Report by the Committee on Motor Vehicle Emissions (1973)

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3. POTENTIAL OF SPARK-IGNITION INTERNAL-COMBUSTION ENGINES PASS ING EMISS ION CERTIFICATION FOR 1975 and 1976 3.1 Introduc t ion The invest igat ions of the Commi t tee to date have shown that , accord ing to current planning of the automob ile manufac turers , the great majority of the engines to be used in 1975 -76 model year vehi­ cles wil l be conventional , reciprocat ing , spark-ignit ion engines . A smal ler fraction o f the 1975 -76 vehicles wi l l use Wankel rotary engines , and one manufacturer (Honda) has plans to produc e a new type o f carbu­ reted s tratified -charge engine . S ome pas senger-car diesel engines wi ll s t i l l be produced , but these wil l di ffer only s light ly from the dies el engines currently availab l e . Dies e l engines are discus s ed more fully in Section 6. 1. This section of the report wi l l pres ent an analysis and evalua­ t ion o f the prospects o f spark- igni tion engines pas sing the emis s ions certi ficat ion tes t for 1975 and 1976 mode l year vehic les . 3 .2 Current Status o f 1975 Systems The January 1, 197 2, report o f the CMVE dealt at cons iderab l e l ength with the techno logical feasib i l i ty o f meeting the 1975 standard s . At the present t ime , mo s t automob i le manufac turers have developed s ome­ what simi lar prototype emis s ion-control systems for their 1975 model year vehic les . The major U . S . and foreign manufacturers are current ly as sembling and testing f l eets of vehic les equipped wi th the comp lete sys tem to evaluate different promis ing catalyst materials and to obtain data on system durab i lity before final production des igns are frozen . These 1975 emi ssion-contfol sys tems typica lly consi s t o f : (i) An improved carburetor to provide more accurate fuel metering , wi th compensation for air -dens ity changes , and with an - 22 - Digitized byGoogle 

elec trical ly powered choke that comes off quickly at ambient t emperatures 0 of about 7 0 F . (ii) A quick-heat intake manifold designed to promote rapid fuel evaporat ion after engine s tart-up . (iii) An e lectronic ignit ion system to eltminate the wear and o ther problems o f current distributor as sembl ies and to allow easier spark-t iming control . (Inadequate maintenance o f pres ent dis tributors commonly results in increased engine emis s ions . ) ( iv) An exhaus t-gas recyc le (EGR) line and contro l valve de­ signed to recyc le about 10 percent of the exhaus t flow to hold NO X emis s ions be low 3 grams per mile (g/mi le) . (v) An air pump to inj ect air into the exhaust ports to oxidize carbon monoxide and hydrocarbons . (vi) A catalytic converter in the exhaust sys tem to promote further oxidation of the HC and CO emis s ions from the engine . For some manufacturers , the current fleet tes ts represent the firs t extensive evaluation of the comp lete engine emis sion controls with the bes t oxidation catalyst materials now avai lab l e . Data ob ­ tained from some o f these manufacturers ' fleets are shown in Tab le 3 - 1. �oa t of the data in Section 3 o f this report were received in reply to a quest ionnaire dated July 13, 1972 or were presented during recent panel visits . ) These tes ts fo llow the durab ility driving cyc le and maintenance procedures used in the emis s ions certi fication of vehic les . Progress in emi s s ion control for 1975 syst ems us ing catalyt ic converters has been made s ince the CMVE report of January 1 , 1972 . I t is highly probable that most manufacturers wi l l be ab le to produce vehicles that wi l l pas s the 1975 certi fication test procedure , provid ing - 23 - Digitized byGoogle 

Emi s s ions Per formance o f Ma jor Manufac ture r s 1 9 75 Mode l Year Deve lopment Flee t s a Emi s s ions i n gmslmi le Vehicle We ight E ng ine S i ze No . of Ma nufa c turer Range , lbs . Range , C ID Veh i c l e s Mile age HC - co - NO --x 4000 - 5 000 b Ford 25 0 - 460 8 4000 0 . 46 3. 2 2.7 7 36000 0 . 73 5.2 2. 2 e Ford 4000 - 5 000 25 0 - 460 6 4000 0 . 34 3. 3 2. 2 5 36000 0 . 40 2.6 2.4 b Genera l Mo t or s 2750 - 5500 140 - 5 5 0 30 4000 0 . 34 2. 3 2.0 17 1 2000 0 . 42 2.6 2.0 7 24000 0 . 39 2. 2 1.8 N b � Ni s s an 2 75 0 98 5 4000 0 . 29 1.8 1.0 5 16000 0.50 2. 2 0 . 95 1 245 00 0 . 48 3. 8 0 . 95 d Toyo ta 25 00 97 6 4000 0 . 35 2.9 1.4 4 12000 0.52 5.5 2. 1 3 24000 0 . 66 9.0 1.2 � 0 a - 19 75 CVS -CH t e s t procedure . Durab i l i ty d r iv ing s chedule , ma intena nce , and fue l u s e d approxima te tho s e ant i c i pated i n 19 75 cer t i ficat ion pro cedure . <6" ;::+ Emi s s i ons averaged over a l l veh i c l e s t e s ted a t tha t mi leage . N. CD No c a t a l y s t r e p l a cement s were ma d e dur ing any o f the s e t e s t s . Q. rr '< b - Emi s s ion control sys tem : engine mod i fi c a t ions , a ir pump , oxid a t i on c a t a ly s t , E GR . C) c - Emi s s ion control s y s tem : eng ine mod i f ica t ions , a ir pump , 2 oxid a t ion c a t a lys t s ; EGR . 0 d - Emi s s ion contro l sys tem : eng ine mod i fi c a t ions , mani fo l d r e a c tor , a ir pump , ox id a t i on c a t a ly s t , EGR . & ,...._ (\) 

a l lowanc e i s made for one catalys t replacement during the 5 0 , 000-mi le durab i l i ty t es t s , that fuel containing s u f fi c i ent ly low l eve l s o f l ead and o ther cataly s t poisons is u s ed , and that averaging o f emi s s ions wi thin automob i l e and engine c las s es is a l l owed . Emi s s ion-control sys tems are al s o being deve l oped that do not use cataly s t s and therefore have improved durab i l i ty over the catalyt ic sys tems . The three-valve s trati fied-charge carburet ed engine, under development by Hond a , has achieved emi s s ions below the 1 975 s tandard s at low mi leage on compac t cars ( for d e tai l s, s ee S e c t ion 3 . 9 .2 ) . Three vehic les e quipped with a 2 - l i t er engine ( 122 CID ) have comp l eted 5 0 , 000- mi le durab i l i ty tes t ing and met the s tandard s at every t e s t throughou t the t e s t period . The Wankel engine w i th a thermal reac tor has achieved emi s s ion leve l s below the 1 975 s tandard s in a compac t c ar . This sys t em has a lready d emonstrated improved durab i l i ty over a catalytic sys t em . Data from the few c ars t e s t ed over extended mi leage ind i c at e that d e teriora­ tion wi l l be re lative ly low . 3.3 Engine Emis s ions for 1976 Sys tems 3.3 . 1 Introduct ion In deve loping sys tems to meet the 1 975 s t andard s , mos t automo ­ b i l e manu fac turers have emphas i zed that s uch systems mus t b e compat ible wi th 1 9 7 6 requirement s . There has thus been a concentrat ion on 1975 control sys tems that can b e mod i f i ed to ach i eve the greater NO emis s i on X contro l cal led for in 1976. Add i t i onal NO control can b e achieved by X inc reas ing the amount o f exhaus t - gas recyc le , by adding an NO - reducing X cataly t i c converter t o the exhaus t sys t em , or by a comb inat ion o f both techniques . - 25 � Digitized byGoogle 

To approach the 0 . 4 g /mil e NO l evel with a conventional spark- x igni tion engine , a combination of both t echniques app ears to be requi red . The use o f l arge amounts of EGR (20 percent or more) result s in a large fuel -economy pena l ty , s ever e dr i veability problems wi th att endant s afety hazard s , and an increa s e in engine HC and CO emissions. I t i s no t prac ­ tical at this s tage to achieve NO - emi ss ion levels approaching 0 . 4 g /mil e X with EGR alone i n a conventional engin e . Without EGR, engine NO em i s si ons vary between about 3 and 8 g / X mi le , depend ing on the air- fue l ratio , s park t iming , engine s i z e , and other details o f engine d e s i gn and operation . In the dua l -cataly s t sys ­ tem, a s eparat e NO -reduc tion cataly s t i s added to the exhaus t sys tem, X between the engine and the oxidation catalys t . In the three-way cat a lys t system, a s ingle catalytic converter s imul t aneous ly reduces the concen­ tration o f a l l three pollutant s (HC , CO , and NO ) in the exh au s t stream . X Air - fuel ratio must be c l o s e ly regulated in such sys tems . The NO - X reduc t ion cata ly s t s currently avai lab le , as wil l be des cribed below, are not ab le to retain s ufficient activi ty over extended mil eage to reduce these engine emis s ions below the 1 9 7 6 s t andard s . Thus , unl e s s further fmprovement s in NO catalys t d urab i l ity occur over the next year , only X systems for conven t iona l engines with increa s ed EGR and an NO - reduc - x tion cat a ly s t show any promi s e o f approaching the 0 . 4 g /m i l e level . To minfmize demands on cat alyst s i z e , cos t , and durabi l ity , there is a cont inuing empha s i s on achieving low and s tab l e engine emi s sions . Tech ­ ni ques for contro l l ing emis s i ons during the first part of the test when the engine i s s t i l l cold , fuel -mete r ing r equ ir ement s , EGR systems, and the potent i al for fmproved engine emi s s i ons control are examined next . 3.3.2 Cold-S tar t Emi s s ion Contro l s With 1975 - 7 6 c a ta lyst -bas ed emission-control systems, a large port i on of the carbon monoxide and hydrocarbon emi s s ions occur during the cold - s tart and en gine warm-up pha s e of th e drive schedule in t h e CVS -CH tes t . To c ompen s at e for the low vol at i lity of cold gasoline, a - 26 - Digitized byGoogle 

rich mixture mus t b e provided during cold s t art s . The exc es s fuel i s not ful ly burned i n the combus tion chamb er , and the c o ld engine thus emi ts high l eve ls of hydrocarbons and carbon monoxide . Becaus e the oxidiz ing cataly s t i s inefficient whi l e cold , large amount s o f these contaminant s are dis charged to the atmosphere . Al though the NO c ata- x lys t i s a l s o cold and ineffec tive during s t art-up , c o ld - s tart NO emis ­ x s ions tend to b e lower b ecause rich mixtures and cold cyl ind er wal l s reduce the formation o f NO • X B ecaus e o f the h igh HC and CO emis s ions during the c o ld s t art , cons iderab le development effort has b een spent in a number o f c o ld - s tart control s and proc edures . In the prototypes of their 1975 and 1 9 7 6 sys ­ tems , mo s t manufac turers have elected t o modi fy the cold - s tart proces s . Spec i fica l ly , they have achi eved s tart -up with leaner air- fuel mixtures by preheat ing the air and fue l , by improving the mixt ure c ontrol in the carburetor , and by shortening the choking period without serious ly im­ pairing cold engine operation and driveab i l i ty . Mos t prototypes inc l ude air and fuel preheat sys t ems and modi fied choke operation . The purpos e o f preheating air and fuel i s to achi eve higher volat i l i ty with c o ld fuel , which , in turn , a l lows leaner engine opera­ tion and shor ter choking period during warm-up . The air preheat sys tem that has been incorporated in mos t 1970 and s ub s equent American-make cars , and has proven reliab le , wi l l be used in mo s t 1 975 - 7 6 model s . In addi tion to heating the intake air , s everal propos ed emi s s ion­ control sys tems promote further evaporation o f the fuel by supp lying heat to the bas e of the carburetor . Thi s is accomp l i shed by us ing a heat exchanger between the carburetor and the exhaus t-mani fold cro s s over , caus ing the fuel drop lets t o make c ontac t with a hot sur face and to flash into vapor . Several prob lems remain to be solved to ens ure that produc tion uni ts can at tain the emis s ion reduction predic ted by experi ­ mental des igns . Whi le durabi lity o f the sys tem has not yet been evalu­ ated , there appear to be no maj or technical d i fficul t i e s . - 27 - Digitized byGoogle 

