't Is it possible that al'OCkbouncing olT the block could also retard t he timi ng? How about afailing hydraulic liner, a waler pump bearing. or abrokenaltel'llator mount?It isllCCCssaryto keepinmindthat relarding lhe ignition raises exhaust gas temperature. This is decidedly a bad thingto do_ unless detonationreally is present. It is probablY !ltretl'hing the point a bit td 114CHAPTER9:EVENTSINTHECHAMBER Rg.9-4.AllOc/'W kllod.d.. lf!Ctum .ylll.. m w.th control 0/ '8,utu;m t.ming i.sanmron. of talob/Ishing a of MJfelyfor anMs",e. Thellll,tenl.B often add. powtr 08 lIIell os safety, by pemuuing igllitiol!timillg 10slay closer/0 flu! knock threshold Iholl's poui-ble whellII/nmg by eor. Fuels suggest that afast trip downalong gravel roadmight retard ib'l1itiontothe point of melting an engine. Mechanical noise of 11high-revving engine can cause sonle knock sensors to activatewhennoknockispresent.Thisthenbecomesarev-basedretard, which is not 11desirable device. The development of aknock sensor into afull.f1edgedcomputerthat docs whatits softwaretellsit todoisthemostoptimist icdevelopment yet seen. These are intheir infancy,but much progress is being made by J&S Elect ron-ics.Programming will , woul dn' t you know,be the key.Perceived downsides of the knock sensor are not always present.It is,however, necessary to consider these possibilities uponpurchase, adjustment, and use of a knock sensor. Much can be said about the pluses of aknock sensor. 'I' he cont ribution it can IIl1.1ketowardpeace of mindisnot without merit.The vastml\iority of turbo system im;;tallations arc not maximum-effort systems;therefore, smallpower compromises are not crucial. Therein probably liet! t he of the knock sensor's value inthe scheme of th ings.Overall, the knock sensorisprobably the best t hing goi ng for of ignition Wming. The quality of the fueloffered up lo the burning process is keylo the function-ing of powerfulturbo engines. Highoctane,qunlityrefinement, and fastburn rate are the di stinb'tlishing characteristics of b'OOdturbo fuel.Anoc-tane raiing is solely u measure of r esistance to detonption as test(.'(lin a tub iest enbrine.QualityrefInement istheproductionof gasolineswithout unwanted contaminants, often referred to as "abad tank of gas." 'I'lw combustion rale is just the relative rate at which the fuel burns. Combuijt ion rate has a significant effect on detonation characteristics of the fueland chamber.If the burn rate can be significantly sped up, the little pockets of mixture hidden orr inthe ex-tremes of thechumber won't have time to overheat and explode. FIg.9-5.Proper gouging tellshow

{lme/laning.These combi,,(ltia" gel uses package nicely ond offer nweollh of infortnoliml. FUELS115 Absolutelywonderfulchanb"l..'Stake placeas detouationispus ht>dfurther out of the picture.A hydrocarbon culledtoluene presents turbocharging with un intriguing new scope. Toluene is a distillate of oilcommonlyculled methyl benzene.ItillaOOU5inof gasoline. Of some interest isthefactthat itisthe third component of TNT.That should not imply its power; it isjust a curiosi ty. It docs hove the remarkable ability to spt.oedup burn rate to such on extent that boost pressures defying imaginat ion can be used. Tol uene was the fubledFor-mulaIcarof t hemid-eighties. hundredhorsepower from90 cidat 75+psiboostindeedrequired somethi ng out ofthe ordinary. Think aboutthat for amomentinsomehumorouscircumstances.AMazda Miata with 1450 bhp comes quickly to mind. Or a NASCAR Winston Cup stock car racer with 5800 bhp. Aninteresti ng means of having fun, indeed.Presum-ably evenRichardPetty ut hisbestwouldhave found thot a choJlenge.Inthe practical use of stroot fuel,octane rating becomes the most important aspect. In general, throo octane points will offer about 2 psiofboost-llSSuming, of course that al l other factors remain in line.Refonnuillted gasolines, which in-clude alcohol, nre not generally suit.o.ble for use with turbos.Octane improvers arcreadilyavailabl