A quick-ac t ing choke , emp l oying elec trical or mechanic a l timing d evices , wi l l be u s ed to lean out the mixture as ear ly as pos s ib le after s tar t - up . For sys tems incorporating air and mixture preheating , choking times have been reduced from s everal minutes to l es s than 30 s econd s , whi l e maintaining adequate driveab i l i ty . 3.3.3 C arburetors The prec i s e metering o f the fuel and air to automotive eng ines has become much more important in rec ent years because the mixture ratio is a cri t ical parameter a ffecting the exhaust compos i t ion and the func ­ tioning o f exhaus t - treat ing d evices . Mos t 1 9 7 5 - 7 6 mode l carburetors have been redesigned to achieve better air- fuel ratio contro l and main­ tain good c o ld - s tart performance of the engine . Except for the demand s d uring extreme acc e l erations and dec e l era­ tions , the newly designed carburetors are capab le o f maintaining t oler­ anc es o f ± 3 percent o f the set air - fuel rat io . Thi s approaches the fuel -metering acc uracy requ ired for the dual -cataly s t 1 9 7 6 contro l sys tems in which the air- fuel rat io mus t be held between about 13 . 8 and 14 . 5 to achieve adequate NO reduc t ion in the firs t cata lytic converter . X Cons iderable des ign work remains to b e done to ensure d urab i l ity with the s e finely adj us ted carburetors . Mos t manufac turers are cons id­ ering fac tory - s ealed , tamper -proof setting s b ecause i t i s beli eved im­ pos s ib l e for a typical mechanic to make the requi red ad j us tment s . The depend abi l i ty o f the s e factory - s e t ad j us tment s i s unknown. 3 .3.4 E l ec tronic Fuel In j e c t ion S everal companies are cons idering E l ec troni c Fuel Inj ection (EFI) as an a l ternative to the carburetor . In s uch sys tems , an e l ec ­ tronic module contro l s the amount o f fue l provid ed t o the engine . - 28 - Digitized byGoogle 

An advantage o f e lec tronic control is tha t , by us ing appropriate transd ucers , air- fue l ra t io can be compens a ted for var i a tions in s uch opera t ing parameters as eng ine s peed , manifo l d va c uum , amb ient cond i­ t ions , var ious eng ine tempera ture s , exhaus t compos it ion , etc . Thus , there is po tent ia l for ade q uate contro l o f mixture ra t io over a wide range o f operat ing cond i t ions . EFI sys tems can res pond q u ickly to change s in opera t ing cond i t i ons and are there fore ab le t o provide s a t ­ is fa c t ory control o f a ir- fue l ra t i o under trans ient cond i t i ons . However , cont a c t s mad e with carburetor manufa c turers , automob ile manu fac t urer s , and producers o f e lec tronic fue l inject ion equ ipment ind icate tha t cur­ rent EFI sys tems do no t provide s ub s tant i a l improvement in a ir - fue l con­ tro l over the advanced-de s ign carbure tors opera ted under s teady cond i ­ t ions . E F I sys tems have been and a re in prod uc tion on severa l European cars . Fie ld experience wi th the se sys tems ini t ia l ly showed a high com­ ponent - fa i l ure rate , a l though per forma nce is improv ing . The advantage of EFI over current carbure tor s in sma l l cars is in per formance charac­ teri s t ic s and fue l e conomy , i . e . , Incre ased power out put , p a r t i cu l a r ly for high- rpm high-per formance engine s Be t ter fue l economy for high - s peed driving Improved drive ab i l i ty , part icula r ly with manua l shi ft engine s A t le a s t one manu fa c t urer i s introduc ing a mechani ca l ly con­ tro l led fue l - inj e c t ion sys tem which may show per formance comparable wi th the improve d E F I sys tem a nd a t s avings in cos t . 3.3.5 Exhaus t - Ga s Recyc le (E GR ) The mo s t extens ive ly deve loped te chniq ue for reduc ing engine NO emi s s i ons i s the re cyc l ing o f a fra c t ion o f the exhau s t to the X - 29 - Digitized byGoogle 

engine intake . The recyc l ed exhaus t gas es d i l ute the fresh mixture , thus reducing p eak c ombus tion t emperatures and NO - formation rates . The X d i s advantages o f EGR are the los s in engine power and the reduc tion in tolerab l e air- fuel ratio variations consi s tent wi th smooth engine opera­ tion. The us e o f EGR requires some mixture enrichment to maintain ad equate driveab i l i ty , which results in a fuel -ec onomy penal ty . In most sys tems , EGR i s cut out at wide-open throttle and id l e operat ion . EGR was introduced in mos t 1 97 3 mode l year vehic les to bring NO X below 3 g /mi l e . Experienc e from the durab i lity t e sting o f these EGR sys t ems ind i cates that plugging o f the recyc l e l ine and control valve wi th l eaded fuel s is a signi ficant prob lem. But wi th unl eaded fuels , and wi th regular inspection and c l eaning o f the sys tem, these prob lems are not expec ted to b e s evere . As the amount o f EGR is increas ed to reduce NO engine emis s i ons X below 3 g /mi le , there i s a need for more precise matching o f the recyc le flow t o fresh mixture flow , and for more uni form mixing o f the recyc led exhaus t in the intake . Engine combus tion-chamb er redesign with higher turbulence l eve l s to promote more rapid c ombustion also improves the tol erance of the engines to EGR . 3.3.6 Po tential for Engine Emis s ion Reduc tion The methods of emis s ion reduct ion discus s ed s o far have b een engine mod i fications that reduce emis s ions from the bare engine , i . e . , b e fore after-treatment devices s uch as catalys ts and thermal reactors . The firs t two rows o f Tab le 3 - 2 give typi cal engine emis s ions from a General Motors Corporation 1 9 7 2 production audi t . Both mean emis sions and the s t andard d eviation are given . The magni tud e o f the s tandard d eviation ind icates the spread in emis s ions about the mean value . This spread i s due to d i fferenc es in items s uch as brake s etting , variations in transmi s s ions , engine fric tion , carburetor settings , and s tacking up - 30 - Digitized by Coogle 

TABLE 3·2 Engine Emi s s ions at Low Mileage : Mean and S tandard Devia t io n Emi s s ions in gr ams/mile ( a ) 1!9. co NO � mean (S . D . ) mean (S . D . ) mean (S . D . ) (b ) GM 19 72 production ( audit 1. 7 ( 0 . 64 ) 22 (8 . 3 ) - 4 (,vl ) c ) Bes t GM divis ion ( ) 1972 product ion 1. 2 (0 . 32) 16 ( 6 . 2) - 4 (,vl ) c ( d) Potential bes t engine emi s s ions , lean carburetion 1 ( 0. 15 ) 10 ( 3) 2. 5 (e) Potential best engine emiss ions , rich carburet ion 1.5 25 1.5 (a) l972 cvs-c tes t procedure (b ) 3656 vehicles tes ted (c) California 7 -mode tes t emiss ions multiplied by 2 (d) Standard-s ize engine , s tandard-s ize car , with quick heat manifo ld , improved carburetor , quick acting choke , and EGR <•> same as (d ) and with a ir inj ection into the exhaus t manifold - 31 - Digitized byGoogle 

o f engine toler anc es . The bes t GM d ivis ion has been abl e to reduce both mean engine emis s ions and the spread in emis s ions through improved produc tion c ontrol , as indicated in the s e c ond row of the tab l e . W i th the add i t ion o f a quick-heat mani fold and an improved car­ buretor with a quick-ac t ing choke , the s e HC and CO engine emis s ions can b e improved . However , us e o f EGR to reduce NO emis s ions requi res some X mixture enrichment to compensate for the decreas ed f l ame speed , and engine HC and CO emis s ions ri s e . The las t two rows in Tab le 3-2 are e s timates of achi evab le engine emis s ions goa l s at l ow mileage for s tan ­ dard - s i z e engines in s tandard - s i ze vehic l es . The thi rd row correspond s to a lean and the fourth row to a richer carburetor s e t t ing . The fur ­ ther reduc tion of emi s s ions i n c onventional engines mus t be achi eved with exhaus t trea tment , such as cataly s t s or thermal reac tors . 3. 4 Catalys ts The control sys tem for 1976 on which mos t d evelopment ef for t has been concentrated uses two cataly s t beds t o c l ean up th e engine emis s ions before exhaus t to the atmosphere . A typical sys tem layout is shown in F igure 3 - 1 . The bed c lo s e s t to the engine is u s ed to remove NO • I t i s operated under net reduc ing exhaus t -gas c ondi tions X (between 1 and 2 p ercent carbon monoxide in the exhaus t gas , corres pond - ing t o a s l ight ly rich carburetor cal ibration) . Air i s then added t o the exhaus t s tream between the cataly s t bed s , and the remaining HC and CO emi s s ions are removed in the s econd cataly s t , the oxidat ion bed . The two catalytic beds may be in separate containers as shown in the figure , or they may be packaged in a s ingle container . The sys tem i s a logical development of the 1 9 7 5 control sys tem described previous ly . Becaus e the NO c ataly s t bed mus t be p l ac ed ahead o f the oxida- x t ion bed , the oxidat ion catalys t warms up more s lowly . Contro l o f HC and CO emis s ions d uring s tart -up would thus be delayed i f air were always inj ected b etween the c atalys t b ed s . To maintain control over - 32 - Digitized byGoogle 

F I G U R E 3. 1 TYPI CAL DUA L-CATA LYST SYSTEM IIPIOYED CAIBUIETIOI AID CHOKE AlTITUDE AIID TEIPEUTUIE COIPEISATIOI HC-CO OIIDIZIIS COIYEITEI I EXHAUST SA$ w IECIICULA TID I w �� All IIJECTIDI PUlP I01 IEDUCIIS COIYEITEI 0 lEACH SIDE) cCi ;:+ N CD Q. ELEcta. ICIIITIDI rr '< C) 0 � """""" rv 

1 9 7 6 HC and CO leve l s , air i s diverted to up s tream o f the NO -reduc tion X bed d uring the eng ine-warm- up phas e . Thus the NO bed can ac t ini tially X as an oxidat ion cataly s t . Once the oxidat ion catalyst i s warmed up , the air i s d iverted to between the two beds and the firs t catalys t ac t s primari ly as an NO -reduction catalys t . (As a n a l ternative , a " s tart" X cataly s t can be us ed ahead o f the NO cata lys t and bypas s ed after the X eng ine is warm . ) The oxidation catalys ts u s ed in the s e dual -catalys t sys tems are the catalys t s now being developed for 1 9 7 5 model year vehic les . These cons i s t o f nob le meta l s (platinum and / or pal ladium) or bas e metal s pro­ mot ed wi th nob le metals (a sma l l amount of nob le metal required to ini ­ tiate ac tivi ty) depos i ted on both mono l i thic and pel let s ubs trates . Except for prec i o us metals , there appears to be no prob lem o f s upp ly of raw material s for the ac tive ingred ient and the support in the catalys t s c ontemp l ated . The early s tate o f d eve lopment o f oxidat ion catalys t s was described in the previous Committee report . S everal companies now have produc t s that have demons trated ad equate ini tial activi ty , and some o f thes e have reasonab le d urab i l i ty . The NO cataly s t s tes ted t o date inc lud e nob le meta l s (p latinum, X ruthenium , pal lad ium) , base metal s , or base metals promo ted wi th noble meta l s , depos i ted on both monolithic and pel leted ceramic s ubs trates . Nickel-copper and Inconel metallic mono l i thic NO cataly s t s are a l s o X being tes ted . Reduc tion catalys ts are genera l ly les s wel l developed than oxidation catalys ts . Whereas s everal NO cataly s t s have demons tra- x ted sufficient initial ac t ivity , the l imi ted amount o f durab i l ity data c urrent ly avai lab le i s no t encouraging . S everal examp l e s o f the best low-mi leage emis s ion data avai lab l e are shown in Tab le 3 -3 . Only a few 1 9 7 6 experimental vehic les have been tes ted to evaluate NO catalys t durab i l i ty . Be fore attemp ting extensive dura­ x b i l i ty tes ts , mo s t manufac turers are working to op tfmize the p er formance o f the sy stem to reduce l ow-mi leage emis s ions to values at lea s t 5 0 - 60 - 34 - Digitized byGoogle 

TABLE 3-3 Examples o f Best Low Mileage Emis s ions Measurements with Dual-Catalys t Sys tems on Experimental 19 76 Vehicles Company Engine a Vehicle EGR Emissions in g/mile Catalys t Data We ight S ize Lb . ill 1!£ £Q NO --x (a) HC/CO (b) NO --x American Motors 25 8 0. 27 5.7 0 . 55 Esso 4500 35 0 No 0 . 09 1.0 0. 2 ( a ) Enge lhard (b ) Gould GEM Volvo 3500 85 Yes 0 . 19 2.2 0.4 ( a ) Base , Pe llet (b) Base , Pe llet 3500 85 Yes 0 . 41 3.4 0 . 38 (a) Noble , Monolith (b ) Noble , Monol ith - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- l,o) Vt General Motors 4500 350 Yes 0 . 24 1. 7 0 . 15 ( a ) UOP , Platinum, Pellet (b) Gul f , Monolith 4500 350 Yes 0 . 42 3. 1 0 . 21 ( a ) A ir Products , Pe llet (b) Gul f , Pellet 4500 350 Yes 0 . 17 1.0 0 . 19 ( a ) UOP , Platinum, Pe llet (b) Johnson-Matthey , Monol ith 4500 350 Yes 0 . 21 1. 0 0 . 22 ( a ) UOP , Platinum, Pel let (b) Johnson-Matthey , Mono l ith 0 4500 350 Yes 0 . 37 1. 8 0 . 27 ( a ) UOP , Platinum , Pellet <6" ;::+ (b) GM , Pe llet N. CD Q. rr '< Chrysler 360 No 0. 17 3.0 0.5 (a) ( b ) Noble , Monol ith C) 360 No 0 . 23 2.5 0.52 (a) 0 (b ) Base & ,...._ 360 Yes 0 . 34 3.9 0 . 44 (a) (b ) Noble , Pellets (\) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 

�BLE 3-3 (Cont ' d ) a Company Vehicle Engine EGR Emiss ions in slmile Cata lys t Data Weight S ize Lb . CID HC - co - NO (a) HClCO; (b) NO --x � Ford 4000 250 No 0 . 45 2.9 0 . 38 ( a ) Engelhard , Monol ith (b ) Promoted Base , Pel let 5 000 35 1 No 0.43 2.4 0 . 27 ( a ) Engelhard , Monolith (b) Gould , GEM 4000 250 No 0.52 3. 7 0 . 39 ( a ) Engelhard , Monol ith (b) ICI , Pel le t 5000 35 1 Yes 0 . 48 3.3 0 . 39 ( a ) Engelhard , Monolith (b) ICI , Pellet Daimler-Benz 350 Yes 0 . 20 1.4 0 . 33 (a) Chemico , Base , Pe llet (b) Chemico , Base , Pe llet Yes 0 . 15 1. 2 0. 3 (a) Noble , Monol ith I (b) Nob le , Monol ith l,.o,) 0\ Nissan 2 750 Yes 0 . 1- 0 . 4- 98 0. 2 1.2 0. 3 (a) ( b ) Johnson-Ma tthey , Noble, Monolith Johnson-Mat they 2700 llO No 0. 17 1.8 0 . 25 ( a ) Johnson-Matthey , Noble , Ricardo Monolith (b) Johnson-Matthey , Noble , Monolith 0 <6" b ;::+ Volkswagen 2500 98- 104 Yes 0 . 38 2. 2 0 . 64 ( a ) Monolith, Noble N. (b) Monolith , Nob le CD Q. b rr '< 2500 98-104 Yes 0 . 49 4. 9 0 . 46 ( a ) Monolith, Noble (b) Monolith , Noble C) 2500 98- 104 Yes 0 . 82 4. 0 0.57 ( a ) Monolith, Noble 0 (b ) Monolith, Noble & ,...._ (\) 

�BLE 3-3 (Cont ' d ) a Company Vehicle Engine EGR Emis s ions in sLmile Catalys t Data Weight S ize Lb . CID - !!£ £Q NO --x (a) HCLCO; (b) NO --x b Toyota 2500 97 Yes 0 . 39 2. 7 0.5 ( a ) Pallad ium , Pe llet (b ) American Oil , Base , Pellet b 2500 97 Yes 0 . 29 3.0 0 . 54 ( a ) Pa llad ium, Pellet (b) American Oil , Base , Pellet 2500 97 Yes 0 . 39 3. 7 0 . 39 (a) Palladium, Pe llet (b) Toyota , Platinum, Pellet Note : a - 1975 CVS -CH test procedure . Data usua l ly averages o f severa l tes ts . b - Emiss ion- control sys tems include a manifold thermal reactor be fore the NO - reduct ion catalys t . X \,) ...... 0 <6" ;::+ N. CD Q. rr '< C) 0 & ,...._ (\) 

perc ent below the 1 9 7 6 s t andard s leve l s , to improve vehi cle driveab i l ity , and to hold performanc e l o s s e s t o a minimum . S ince NO -cataly s t dura- x b i l i ty i s sub s tant ia l ly inferior t o that o f the b e s t oxidat ion catalys t s , a product ion goa l o f .25 g /mi le does not s eem unreas onab ly s tringent . The res u l t s o f the mos t promi s ing durab i l ity t e s t s o f s ome dual­ cataly s t vehic les are s ummar ized in Tab le 3 -4 . Emi s s ions are shown as a func t ion o f mi l eage . Where engine -emi s s ions data are avai lab l e , the average catalys t-convers ion e f fi c i enc ies over the entire CVS -CH driving cyc le c an be e s t imated and are shown in the tab l e . Convers ion e f f i c i ency is the perc entage of entering emis s ions removed in the converter . The s e data s h ow that the ini tial high c onvers i on e ffic iency rap id ly deteriorates . The causes o f thi s rapid deterioration in NO -cataly s t e f f i c i ency X are no t yet quant itatively under s tood . Cata ly s t s have a long h i s tory o f succes s i n the petro leum and chemical ind us tries ; the maj or proces s e s i n these indus tries emp loy s t eady - s tate cond i tions o f temperature , pres ­ s ure , and flow rate o f gas es , wi th careful exc lus ion o f poi s ons . Many automob i le catalys t s deve loped today would work s imi larly we l l and pro ­ b ab ly las t 5 0 , 000 mi les i f they could work within narrowly defined oper­ a t ing ranges ( or "windows " ) in each of four vari ab les : t emperature , gas compo s i tion , gas f low , and poi s on conc entrat ions . Catalys t s c an tolerate occas ional excur sions from these windows , but pro longed excur­ s ions invar iab ly lead t o s low chronic aging or quick mas s ive fai l ures . In actual prac t ic e , an automob i l e i s always in a trans ient con­ d i tion : the cataly s t i s too co ld during s tart -up and too hot during a long down-hi l l cruis e ; the air- fue l ratio i s too rich on idle and too l ean dur ing high speed ; the exhaus t -gas flow i s s low during id le and fas t during upgrade crui s e . The cataly s t s are a l s o exposed to repeated cyc les o f heating and coo l ing , evaporation and condens at ion o f water , pul s ating flow from exhaus t gas e s , vigorous shaking on the road , and a variety o f poi s ons inc l ud ing lead and sul fur . Under thes e excur s i ons from the windows , cataly s t s d eteriorate rapidly . - 38 - Digitized byGoogle 

TABLE 3 -4 Emissions As Funct ion of Mileage for Durabi lity Tests on Dual-Catalys t Sys tems b c Catalys ts Emis sions , g/mile NO Catalys t E ffic iency ---x Manufacturer, (a) HC/CO Vehicle a (b) NO Mileage HC - co - NO percent --x GENERAL MOTORS d ( l ) 4500 pounds ( a ) UOP , noble , 0 0 . 22 78d 350 C ID pel le t . 1000 0 . 32 1. 7 0 . 42 5 8d Chevrolet ( b ) Gul f , noble , 7000 0 . 39 3.0 0 . 45 55 d EGR pelle t . 13000 0.52 4. 8 0 . 73 27 d (2) 4500 pounds ( a ) UOP , noble , 0 0 . 21 1.0 0 . 21 79 d 350 CID pel le t . 7000 0 . 47 1.8 0 . 59 41 Chevrolet ( b ) Johnson-Ma tthey , EGR noble , monol ith . d w ( 3) 4500 pounds ( a ) UOP , noble 0 0 . 36 1.8 0 . 28 72 \Q d 350 CID pellet . 4000 0.57 4. 1 0.51 49 Chevrolet General Motors EGR Research , pelle t . � ( l ) 5000 pound s ( a ) Engelhard , mono- low 0. 3 1.5 0.56 78 35 1 CID l ith . 3000 0 . 33 1.5 0 . 49 80 0 Ford (b) monol i th . 6000 0 . 48 2. 6 0 . 70 71 <6" EGR 9000 0 . 72 1.9 0 . 89 63 ;::+ N. 8-10 grams o f 12 000 0 . 66 3.6 o . 75 64 CD Q. platinum, e dual- 16000 0 . 66 5.4 1.3 46 rr '< bed converter . 20000 0 . 82 3. 8 1.5 37 C) ( 2 ) 5000 pounds ( a ) Pe lle t low 0 . 35 3. 8 0 . 68 70 0 35 1 CID Ford (b) Pe llet 1000 2000 0 . 61 0 . 59 3.3 3. 6 0 . 99 1 . 25 & EGR f Dual-bed 6000 0 . 68 4. 2 1 . 72 25 ,...._ converter (\) 