eandshouldbeconsideredaviablemeans ofpermit ti ng greater boost- pressure levels. Additive quantities vary with brands, so follow-ing eachmanufacturer's reic at first thought, but consider how fast heat would be drawn out ofa high-conductivity, infinitely thick aluminum manifold, as op-posed to a very thin piece of stainless surrounded with anice ins ulator like air, Heat tr ansfer is directly proportional to surface arell.It is therefol'e reasonable to give considerable thought to keeping the exposed surface area of the exhaust ll1!lnifoldto an absoluteminimum. Clearly,the less surf!lCCarM,the less heat loss.Reducing the amount of ambient air flowing around the exhaust manifold and turbocharger willfurther reduce heal loss fromthe system.Il is generally not feasible to directlywrap the exhaust manifold with aninsulating material, as the manifold material it.sclfwill overheat to the point of structural failure. A further effect on heat transfer out of the exhaust manifol d is heat distribu-tioninside the manifold.Hot spots inside the mani rold shouldbeavoided, be-causethey canquicklypumpalotof heat out. They al"Ccreatedbys harply angled intersections or by too muny exhaust pulses through one segment orthe manifold, Keep in mind that the temperature difference between the inside and outside of the manifold is the force that pushes heat through the manifold, Reversalof the exhaust gasflowbuckintothe combustionchamber during valve overlap is calledrCYClsion. Creating an aerodynamic barrier that roouc-esthet'everseflowyet doesnotimpedeoutward-flowing gaseselinpaydivi-dends in performance. In general, much greater freedom exists in the choice of manifold styles when the manifold is fabricated, These choices range fromthe simple log s tyle to the 12.CHAPTER10:EXHAUSTM AN I FOLDDESIGN Rg . .:10-3.Durobi/ilyo( WIexha"st manifold con be influ.enced try the oosicdesign. A log-style manifold is subjed /Q more hew abu.seand thermal expansion than a separate-tube header. Overlapping heal pulses;II the log style creole e:drahoi spots G"d greaterAg ..104.The anti reversion crme can offer G reductiOl1in exha",,1 gm;reversioll during ualve ouer/ap.The cone creates aparliai barrie'-to reversal of flow. Hot - high-expansionCooler -low-expansion manifold '" , , equallength,multiple-tube,individual-runner style.A greatamount ofI"e searchhas been done on t heperformance benefits of various manifold styles. Most of thisresearch, pl\!sthetremendouse!Tortsput into the reeent era of turbocharged Grand Prix cars, strongly indicates t hat the best manifolding is multiple-tube, individual -runner style. TUBI,.GSIZES.Almost allapplicationsof aturbo are toanexisting engine. Therefore, the choice of t ube sizes willusually be dictated by pot-l size and the size of the t urbine inlet on the turbocharger. Where a clear-cut choice does not exist,it is best to select the smaller of the sizes availabl e,thus increasing ex- gas vlliocity. U RULE:When achoice exists as to tube size, always opt forthe smaller, to keep gas velocities high. Fig .1.0-5.Four-in/o-onl:designs for4" or 8-eylinder ellg;IIes Fig .1.0-6.An CIample ofgood.compact manifolds. These desigll s also use weld tis. Fig . .1.0-7.V.12 cilstom "earle':The sharp in/ersection.sareriot idealfor power.wng col/ector tubes are going toexperience large thcmwl expcUlsion. 1lf!Cf!ssilu/ilig flexible braces 0" the ("rbos. STYLEOFMANIFOLDING 121 122CHAPTER10:EXHAUSTMANIFOLDDES IGN Fig,:to-B.Jim Feul Illg'S wild IwillAuriJe Quad 4featured SOme 0{ the bestheader" ewr built.Note the particu-larly smooth roUectorll. Fig.:to-9.Aweld el IIw/lifold.Nole cuts in the flaugetoauoid warpage 011thermal {'XIXl l!SIOIl. The strength of the manifold willbe controlled largely by the wall thickness of the materials. In a fabricated manifold where wall thickness drops below .09 inch, it may benecessaryto support the turbo by a brace or small truss assem-bly. The thermal expansion of the manjfold willtend to move the turbo around