�BLE 3-4 (Cont ' d ) b c Catalys t s Emis sions , g/mile NO Catalys t E fficiency X Manufactur g r , ( a ) HC/CO Vehicle (b) NO � Mileage !!£ £Q NO --x percent FORD (Cont ' d) (3) 4000 pound s (a) - low 0. 52 3. 7 0 . 39 89 250 CID (b) ICI , pellet 4000 0 . 65 5.2 0 . 48 86 Ford No EGR NISSAN ( 1 ) 2750 pounds (a) Noble , pe llet 0 0 . 19 0.5 0 . 28 70 9 8 CID , EGR (b) Johnson-Mat they 3000 0 . 32 1.1 0. 7 37 noble , monol ith 7300 0 . 34 1. 7 1.1 6 13900 0 . 67 2. 7 1.1 (2) 2 750 pound s (a) Noble , pellet 0 0. 1 0.4 0. 3 84 � 0 98 CID , EGR (b) Johnson-Matthey 5 200 0 . 33 2. 2 1.3 30 noble , monol ith (3) 2750 pounds ( a ) Noble , pe llet 0 0 . 17 1. 2 0 . 27 67 98 e m , E GR (b) Johnson-Mat they 3100 0 . 38 1.8 0.5 38 noble , monolith - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - - - - ----------------- - - - - - - -- - - - - - - - ------- - - - - - -- - - - ---- - - - - - - - - - - - - - - - - -- - - - - - - - - - TOY� (1) 2500 pounds (a) Pallad ium, 0 0 . 39 2. 7 0.5 g 0 9 7 CID pe llet 12000 0 . 46 2. 8 0 . 82 g <6" Reactor , EGR (b) American Oil , 20000 0 . 50 3. 1 0 . 93 ;::+ N. base , pellet CD Q. rr '< (2) 2500 pound s ( a ) Pal ladium, 08 0 . 29 3. 0 0 . 54 9 7 CID pellet 120008 0 . 49 3.5 0 . 81 C) Reactor , EGR ( b ) American Oil , 28000 0.52 5.7 1.5 0 base , pel le t & ,...._ (\) 

�BLE 3-4 (Cont ' d ) b Catalysts Emiasions , g/mile 1!Q_ Catalys t E ffic iency c A Manufacturer , ( a ) HC/ CO Vehicle a i.!U..1fQ Mileage !!£ £Q � percent TOYOTA (Cont ' d) (3) 2500 pound s ( a ) Pa llad ium, 0 0 . 39 3. 7 0 . 39 9 7 CID pellet 4000 0 . 45 4. 2 0.51 Reactor , EGR (b) Toyota , 8000 0 . 40 4.3 0 . 94 p la t inum , 12000 0.59 4.4 1 . 09 pe llet 16000 0 . 31 4. 3 0 . 38 a - Emis s ion Control System includes engine modi ficat ions , air pump , NO catalytic converter , oxidation cataly t ic X converte r , and EGR and manifold reactor where note d . b - 19 75 CVS -CH test procedure . c - NO cataly s t e fficiency is percent NO removed in cataly t ic converter . X X � d - NO catalyst e fficiency e s t imated from approximate engine NO emiss ion o f 1 gram/mile . X X ...... e - - Cataly s t judged by vendor not to be ava ilable in commercial quantitie s . f - E GR sys tem fa ilure . g - Emiss ions a t these mileages measured a fter ma intenance . 0 <6" ;::+ N. CD Q. rr '< C) 0 & ,...._ (\) 

The rat e o f the deterioration due to inad equate c ontro l o f air­ fuel ratio in the engine and the temperature fluc t uat i on in the cataly s t b ed has no t b een quant i f ied . Thermal d egradation o f the catalyst can occur due to damage to the s ur fac e s tructure cau s ed by overheat ing . The presenc e of an oxidiz ing atmosphere even fo r short period s o f time when the cataly s t i s hot i s known to be detriment al , espec i a l ly to the nicke l­ copper al loy meta l lic catalys t s . The lo s s o f catalyt ic material both from nob le metal and b a s e metal NO cataly s t s has a l s o b een obs erved to X occur , prob ab ly d ue to oxidation . I t i s c lear that po i s oning o f the ac tive cataly s t materi al by contaminant s in the fuel i s the cause o f s ome d eteriorat ion . Dur ing the las t two years , it has become evid ent that the oxidat ion cataly s t s being t e s t ed i n 1975 prototype vehic les deteriorate as a consequenc e o f the trace quant i t ies o f lead , phosphorus , and o ther e l ement s i n lead­ free fuel s and lubricant s . I t i s ant ic ipated that , as a res u l t o f EPA * regu lat ions , the lead - free fuel availab le in 1 9 75 and 1976 wi l l have average contaminant leve ls of about 0 . 03 grams/gal lon lead , les s than 0 . 005 grams/gal lon phosphorus , and ab out 0 . 04 percent sul fur by weight . I t i s no t known how s everely these c ontaminant l eve l s wi l l a f fect the ac tivi ty of the d i fferent NO cataly s t s now being eva luated . Laboratory X t e s t s on a nob le metal NO catalys t which c ontained p lat inum and o ther X metals showed l ead poi s oning o f magni tud e c omparab le t o that ob s erved with p l a t inum oxidation catalys t s . S u l fur a l s o a ffec ted the ac t i vity of thi s NO catalyst at leve ls of 0 . 04 percent by weight or more . How- x ever , a ru thenium NO cataly s t appeared in b ench t es t s to b e much more X res i s tant t o lead poi s oning . There are NO cataly s t s o f both nobl e X metal and c opper-nickel that are remarkab ly res i s tant to lead leve ls up to 0 . 5 gram/gal lon . NO catalys t s may have the ab i li ty t o par t i a l ly X recover from s u l fur poisoning i f operated in an oxidiz ing atmosphere at high t emperatures . *In a propos ed ru le-making , EPA has recommended maximum cont aminant l eve l s of 0 . 05 grams/gallon lead and 0 . 0 1 grams/gal lon phosphorus . I t i s a s s umed that average contaminant leve l s wi l l b e about half the maximum leve l s . - 42 - Digitized byGoogle 

The abi l ity to c ontrol air- fuel ratio within narrow limi ts with dual -cataly s t systems is cri t ical . I t i s wel l known that , under certain operating cond itions , nitric oxide , NO , is reduced in the NO -cataly s t X b ed t o ammon ia , mo s t o f which is then oxidized back to NO in the oxida- t ion catalys t . Ammo nia formation increas es with carbon monoxide l evel in exhaus t mixtures . Thus , whereas the air - fuel mixture mus t b e s light ­ ly fue l - r ich t o provide net reducing c ond i tions at the NO -cataly s t bed , X too great a CO level leads to exces s ammo nia formation and resul t s in increas ed concentrations of NO in the exhaus t . It appears that the air­ fuel ratio mus t be c ontrolled t o give about 1 to 2 percent CO in the exhaus t , corresponding to an air- fuel ratio of 13 . 8 to 14 . 5 . Progres s i s being mad e in the deve lopment o f NO cataly s t s for X automo t ive us e . However , to retain i t s e f fec tivene s s , i t i s neces s ary that the catalys t be integrated into the engine - emi s s ion-contro l system t o pro t ec t the cataly s t from l ong excurs i ons from i t s operat ing windows . Unfortuna t e ly , coordination o f res earch by the automob i l e manufacturers and c atalys t s upp liers is far from ideal . The compos i t i on of the cataly s t s upp l i ed to th e auto manufacturer for tes t ing is proprietary to the cataly s t s upp l i er ; when fai lures oc cur during durab i l i ty t es t ­ ing , the cataly s t mus t be returned to the cataly s t s uppl ier for further analys i s . 5 0 , 000 -mi le durab i lity tes t ing requires three to four months , 25 , 000 -mile tes ting t akes s ix to eight weeks . The proc e s s is a s low one . Many months may elap s e from the t ime a cata ly s t is s upp lied to the t ime data may be avai lab le that could lead to an tmproved cataly s t com­ po s i t ion . 3.5 Three-Way Catalys t s S everal cataly s t manufac turers are d eve loping s ing l e -b ed cata­ lys ts tha t , under care f u l ly c ontrol led opera ting cond i t ions , wi l l s tmu l ­ taneous ly promote oxidation o f HC and C O and reduction of N O • X - 43 - Digitized byGoogle 

S ucce s s ful opera tion o f s uch a three -way ca t a lys t ha s been found to occur in a narrow window of a ir - fue l ra tio , s l igh t ly on the * rich s ide o f s toichiometry . The width o f thi s window ha s bee n found to be only ± . 1 a ir - fue l ra t io , thus re quir ing an ove ra l l contro l o f a ir- fue l ra t i o to wi thin le s s than + 1 percent . Lean- s ide devia t ions from this window re s u l t i n a dra s t ic l o s s o f NO convers ions ; r i ch- X s ide deviat i ons lead to cons iderab le lo s s o f HC a nd C O oxid a tion e f fi- c iencie s a nd increa sed ammonia forma t ion . The d i f ficu l t ie s of ma int a in­ ing such a close contro l o f a ir - fue l ra t i o d ur ing a l l the trans ient cond i t ions tha t oc cur during typ ica l opera t ion of an a utomob i le have been c i ted in S e c t ion 3 . 4 . I f a three -way cata lys t could be s ucc e s s ful ly incorpora ted into a ve hi c l e and prove d to pos s e s s adequa te durab i l ity , a s imp ler sys tem than the d ua l - ca t a lys t sy s tem wou ld re s u l t . S ince there is enough oxygen pre sent in the exha u s t ga s , the air pump would no longer be re q uired . One ca ta ly s t bed wou l d be e l imina ted , and the d i f ficul t ie s o f he a t ing u p the cata lys t bed s rapid ly t o contro l cold - s tart emi s s i ons would be s imp l i fied . Vehic le driveabi l i ty is known to be good wi th a s toichiome tric a i r - fue l mixture , a nd the fue l economy for a g ive n engine would be rea sonab ly c lose to opt imum . 3.6 Feedback Contro l for A i r - Fue l Ra tio The need for more c lose contro l o f exhau s t -ga s compo s i t ion both in the d ua l - c a t a lys t a nd the 3-way ca t a l y s t sys tem ha s led t o the in­ ve s tigat ion o f me thod s o f achiev ing more pre c i se fue l and air me ter ing . A method tha t ha s me t wi th some s ucce s s and i s und er deve lopment in severa l E uropean and Ame r ican companie s i s a fe edback , or c lo s e d - loop , sys tem o f fue l me ter ing . In such a sys tem, an oxygen sensor is used to de tect the leve l o f oxygen in the exhaus t s tream a nd to s up p ly *The s t o ichiome t r i c a ir - fue l r a t io is the theore t i ca l ra tio for comp lete comb u s t ion . - 44 - Digitized byGoogle 

an error feedback s i gnal ei ther t o an e lec tronic fuel - inj ect ion (EFI) contro l module or to a s p ecial ly c ons truc t ed carburetor . Thi s s i gnal cau s es ad j u s tment s in the fuel or air s upp ly , thereby maintaining c lo s e contro l o f air- fuel rat io . Unfortunately , thes e oxygen s ensors funct i on only when hot and are thus ine f fect ive in control ling cold - s t art emi s ­ s ions . B ecau s e the oxygen s ens or i s an electrical transducer , i t i s parti cu larly we l l suited for adaptation t o the electronic c ircuitry o f the EFI c ontro l module . Also , fue l - inj ect i on sys t ems provid e quicker respons e to error s i gnal s than do carburetors . The EFI sys t em or car­ b uretor u s ed mus t be ab l e to control air- fuel ratio t o within + 5 per­ cent of s toichiometry wi thout feedback ; the s ensor feedback sys t em at present has l imited control authori ty s o that it canno t c orrect for deviat ions outs ide thi s range . C urrent EFI sys t ems and advanc ed car ­ buretors can achi eve this degree o f air- fuel ratio c ontrol during s t eady - s tate operation , but d eviate s i gni ficantly out s id e the ± 5 per­ c ent range dur ing trans ient vehicle operation such as ac ce leration and deceleration . To obt ain ful l b enefit from the s ensor- feedback sys t em , improvement s i n the performance o f the basic EFI or carburetor wil l be required . The s ensor i s expec t ed t o be inexpens ive and a l i fe of about 12 , 000 mi les is the development target . The s ensor could then be exchanged as a spark p lug . The durab i l ity o f oxygen s ensors now avai lab le i s inad equat e , and their l i fe i n a vehic le i s only a few hours . The maj or prob lems are thermal shock , eros i on o f the electrodes , and maint aining good elec trical contac t s wi th the s ensor . In add i tion , b ench t es t s have shown that the s ensor can be poi s oned by l ead , s ul fur , phosphorus , and o ther impur i t i e s . Con s iderab l e development wi l l there fore b e required b e fore the s ensor and feedback sys tem i s ready for mas s pro­ duc t ion . - 45 - Digitized byGoogle 

I f the durab i l i ty and pois oning prob lems are solved , the oxygen s ensor could make an impor tant contribution to lowering emi s s ion l evel s and improve durab i l i ty o f the cataly s t s i n the exhaus t sys tem b y avoid­ ing large variat ions in exhaus t compos i tion and temperature during opera­ t ion of the engine . Development s on feedback sys tems have been proceeding most intensive ly in Europe , where the performanc e gains o f fuel -inj ection sys tems on sma l l er , higher- speed engines are more s i gni ficant . Tes t res u l t s on s ix d i f ferent European veh i c l e s are s umma ri z ed in Tab l e 3 -5 . Al so shown are data from B endix , also wi th a compact c ar . Thes e res u l t s a r e at low mi leage ; durab i lity data are not yet availab le . The s ensor - feedback c onc ep t a l s o c an b e used to control air- fuel ratio , and thus exhaus t -gas comp o s i t ion , with the dua l - c atalys t emis s ion­ c ontrol system. Thi s sys tem is more comp l ex than the three-way cataly s t approach s ince a n a i r pump is required t o s upp ly s ec ondary a i r ups tream of the oxidat ion catalys t , and air mus t be divert ed to up s t ream of the NO -reduc tion catalys t d uring the co ld - s t art por t ion of the t es t . Again , X the eliminat ion of exhaus t - gas composit ion excurs ion s out s ide the des ir- ab l e operating window o f the cataly s t s would b e expec ted to improve cata­ lys t l i fe , and there i s a bet ter chanc e to d evelop s eparat e oxidation and reduc tion cataly s t s by a given t ime than to find a three -way catalys t adequate to the j ob . S everal para llel deve lopment s are neces s ary t o make the oxygen­ s ensor feedback-control cataly s t sys tem more than a promis ing concep t . Firs t , the oxygen s ensor mus t b e shown to b e durab l e in the exhaus t environment o f an operat ing vehicle wi th comme rc i a l ly availab l e l ead­ free fuel s . S econd , the EFI sys tem or carburetor mus t b e improved to provide contro l of air- fuel ratio to within ± 5 perc ent of s toichi o ­ metric for a l l engine operating mod e s , or the effec t ive range o f the feedback sys t em mus t be extended . Fina l ly , either the durab i l i ty o f the cataly s t i n the three-way sys tem mus t b e demons t rated , or a durab l e - 46 - Digitized byGoogle 

TABLE 3- 5 Low-Mileage Emi s s ions from Compac t and European Vehicles Equ ipped wi th Three-Way Catalys t Sys tem Emi s s ions in grama / mile HC co NO -x S ix Volkswagen veh ic l e s with Bo s ch EF I and 0 sensor ; 5% EGR , and nob le me tal 2 mono l i thic three-way ca talys ts . 69- tes t average 0 . 15 2. 2 o. 21 Range 0 . 1 - 0 . 25 1. 1 - 3.3 0 . 1 - 0 . 35 � ...... Bend ix tes t s on 2500- lb vehicle , 1 50-C ID 4-cyl inder eng ine , EF I and o s ensor , 8% EGR 2 6 - te s t average 0 . 24 2. 8 0 . 35 0 Range 0 . 1 8 - 0 . 30 2. 1 - 3. 2 0 . 3 1 - 0 . 37 ca· ;:::;: N. CD a_ o­ '< CJ 0 � ,...._ rv 

NO -reduc t ion cataly s t mus t b e deve loped for the dual -catalyst sys tem . X The effec t s o f fuel c ontaminants and t empera ture f luc tuations on the catalys t ac tivity and s i z e of the required air - fuel ratio operating wind ow are unknown at thi s t ime . 3.7 Thermal Reac tors A s ub s tant ial amount o f work has b een done on emi s s ion-control sys tems that incorpora te a thermal reac tor , a chamber in which HC and CO emis s ions are b urned after l eaving the engine . Typically the reac tor i s b o lted to the cyl inder head in place of the normal exhaus t mani fold , al though s ome sys tems emp loy thermal reac tor s further back in the ex­ haus t sys t em . Some sys tems c omb ine a thermal reac tor wi th catalys t s ; s ome u s e a therma l reac tor a lone . There have b een two bas ic vers i ons o f sys tems us ing a thermal reactor only : fue l -rich and fue l - lean sys tems . The fue l -rich sys t em res ul t s i n l e s s N O format ion , b ut only at the expen s e o f sub s tantia l ly X poorer fue l economy . The l ean sys tem does not require air inj ection , s o i t has the advantage o f being s imp ler . Fuel -rich reac tor car s typ i ­ c a l ly operate in the range o f air- fuel rat ios from 1 1 : 1 to 13 : 1 , whi l e lean reac tor cars operate at air- fuel ratios o f 1 7 to 1 9 : 1 , depend ing upon the degree of exhaus t -gas recirculat ion . The s e ranges of operation res ult in acceptab l e but not always good driveab i l ity . A maj or d i f ficu l ty in therma l -reac tor sys tems has b een achi ev­ ing high enough gas t emperature ins ide the reac tor to burn up the eng ine HC and CO emis s ions . In the rich -reac tor approach , the chemical energy in the exhaus t is u s ed to obtain core gas temperatures o f up to 0 1 800 F. Rich reac tor systems achieve better emi s s ions c ontro l than l ean reac tor sys t ems , but have a much higher fuel -economy penal ty and have more s evere durab i l i ty prob lems b ecau s e o f the higher temperatures . - 48 - Digitized byGoogle 

Sys tems that c ombine one or more thermal reactors wi th cataly t i c converters are also being developed . In mos t o f thes e sys tems , the thermal reac tor bolted to the cyl inder head is us ed to achi eve partial burn- up o f the engine HC and CO emi s s ions to reduce the load on the oxidation cataly s t downs tream . General Motors is d eveloping a reac tor- catalys t comb ination ca l l ed a trip le-mod e sys t em . The aim o f the sys t em i s to avoid damag­ ing the NO and oxidat ion cat a lys t beds by overheating during engine X operation at high load . At about 55 mph vehic le speed , the dua l - cataly s t sys tem i s bypas s ed through a thermal react or . HC , C� and NO emis s ions X from the vehic le are a l l higher during the bypas s mod e . At l ower speeds , the bypas s i s s ealed with a valve . Thi s sys tem has met the 1 9 7 6 s tan­ dard s at low mi leage ; i t s d urab i l ity has yet to b e e s tab l i sh ed . The sys t em is more c omp l i cated than the dual-cataly s t sys t em ; the develop­ ment o f an e f f ec t ive valve i s a formidab l e p rob lem s ince the bypas s mus t b e sealed tight when not in us e ; and the emi s s ions a t high vehi c l e speed are higher than values obtained with the dua l - cataly s t sys t em alone . The c laimed , but yet to be demonstrated , advantage is that cataly s t l i fe would be extend ed by the el imination o f prolonged high - t emperature cata­ lys t operation . Another reac tor - p lus - cataly s t approach i s being deve loped by Que s tor . Their sys tem cons i s t s o f a smal l -vo lume thermal reac tor bol ted onto the cylinder head , in which partial oxidation of engine HC and CO emi s sions o ccurs , fo l l owed by an Inconel 6 0 1 screen NO - reduct ion cata- x lys t , fo l lowed by a final oxidi zing thermal reac tor . Air i s inj ec ted into the exhaus t ports and downs tream o f the NO cataly s t . The engine X i s operated fuel -rich , so there i s a fue l economy pena l ty relative to the 197 1 produc tion tes t vehi c le of 25 percent in s top-and -go driving . Low-mi l eage emis sions are be low the 1 9 7 6 s tandard s , and s ome durab i l i ty has been demons trated . Mi leage accumu lation i s b eing done wi th high ly - 49 - Digitized byGoogle 