as the heat cycles up and down. Thus, amount must have some degree offlex ibility whilethe weight of the turbo. Mandrel-benttubes are avail-able inawide variety of sizes to meet theneeds of the customheader maker. These are generally high-quality items and cun be fabricated into allYbundle-of-snakes style turbo manifold one's imagination can conjure up. Avariationof the tubemanifoldcan beconstructedbasedonacast-steel part calledaweldel.Weldelsare basicallyindustrialhydraulicequipment, used commonly in oilwell and other similar heavy duty applications. These els are available in a variety of sizes and radii, and in either mild steel or stainless. Althoughheavyandexpensive,weldelscanbe usedto formaproperhigh-strength manifold. Wel d els are sized aC{."Qrding to pipe nomenclature-that is, inside diameters. FIg .1()..10.We/({ e/ mamfolds as a f .. n(fiollaJwork O{"" FJ8..1o-U.Fillittg weld tis together fa formIhetriplelurbo Jaguar exfwusl manifolds Tabl.10-:1..m ~ l dtl.re-lrelwn chart for 90" et. OOW$(i",;hes) NominalBend pipe 8i:z;eradi us 1/2 1>/2 3/,1 1/8 111/2 1l/41 7/8 1112 2 U, 23 21/2;;I3/a\.e vent tube or tailpipe willsuffer unusually large fluctuations in operating temperature. This situation exists because the wastegat.e is closed most of the time, and the vent tube willthus be cold, since no exhaust flowis r 1----dwastegate valve willseldomkeepthe t urbo from producing about the Ilormal amount of boost, but it will take II.lot more revs to reachthat normalamount.If, fo r example, t he Wast.cWIt.c valveseizes at the positionitreachestocontrolmaximumboost,thesystemmustproduce enough revs just to overcome the leak before produci ng any boost. 'AII.I'II'IE.Any failureinthe tailpipe that creates ablockageforthe exhaust gaseswilltendtoprodw:;eahigherboostthresholdand/orle5Smaximum boost.Checkthepressure inthepipeupstream of anypossibleblockage.In general, back preS!!ore greater than 10 psi will cause almost a complete loss of boost.Back pressure greater thon 2 psi is undesirable under any circumstanc-es, even if not of a magnitude to cause loss of absolute boost pressure. AIRfillER_Anair filterthat istoosmallortoodil1.ywillkeepthe sYl'tem fromfunctioning uptoexpectations.This conditionwillalso create thebad side-effect of raising intake temperature. COMI'ItIESSOllINLETltO.fI.Al most always, the air falter or airflow meter will be connected to the turbo compressor inlet by flexible hose of some sort. If the fil -ter or flowmeter is restrictive, it i5possible for the vacuum thus created to col -lapsetheconnectinghoses.Usuallythesymptomof collap!:linghosesisa sudden loss of allboost. The force!!onlarge hoses fromsmallpressure differ-ences can be deceptively large. MIIiFIRIES.Anymisfire while under boost willb{)cau!i(.'Iiby afailure to ignite the mixture or byanair/fuelmixturetooleantoburn.Failuretoignitethe mixture can be a bad plug, wire, coil, or all those stock ignition problems. !fthe ignition checks out proptlrly, thenthe problem will be foundwiththe air/fuel ratio. BOOGI NG.A di stincttypeof full-throttlemalfunctionisOiloverlyrichairl fuel-ratio-inducedbog. This is manifested in aloss of power at fullthrottle, of-ten accompanied by black smoke from the tailpipe. Another frequent cause ofboggillg, with similar full -throttle feel , is an over-active ignition retard. A failing knock sensor can indut-e the Slime symptoms. A dangerous sideefft'Ct of retarded ignition is a dramatic ri se in exhaust gas t em-perature.Exhaustmanifoldand/orturbine damage canresultfrumretarded timing. DETONATION.The audiblemetallic pinging sound of detonationi!!a clem sig-nal that the engine's life is threatened. Every effortmust be focu8(.'Ii on ridding asys tem of detonationprobl ems.The widevari ety of detonationcauses can prove lengthy to troubleshoot, but a turbo engine that pings under boost must be considered apcndillg seriousexpense_In generol , all detonatiunproblems willstemfromoneof t he sixiterm;discussedinthefollowingparagraphs. Their