l eaded fue l s , and lead poi soning of the cataly s t appears not to be a prob lem. C ataly s t overheating i s c ontro l l ed by water inj ec tion . 3.8 Wankel Engine The Wankel rotary engine i s being deve lop ed by some manufac turer s b ecause i t o ffers the potent ial o f being a smal l , smooth -running , light­ weight , relatively inexpens ive power p lant . Fue l economy o f the bare engine is general ly poorer than that of a p i s ton engine of comparab le power , and there have been durab i lity prob l ems , but d eve lopment i s con­ tinuing . At the pre s ent s t ate o f development , emi s s ions from an uncon­ trol l ed Wanke l engine compare wi th tho s e of an uncontr o l l ed p i s ton en­ g ine o f equivalent power approximately as fol lows : hydrocarbons 2 - 5 t imes higher , carbon monoxide 1 -3 times higher , and oxides o f nitrogen 2 5 - 75 percent l ower . The e f fect o f EGR on emi s sions from a Wankel engine wi thout a ca talys t or thermal reac tor i s shown in Tab le 3 - 6 . With pena l t i es in fuel economy and d riveab i l i ty , EGR can be quite e f fec tive in reduc ing NO emi s s ions . However , HC and CO emis s ions are high , and thes e can X b e reduc ed t o approach the 1 975 / 7 6 s tandard s only by u s ing external emi s s ion-cont rol devices . The sma l l eng ine s i ze provides an advantage in packaging the s e devices . Wi th i t s inherently high exhaus t t emperatures and i t s exhaus t por t s al l adj acent , the Wankel engine i s particular ly we ll sui ted t o emis s ion control b y a thermal reac tor . Current p roduc t i on rotary en­ gines on compact cars operated wi th rich c arbure tor set tings and ther­ mal reac tors have b een d eveloped to meet the 1 975 s t andard s wi th NO X leve l s o f about 1 gram per mi le . However , the fue l -economy penal ty compared wi th a current equiva l ent p i s ton engine i s about 30 percent . The u s e of EGR and richer carburetion with the therma l reac tor reduces - 50 - ... - Digitized byGoogle 

TABLE 3 -6 * E f fec t of EGR on Wankel Bare Engine NO Emis s i ons X Cond ition Emis s ions in grams /mile** Driveab U ity HC co NO ---x - - Ba s e l ine Eng ine 19 50 2.5 Product ion Driveab ility l imited VI EGR 19 50 1.4 Poor ..... Richer carburetor s e t t ing + EGR 20 65 0 . 75 A cceptab le Leaner carbure tor improved induction sys tem, EGR. 19 55 0. 3 Accept ab le 0 * Genera l Motor s Dat a a t low mileage , 2 75 0 lb car ;:::;: <iS " ** 1 9 75 CVS -CH te s t procedure i'i " CD Q. 0" '< C) 0 � � (\) 

NO -emi s s ion leve l s , but no t yet to 0 . 4 grams per mi l e with ad equate X driveab i l i ty . The fue l - economy pena l ty increases by a fur ther 5 percent . Tab le 3 - 7 l i s ts the bes t emi s s i on leve ls obt ained wi th therma l -reactor Wankel -engine sys t ems . S everal of the s e cars have met the leve l s o f the 1 9 7 5 stand ard s , and one has nearly met the 1 9 7 6 l evel s . Toyo Kogyo has d emonstrated d urab i l i ty o f the rich thermal -reac tor sys tem by t es t ing one c ar succ es s ful ly to 5 0 , 000 mi les , and wi th another s t i l l und er t e s t at 2 8 , 000 mi les . The emi s s i ons from the s e cars have remained be low the 1975 s tandard s , and work to achieve the 1 9 76 NO re- x quirement i s c ont inuing . The b e s t res ults achieved with oxidation cataly s t s and rotary eng ines are shown in Tab l e 3 - 8. Leve ls approaching the 1 9 7 5 s tandards for HC and CO have been achieved at low mi leage wi th a c ompac t car . Other control approaches wi th the Wanke l engine have b een l e s s extens ively d eveloped . A t leaner carburetor s e t t ings , oxidation cata­ lys t s have been shown to reduc e HC emis s ions at l ow mi leage in a compac t car to l eve l s about 5 0 perc ent above the 1 9 7 6 s t andard s , and CO to wel l b e l ow the s tandard . However , the durab i l i ty o f the rotary- engine sys ­ tems wi th cataly s t s has not been evaluated . EGR has been shown t o re­ duce NO l eve l s below 0 . 4 grams per mi le , but engine HC and CO emi s s i ons X were comparab le to uncontrol led p i s ton- engine l eve l s . 3.9 S trati fied -Charge Engines S trati f ied -charge spark-ignit ion engines are being developed to remove s ome of the per formance and emi s s ions limi tat ions of c onvent ional s park-igni t ion engines by c ontro l ling the air- fuel mixing and combust ion proce s s occurring inside the engine cylinder . The basic conc ept i s not new and was fir s t s ugges t ed in the ear ly 192 0 ' s . Two s trati fied - charge eng ine types have b een deve loped to the mul t i -cy l ind er engine s t age . - 52 - Digitized by Coogle 

TABLE 3- 7 Bes t Emis s ions Res u l ts . Thermal Reac tor and Wankel Engine 2 750- lb Compact Car * ** *** Manufac turer Sys tem Mi l eage No . of Tes ts Emis s ions in g/mile Fue l Penal ty HC - co - NO percent --x Toyo Kogyo Reac tor 4 , 000 Many 0 . 32 3.1 0 . 83 6.5 50 , 000 3 0 . 36 2.6 0 . 87 Reac tor + low 8 0 . 35 2.2 0 . 49 12 . 0 l.n EGR w Genera l Mo tors Reac tor low 72 0 . 60 5 .0 0 . 60 (bes t e f fort ) low 1 0 . 43 2.8 0 . 44 *All thes e sys tems are carbureted fuel rich (about 1 2 : 1 ) 0 <6" **19 7 5 CVS -CH tes t p rocedure ;::+ N. CD Q. rr ***Re la t ive to 1 9 7 3 produc t ion ro tary eng ine car '< C) 0 & ,...._ (\) 

TA BLE 3 - 8 Emi s s ions a t Low Mileage , Ro tary Engine with Ox idat ion C a t a lys t* Sys tem No . of te s t s Emi s s ions grams / mile** co HC !!!x Oxidat ion cataly s t 22 0. 7 0.4 1. 2 and a ir pump ( Be s t E f for t ) 1 0.4 0. 2 1.0 *General Mo tors data , 2750- lb car **1 9 7 5 CVS -CH te s t procedure - 54 - Digitized byGoogle 

3. 9. 1 Fue l - Injec ted S tratified-Charge Engine s Th is s tratified- charge eng ine concep t emp l oys a combinat ion o f a ir inl et port swirl and high- pres sure timed combu s t ion- chamber fuel inj e c t ion to achieve a local fue l - r ich igni table mixture near the po int of ignition wh ile the overa l l air- fuel ratio sup p l ied to the eng ine is fuel- lean for mo s t operat ing cond i t ions . Research and development on th is concep t , the open- chamber s trat i f ied- charge eng ine , has been sponsored by the U . S . Army Tank and Au tomot ive Command (TACOM) for a number of year s . This work has in­ vo lved deve l opment and tes t ing of two eng ine des igns , one based on the Ford Programmed Combu s t ion Proce s s ( PROCO) and the o ther based on the Texaco Combus t ion Pro ce s s ( TCP) . The pre s ent TACOM vehicles employ exhaus t-gas rec ircu l a t ion for NO control and oxidiz ing catalys ts for X contro l of carbon monoxide and particul ar ly unburned hydrocarbons . As a consequence , the usual probl ems with oxid iz ing cataly s t dur ab i l i ty have been exper ienced . The se eng ine s are four - cyl inder eng ine s nomi­ nal ly rated at 70 horsepower for the mi l itary j eep . Mil i tary vehicles equ ip ped with four- cyl inder L- 141 eng ine s modified by bo th Ford and Texaco are current ly undergo ing emi s s ions durab i l ity tes ts . Emi s s ions leve l s for the se veh ic l e s , wh ich are equipped with oxid i z ing cataly s t s and exhau s t- gas rec ircul a t ion , are pre s ented in Tab l e 3- 9 for the Ford and Texaco veh ic l e s . Re sul ts ind icate tha t wi th low vehic l e mileage the s e sy s tems are capable o f meeting the 1 9 7 6 federal emi s s ions s tandards . Durab il ity resul ts are al so pre s ented . The mo s t �por tant conc l u s ion from the durab il ity tes ts is tha t the bas ic combus t ion proc e s s is s table . Difficu l t ie s with p lug­ g ing of EGR sys tems with p art icul ates were exper ienced dur ing th i s mileage accumulation . The Ford eng ine required tw o cataly s t changes and frequent maintenanc e . The Texaco engine used three oxidat ion c a ta­ lys t s in s e r ie s to achieve the requ ired HC and CO emi s s ion contro l . Thes e eng ine s are s t i l l in the re search s tage and are no t produc tion - 55 - Digitized byGoogle 

TABLE 3- 9 Emi s s ions from Mil i tary Jeep wi th S trat i f ied- Charge Engines Engine Mi l eage Emiss ions grams /mi leb HC co NO -x L - 14 1 Ford low 0 . 37 0 . 93 0 . 33 PROCO 1 7 , 1 23c 0 . 64 0 . 46 0 . 38 L- 14 1 Texaco low 0 . 37 0 . 23 0 . 31 TC pd 10 , 000 o. 77 1 . 90 0 . 38 a Emis s ion contro ls inc lude ox idat ion catalys t , EGR , thro t t ling at light load . b l 9 7 5 CVS -CH tes t procedure . c Vehicle required two oxidation catalys t changes dur ing the 1 7 , 1 2 3 mi leage durab i l i ty tes t ing . d Three oxidat ion cata lys ts in s eries us ed to achieve low HC and CO emis s ions . - 56 - Digitized byGoogle 

prototypes . Durab i l i ty t e s t s with thes e vehi c les are continuing at the pre s ent t ime . In add i tion to work per formed under contrac t to TACOM , Ford has c onducted experiment s invo lving this type o f engine in pas s enger cars . Both four -cylinder and eight -cyl inder engine c onver s i ons have b een u s ed . In add i tion , s trati fi ed -charge engine ins tal lations have been made on two comme rcial - type vehic les . I t i s evident from Tab le 3 - 1 0 that s everal o f the vehi c les under tes t in this program are capab l e o f meeting the 1 9 7 6 federal emi s s ion s t andard s at low vehi c l e mi l eage . One o f the advantages o f the s t rati fied - charge engine i s exc e l ­ lent fue l economy relative to convent ional engines , par t icularly when emis s ions c ontro ls are app lied . The origina l vers ion of the s trat i fied ­ charge L - 14 1 engine develop ed for opt imum fue l economy showed a 3 0 per­ cent fue l economy gain over the c onventional c arbureted engine . However , as in a convent ional engine , when EGR i s used to reduc e NO emi s s ions , X the fuel economy i s reduc ed . With NO emi s s i ons at 0 . 33 grams per mi l e , X the emi s s ions -contro l led s trati f i ed -charge engine fuel economy i s com- parab l e to that of the origina l L - 14 1 convent i ona l engine . Wi th l e s s EGR , at 0 . 7 grams p e r mi l e N O , about a 10 percent fue l economy gain i s X obtained . 3.9.2 Carbureted S t rat i f i ed -Charge Engine An a l ternative approach , the CVCC system , now being deve l oped by Honda , achieves charge s trati fication wi th a prechamber and dual carburetor . The engine uses a convent ional engine b lock , pis tons , and spark p lugs ; only the cyl inder head , intake and exhaus t mani folds , and carb uretor are modi fied . The cyl inder head contains a sma l l pre­ combus t ion chamber in add i t ion to the main combus t i on chamb er . The spark p lug is located in the p rechamber , which is fed through a s epa­ rate carburetor and intake sys t em with a fuel -rich mixture through a sma l l th ird valve . The main carburet or and intake sys tem feeds a fuel ­ l ean mixture to the normal intake valve . - 57 - Digitized byGoogle 

Tab le 3 - 10 Low-Mi leage Emi s s ion Leve l s for PROCO Convers ion ( F i gure s are Aver age s for Number of Te s t s Shown) (A l l veh i c l e s use EGR and nob le me ta l ca t a l y s t s ) CVSLCH Te s t , CVS Fue l GramsLMi le Economy , Ine r t i a Te s t No . o f HC co NOx Mile s / Ga l lon We igh t , Pound s Te s t s -- PROCO 141 -C ID Capr i s 0 . 12 0 . 46 0 . 32 20 . 4 25 00 6 0 . 13 0 . 18 0 . 33 25 . 1 0 . 11 0 . 27 0. 32 22. 3 2 5 00 I VI 00 PROCO 35 1 - C ID Torino 0 . 30 0 . 37 0 . 37 14 . 4 45 00 5 I PROCO 35 1 -C ID Montegos 0 . 36 0 . 13 0 . 63 0 . 33 1 . 08 0 . 39 12 . 8 M- 15 1 PROCO \-Ton Truck 0 . 12 0 . 30 0 . 34 20 . 2 3000 4 \-Ton PROCO Ma i l Truck 0 . 18 0 . 21 0.51 22 . 9 25 00 9 0 <6" ;::+ N. CD Q. rr '< C) 0 & ,...._ (\) • 

The fue l -rich mixture ensures good ignition ; the approximately s toichiometric mixture at the prechamber exit propagate s the f lame into the fue l- lean mixture in the main chamber . A s low-burning flame i s required t o reduce NO formation and a l l ow HC and CO burnup ins ide the X engine . Emis s ions o f NO , CO , and HC are al l lower than tho se o f a con­ x ventional engine at the s ame lean air- fuel ratios . In F ebruary 1 97 1 , emi s s ions data wi th thi s system on engine dynamometer t e s t s indicated the engine could meet 1975 s t andard s ; the firs t succes s fu l car t e s t that met the standard s was in Spring 1 97 2 . In addi tion t o d eve loping a 2 - l i ter , 4 -cylinder engine for their own vehic l e , Honda has app lied the s ame t echniques t o mod i fy two Chevro let Vega 4 -cylinder engines . The Honda system i s the mo s t d eve loped s trat i fied -charge engine to date and has the lowes t bare-engine emi s s i ons . Low-mi leage emis s ions data are given in Tab le 3 - 1 1 for 54 Honda vehicles and two modi fied GM Vegas . Al l thes e cars met the 1975 s tandards without EGR or exhaus t treatment , and Honda has expres s ed confidenc e that l arger engines us ing the CVCC approach could also b e made to meet 1975 s tand ard s wi thout a cataly s t . Espec i a l ly impre s s ive is the s tandard devi at ion o f the low­ mi leage emi s s ions o f the s e vehi c les . The s tandard d eviation i s 10 to 15 percent o f the mean emi s s ions . In compar i s on , mas s -produc ed con­ ventional- engine vehicles show s tandard d eviations of 3 0 percent o f the mean at higher emi s s ion l eve l s . Three Honda cars have c omp leted 5 0 , 000-mi l e durab i l ity t es t ­ ing and met the 1975 s tandard s wi th eas e a t every 4 , 000 mi les . Data for these tes t s are given in Tab l e 3 - 12 . The Federal Tes t Procedure 11 - lap mode was fol lowed in these tes t s . Maintenance required was minor . In a recent series o f three tes ts at low mi leage , the average emis sions measured were 0 . 25 grams per mi l e HC , 2 . 5 grams per mi le CO , - 59 - Digitized byGoogle 

TABLE 3- 1 1 Low-Mi l e age Emi s s ions Da t a from Honda Tes t s o f CVCC Sys tem * Eng ine D i s p l a cement , Number o f Emi s s ions grams [mi l e Vehicle cub i c inche s Vehi c l e s HC co NO X Hond a C ivic with CVCC Manua l Transmis s ion 122 25 0 . 23 2 . 41 0 . 95 Hond a C ivic with CVCC A ut oma t ic Transmi s s ion 122 3 0 . 23 2 . 60 1 . 15 Hond a C ivic with Improved CVCC Manua l Transmi s s ion 122 25 0 . 21 2 . 33 0 . 75 Hond a C ivic wi t h 0\ 0 Fur ther Improvement s Manua l Transmi s s ion 122 1*** 0 . 25 2.5 0 . 43 Or ig ina l GM Vega Manua l Transmi s s ion 140 1 2 . 13 10 . 6 3 . 80 GM Vega with CVCC Manua l Transmi s s ion 140 1** 0 . 26 2.9 1 . 18 GM Vega with Improved CVCC Manua l Transmi s s ion 140 1** 0 . 26 2 . 62 1 . 16 0 <6" ;::+ N. CD Q. rr '< * 1 9 75 CV S -CH t e s t procedur e C) ** Two - t e s t average 0 *** Avera ge o f three t e s t s & ,...._ Da t a for t h i s t a b l e current on November 24 , 1972 (\) 

TABLE 3 - 1 2 Durab i l i ty Data from Honda T e s t s o f CVCC Sys t em Emi s s i ons 1 D e teriorat i on Factor * Vehi c l e No . Miles HC co NO HC co NO X X 1006 4 , 000 0 . 22 2.4 0 . 96 1 . 16 1 . 07 1 . 03 5 0 , 000 0 . 26 2.6 0 . 99 2033 4 , 000 0.21 2.7 0 . 95 ** 5 0 , 000 Ex trap o l a t ed 0 . 25 2.7 0 . 90 1 . 15 1 . 08 1 . 04 5 0 , 000 Actual 0.21 2.2 0 . 93 2034 4 , 0 00 0 . 25 2.5 0 . 89 ** 5 0 , 000 Extrap o l a t ed 0 . 25 2.6 0 . 82 1 . 06 1 . 05 0 . 98 5 0 , 000 Ac tual 0 . 22 2.2 0 . 70 2 0 35 4 , 00 0 0.21 2.4 0 . 95 0\ t-' ** 5 0 , 0 00 Extrapo l a ted 0 . 24 2.7 0 . 96 1 . 12 1 . 12 1 . 00 3 6 , 000 Ac tual 0 . 19 2.2 0 . 80 - * Mi l eage accumu l a t ion for vehic l e No . 1 0 06 was ob t ained on a chas s i s dynamomet er . 0 The other three veh i c les were run on a p roving ground . <6" ;::+ N. CD ** Q. Vehi c l e s 2 0 3 3 , 2034 , and 2035 were mod i f i ed to an improved ver s ion b e fore the rr '< 5 0 , 000 -mi l e t es t ing was comp le t ed . Thu s , to c a l c u l ate d e terioration factors , C) emi s s ion values at 5 0 , 000 mi les were extrap o l a t ed from preced ing mea surement s . 0 & ,...._ Data for thi s tab l e were current on November 24 , 1972 . (\) 

and 0 . 43 grams p er mi l e NO • Thes e l evel s were achi eved by improving X the configurat ion o f the auxi l iary combus t ion chamb er and the air - fuel control p a t t ern . No EGR or exhaus t - treacment d evices were us ed . The emis s ions are not e s p ecial ly s ens i t ive t o variations in air­ fuel rat io . Thus the required p er formanc e o f the doub l e carburetor sys ­ tem is no more demand ing than current requirements . The two throt t l e p lates are l inked mechanic a l ly . The mean air- fuel rat io varies with op erat ing mode . The new cyl ind er head i s about the s ame height as a conventional head . The new h ead , intake , and carburetor on the modi fi ed Vega f i t comfortab ly into t h e engine comparcment . T h e engine can op erate on regular l eaded gaso l ine ; durab i l ity t e s t ing has been on unl eaded gaso­ l ine to s imulate fuel antic ipated in the Uni t ed S t ates in 1 9 7 5 . The effec t s on vehic l e p er formanc e o f the CVCC sys tem are smal l . There i s a s li ght los s in power for the same engine d i sp lac ement due to leaner op eration and d ecrea s ed vo lumetric e f ficiency . Fuel economy i s es s ent ial ly unchanged . There are no driveab i l i ty p enalties . D eve lopment o f the Hond a CVCC engine to achi eve l ower NO emis ­ x s i ons i s cont inuing . The e ffect s o f EGR and modi fications to the basic combust ion proc e s s are being examined . 3 . 10 E f fec t o f Emi s s ion-Control D evices on Ve�ic l e Per formanc e , Driveab i l i ty. Fuel Economy. and Safety S ome of the emis s ion-contro l d evi c es and techniques required to meet the 1 9 7 6 emi s s ion s tandard s have a profound e f f ec t on at l ea s t three areas o f vehic l e p er formanc e : ac cel eration capab i l i ty , fuel economy , and driveab i l i ty . There i s a l s o s ome concern that poor per­ formanc e of such cars wi l l make them unsafe in c ertain circums tances , for examp l e , i f the vehic l e s tal l s when acc e l erating into fas t -moving - 62 - Digitized byGoogle 

traffic . The cus tomer i s s ens i t ive to the s e charac teri s t i c s which affec t both his pocketbook and his atti tude toward any particular vehic l e . Tradi tional ly thi s area has b een one in whi ch customer comp l aint s and warranty returns have been espec i a l ly preval ent . I t is therefore not surpri s ing that manufacturers have reg i s tered great con­ cern i n the pas t about the adverse effect s of emis s ion c ontro l d evices . By the s ame token , however , the market p lac e impo s es considerab l e in­ herent mot ivat ion for manufac turers to d evo t e great attent ion to pro­ duct improvement in thes e areas . The comment s that fol l ow in this s ec tion refer primari ly t o vehic l e s equipped wi th t h e dual -cataly s t emi s sion-c ontro l sy s t em . I n general , vehic l e acce lerat ion c apab i l i ty i s reduced by contro l meas ures appl i ed for contro l o f a l l three po l lutant s (HC , CO , and NO ) ; however , NO contro l measures which reduce c ombus tion tem- x X perature have the mos t s erious del eterious effec t s . Reductions in compres s ion ratio to enab l e u s e o f lower -oc tane gas o l ine resu lted in accel eration penal t i es , as did the minimization o f enrichment tech­ niques formerly provided s peci fical ly for rapid acceleration capab i l ­ ity . In add i tion , the u s e o f EGR to reduce combus tion temperatures and thereby inhib i t NO production impos es a s evere acceleration X pena l ty . Los s e s in fuel economy accompany mos t o f the s e l o s s e s in ac ­ celeration capab i l i ty and are aggravated by countermeas ures taken t o overcome defici encies in acc eleration capab i l i ty and driveab i l i ty . Many o f the smal ler engines have been dropped in the various car l ines . The u s e o f a larger d i s p lacement engine re s u l t s in a fuel economy pen­ a l ty for b oth c i ty and open-highway d riving . When EGR is us ed to con­ tro l NOx emi s s ions , the mixture mus t be enriched to retain ad equate driveab i l i ty , caus ing d ras tic reduc tions in fuel economy . - 63 - Digitized byGoogle 