likelihood as the source of the problem is approxi mately the same as the order in which they arc listed. Octalle.A fuel'8octaneraLing is IImeasure of iUlre8i stanco to spontaneous combusLion, or detonation. The greater the octane, the brt"tlSicplumbh.g (1'f!I1I Porsche, 1M one would &/1/.The intercooler wn gel tlXCf':luml umbie'"air (rom IHIhi"d the rOOr""d i, protected by II hW)' Flg.iT-5.Thegrt(ll. Turbo GTO ud one walitegate 10 C'QnlroilwoNOle Iht it,lq:ratlOn of 1111/" 8urge vailit's,nto both rotnpres8(Jrou/leI8, The intercoolers show g(J()() mlermJI sl1"/.'amlilllllg and generous core area. tmt ambie,,' cooJIIl8 air 18'IX'ru. Can the tubes be routed conveniently to and fromthe intercooler, (l nd do they meet flowrequirements? Willthe coresreecivc IIdet pressure. TESTING229 Several objectives must be met in the testing prol:edure: Ascertain fuelpressnre rise rate as afunction of boost pressure. The needle valve is the fuel pressure adj ustment. Adjust in one-twentieth-turn increme nts until the desired fuelpressure is achieved according to the following table: Boost pr eSliu re (psi ) o 2 4 8 Fuel preSll Uf e(psi) 35-39 47---53 60- 70 95-100 Determine that no combustionroughness or engineknockoccurswhen operati ng at maximumboost. Boost pressure should bebetween 4 and 6 psi at fullthroLtieat 2000 rpm. If less than this,cal1the manufacture rforconsultation. Maximum boost pressure should be 7to 8psi CAlIlION-DuetoIhesparseSOUlldInsulilliononIheMiara,knockisdifficult10 Ilesr.Pay careful allen/ionto{he sound of del on arion.as ilisvery dam-aging/0me engine. If knock is detected, lill off the thr()ttle immediately. Drive t he car a few miles prior La applying boost.If a llsystems are operating normal1y,proceedwiththetesling_General1y,usethirdorfou rthgears,to koop events at aslowerpace.Apply boostinsmall increments, sothut no sud den changes occur. Circumstances can combine lo make the Aerochru'ger either less or more re-sponsivethan desired.If eit her caseisperceivedduring tesWng,cuUlhe kit manufacturer forfurther guidance. Whenthe engineruns smoothlyto the redlilleinfourthgear at 7to8psi boostpressure,with ct:n-red fuelpressure andno hint of detonation orrough combustion. the instalbtion may be considered compl ete. 230CHAPTER18:INSTALLINGATURBOKIT FIg.1.8-27.Wi. eu/est "'IJ (lnd tu>ri.ng(lI1! done.rt.mOI.:ethe rllfd prt.uurt. gauge.TM ills/al/alio" may be ooiliuJered comll/ele. GeneralRul e. ofOperation Remove the fuelpreasure check b'Il uge. CAUTION-Fuelspillagemay occur. Review the insW'uctions and installation for any detai ls overlooked, and cor rect as requi red. Use 92+fuelat 1I111imes. Higher,if available. Donot applyInaximumboost for more than15-second durations. Ifanysoundsof roughcombustionoccur,ceaseusingboostuntilthe cause isidentified and (:orrected. The oilmust bcchecked every 10,000 miles in the turbo reservoir. Donot overlill.Oilrefillint.crval willbe 20,000miles. MobilOilsyntheticSHC630istheonlyaceeptableoilfort heAero charger.ThisisavailablefromthekitmanufactureroraMobilOil products distributor. Useextreme caution whendriving thevehicle onwetpavement, asthe rate of boostrise can cause an unCJ(pcctedloss of tl'llction. The foregoing procedure is typical of the installation of an anermarket tur bocharger system.There are manyreasons torespect the process. Thel-care none to fellf it. SUPPLIERS Advanced Engi neering 310-327-9336 EFt systems,injectors, Fuelpressure reguiliton, Fuel pumps, Fuelsystem items. Throttle bodies AI!;Miller 310-949-2858 Turboch1lrg(!l'1l. Wastegat.e!l Alamo MotorllpOl'ls 2106370373 Boollt controllers, Puel prC$$ureregulators, fuel system items, lnterroolers, Surge valves Allied Indust ries 909-279-5712 flanges, GaskeL&,U-bends Applied Te. jella, CoIf, CTISer.ieeManu.l: 1985-1992 C.soli ".,.nd T"rbo including]6V lkllt!ry P"(,I,,I,m ISBN0-l)37M'1342..(l Super Beellc,Beetle andK ..",.nn Chi . Offici.1 Service Manua l:TypeI, 1970-1979 of AIII(rirn ISBNAUTOMOTIVEBOOKS AND MANUALS il