The mo s t troub l esome of numerous driveab i l i ty p rob lems i s the cold - s tart prob l em . The quick choke ac t ion and sub s equent lean mixtures required to minimi z e HC and CO emis s ions introduce p rob l ems wi th engine s ta l l s and uns ati s fac tory drive - away d uring warm- up . EGR and spark re tard caus e such prob lems as lack of response , d i e-out s , and hes i tat ion on accel eration . In i t s January 1 , 1 9 7 2 , report , the CMVE conc lud ed that a l l three areas o f vehic l e per formanc e d i scus s ed above would b e advers ely af fec t ed by the 1 9 7 5 emis s ion-control sys tems . Information received from manufac turers ind i c ated los s e s in acceleration cap ab i l ity rang ­ ing from a minimum o f 5 p ercent to a maximum of 20 p erc ent over 1 97 1 level s . Al l manufac turers ant ic ipated los s e s in driveab i l i ty , in s ome cases indicated to b e s evere . Antic ipated increases in fuel c onsump ­ tion ranged from 5 to 15 perc ent f o r s tand ard sized cars u p to 20 to 30 percent for smal l cars , again over 1 9 7 1 level s . Much of the dete­ rioration in per formance was ant icipat ed to come with the introduct ion o f NO requirements in 1 9 7 3 , and early reports on per formanc e o f the X new mod e l s have confirmed thi s . During 1 9 7 2 , the CMVE has received reports on both the 1975 and 1976 emi s s i on-contro l sys tem progres s . Whi l e manufac turers are s t i l l conc erned wi th p erformanc e , par t icular ly fuel cons ump t i on , the concern over vehic l e driveab i l i ty has d imini shed . No sub s t antial new ac celeration , fuel economy , or driveab i l i ty prob l ems are introduced wi th the 1 9 7 6 emis s ion-contro l sys tems com­ pared wi th the 1 9 7 5 sys tems . At the same time , cons iderab l e p rogres s has been made in finding s olut i ons t o prob lems that appeared t o b e very s er ious one year ago . It seems l ike ly that comp e t i t ive pre s ­ s ures wi l l result i n furth er imp rovement s and improved reliab i l i ty in thes e per formanc e areas . The effo rt r equired i s e s s ent ial ly engi ­ neering d evelopment based on ext ens ive fi eld experienc e wi th th es e new sys tems . The maj or long - t erm c onc ern should be the continuing fuel - 64 - Digitized byGoogle 

economy penal ty which resul t s from the decreas ed compres s ion ratio to a l low the use o f unleaded fuel s , compounded by the use of EGR to con­ trol NO emi s s ions to very low level s , and aggravated by the increas ed X engine s i z e s introduc ed to comp ensate for the lo s s in per formanc e . 3 . 11 Al ternative Fue l s On e approach t o reduce emis s ions from conventional engines i s the u s e o f alternative fuel s . The u s e of lique fied natural gas (LNG ) , l iquefied p etro l eum gas (LPG) , hydrogen , and alcoho l s have b een con­ s id ered by the Commi t t ee . 3 . 11 . 1 Liquefied Natural Gas and Liquefied Petro l eum Gas B o th industry and governmental group s have evaluated natural gas and propane (LPG) to determine their capab i l i ty in reducing emi s ­ s ions from automobi les . One engine manufac turer showed that emis s ion leve l s approaching the 1975 - 7 6 s tandard s can be achieved , but exhaus t gas rec irculation i s s ti l l required t o reduc e NO formation t o the X 1975 - 7 6 s tandard . There i s an 8 perc ent lo s s in peak engine power ( 35 0 c u . in . 19 70 eng ine ) from ga s o l ine when us ing LPG and a 15 percent los s us ing na tura l gas . There is a s ub s tant i a l los s in fuel economy { 30 p ercent ) , and dr iveab il i ty is imp a ired . The us e o f LPG for s t ar t ­ ing and warm-up i n a dua l - fue l c a r u s ing gasol ine for convent iona l operation was attemp ted . Cold - s tart emi s s ions are d ecreased . On an experimental natural -gas 6 - cyl ind er engine s i z ed for bus operation , another manufac turer showed that the use of compres s ed or l iquefied natural gas would produc e emis s ions which wou ld meet 1 975 s tandard s .The 1976 NO stand ard c ould b e met only with EGR , a cata- x lytic a fter-burner , and a great reduc t ion in performance . Th e emi s - sions were odor l e s s and there was n o particulat e mat t er present . - 65 - Digitized by Coogle 

There are over 5 , 000 cars converted to run on gas eous fue l s in the Lo s Angeles bas in where gas supp l ie s and l iquid sy s tems have been j o ined toge ther to provide the ga s eous fue l s to the c ar opera tors . Emis s ions are c leaner , maintenance is reduced , but a heavy bulky tank is requ ired to ho ld the gaseous fue l . 3. 11. 2 S ta tus of Lique fied-Gas Subs t itutes for Gas o l ine The CMVE has inve s t iga ted the technical probl ems and economic factors invo lved in supplying natura l gas and LPG . It is po s s ib l e to mod i fy the pe tro leum re fining proces s so that LPG can be s ub s t i tu ted for gas o l ine for mo tor vehic les . The orig ina l cap ital c o s ts wou ld be in the $ 50 b il l ion range . The fue l co s ts to the cus tomer wou l d be about twice as much as gas o l ine present ly c o s ts . A l s o , there is a s e r ious ne t l o s s o f energy in chang ing from gasol ine to LPG . The percentage of crude o i l consumed in the p roce s s ing opera t ions wou ld increase from about 4 percent to about 14 percent . Th is would be an unre coverable was te o f na tural resources . There i s not enough LPG , LNG , or Synthe tic Natural Gas ( SNG) current ly availab l e to be s igni f ic ant i f convers ion were des ired now . A three-year lead- time for making changes for supply ing the se al terna­ t ive fue l s is a minimum . 3. 11. 3 Hydrogen Hydrogen gas has three p roper ties wh ich , when taken toge ther , give it a unique po tent ial as a vehicular fuel . F ir s t , s inc e there is no carbon in the fue l , the problems of unburned hydrocarbons and of carbon monoxide do no t exis t . No a f ter-burner , c a talys t , or other se condary reac t ion ve s s e l s are needed . Second , the f l ammab i l ity l imits o f hydrogen are extreme ly wide . The vo l ume percentage of hydrogen in a ir c an r ange over a fac tor o f 1 9 - 66 - Digitized by Coogle 

and s t i l l be ignited by a s p ark . Th is contr a s t s with the fac tor o f 5 for gasol ine vapor . Because o f this high f l ammabi l ity range , very l e an mixtures o f hydrogen gas may be used , thereby insuring that NO wil l X s tay with in accep table s tandards . With hydrogen as a fue l , no EGR is needed to reduce NO • X Third , the supp ly of hydrogen gas is vir tual ly ine xhaus t ib le , a l though p l ants for i t s ma s s produc t ion are no t yet ava i lab le . Cur­ rently , the cheape s t way o f making hydrogen gas is to use natur a l gas as a base mater ial . When natural gas approache s exhaus t ion , the cheapes t way o f making hydrogen gas wil l be to use c o a l as the base mater ial . When the price o f coal become s too h igh , hydrogen can be made by hea t ing or elec tro lyz ing water . A source o f energy is required to produce hydrogen by any o f these me thod s . An eng ine burning hydrogen g as a t s to ichiome tr ic ra tio emi ts no measurab l e hydrocarbons , organic or sul fur compounds , and only one­ tenth the NO as when burning gasol ine vapor at its s toichiome tr ic X r a t io . Fur thermo re , at an air-fue l r a t io o f 1 . 75 times s to ich iome tr ic , the NO compo s i t ion o f the hydrogen exhaus t is reduced by a fur ther X fac tor of 20 , we l l be l ow the 1 9 76 s t andards . Several exper imenters have repor ted s a t is fac tory performance from internal combus t ion eng ine s conver ted to hydrogen fue l . The cryogenic fue l tank p lus i t s hydrogen fue l would we igh 40 percent les s than the conventiona l tank p l u s i t s gas o l ine having the s ame cruis ing rad iu s , but would occupy five time s the vo lume . O ther s torage me thods are be ing sough t . One company i s a t temp t ing to produce H and co from unleaded 2 2 g a s o l ine in the car gas tank u s ing a smal l reformer loc a ted in the trunk o f the car . The H and co , produced in small quanti ties to 2 2 avo id safe ty probl ems , could be burned c le anly in the s l ight ly modified - 67 - Digitized byGoogle 

O t to-cyc l e eng ine . Q ue s t ions remain on the ab i l i ty o f the reformer to c arry ou t thi s reac t ion and on its e f f ic iency , s ize and c os t . Sound exper imental work and soc io-economic impac t s tudies on the use o f hydro­ gen as a veh icu l ar fuel are requ ired be fore unqu a l i f ied succes s could be c l aimed for the approach . In any c a s e l arge- s c a l e use o f hydrogen as an au tomo t ive fuel is no t pos s ib l e by 1 9 76 . 3. 11 . 4 Alcoho l s Alcohol has been proposed and used as a fuel for the interna l­ combus tion eng ine ; e . g . , me thyl alcoho l is wide ly used as a r ac ing fue l . Me thano l has the advantage of provid ing a lower combus t ion tempera ture , reduc ing the NO emi s s ions , and i t a l s o has lower l ean mis f ire l imi ts X than gasol ine , thu s reduc ing HC , CO , and NO emi s s ions wh ile ma intain- x ing a s a t i s fac tory dr iveab il ity . Emi s s ions te s t s have been run on a 1 9 7 0 American Mo tors Greml in , us ing pure me thano l a s fue l , with a plat inum cataly s t conver ter in the exhaus t . Emi s s ions o f HC , CO , and NO ' u s ing the 1 9 7 2 CVS Federal Te s t Procedure , were b e l ow the 1 9 7 6 x s tandards . Me thano l has a lower heat ing value th an gaso l ine , so y ields correspond ing ly fewer mi les per gal lon . S tar ting a t low temperatures with me thano l is a problem ; vo l a t i l e compounds have to be added to a s s ure smooth s tar t ing . S imilar data on ethano l are no t ava i l able . Te s ts on gas o l ine wi th up to 30 percent e th anol as fuel show no s ubs tantial improvement in emi s s ions over pure gas o l ine . - 68 - Digitized byGoogle