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# OAR Box 1830 Prepped by Ollie Stewart



### Document

Number: 

# 14 ) IV-B-1 0 Docket Number: 

# A-87-1 1

Printed 11/13/2008 7:20:51 AM Sheet 14 of 232P. 2

P UNITED STATE S ENVIRONMENTA L PROTECTION AGENC Y WASHINGTON

, D.C . 20460 

### SE P 

### - 8 198

8

OFFIC E O F AI RAN D RADIATIO N MEMORANDU

M SUBJECT : FROM : TO : VO C Runnin g Losse s fro

mMoto r Vehicle s Richard D . Wilson , Offic e o f Mobil e Sou r Ai r Managemen t Divisio n Director s Region s 1 , 3 , 5 , 9 Ai r an d Wast e Managemen t Divisio n Directo r Region s 2 Ai r an d Toxic s Divisio n Director s Region s 7 , 8 , 1 0 Air , Pesticides , an d Toxic s Managemen t Divisio n Directors , Region s 4 , 6 Recentl ythe subjec t o f VO C runnin g losse s an

d evaporativ e emission s fro

mmoto r vehicle s ha s receive d a lo t o f publi c attention . Th e purpos e o f thi s memo i s t o provid e yo u wit h som e informatio n whic h yo u an d your staf f can us e in responding t o question s fro

m Stat e an

d loca l officials , th e press , o r others . Backgroun

d o n Evaporativ e Emission s "Runnin g losses " ar e emission s o f VO C release d fro mpoint s othe r than the tailpip e o r crankcase , whil e an engin e i s running . The yar e distinguishe d fro m "evaporativ e emissions, " whic h ar e thos e VO C losse s tha t occur whe n the engin e i s turne d off . Evaporativ e emission s have bee n regulate d i n stage s o f increasin

g stringencysinc e 1971 . The curren t standard s fo r evaporativ e emission s represen t a contro l leve l o f abou t 95 % fro muncontrolled . Theyhave bee n in effec t sinc e 198 1 fo r light-dut ygasolin e car s an d truck s an

d sinc e 198 5 for heavy-dut ygasolin e truck s an d buses .P. 3

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- A s yo u know , a fewyear s ag o EPAdetermine d tha t th e hig h volatilit yo f commercia l gasolin e wa s causing vehicle s in-us e t o excee d thei r certificatio n standard . I n Augus t 1987 , EP A propose d t o restric t gasolin e volatility . W e expec t a fina l rul e in 1989 . W e have als o foun d a numbe r o f early-1980' s model s tha t have needed t o be recalle d for noncomplianc e wit h the evaporativ e emission s standard eve n whe n teste d o n the les s volatil e certificatio n fuel . Suc h noncomplianc e wa s no t surprising , give n the stringenc yo f th e 198 1 standard . Recall s t o correc t thes e problem s ar e underwa yan d we believ e manufacturer s ar e doin g a bette r jo b o n thei r newe r models . Ove r the las t coupl e o f year s we have als o realize d tha t evaporativ e emission s ar e greate r a t highe r ambien t temperature s than a t the temperature s tha t ar e use d fo r certificatio n testing . Th e sensitivit yo f evaporativ e emission s t o temperatur e i s greate r o n current , highl yvolatil e commercia l gasolin e than o n certificatio n fuel . Fo r severa l practica l reason s we have no t propose d t o us e highe r temperature s i n certificatio n testing . However , les s volatil e commercia l fue l woul d greatl yreduc e th e exces s emission s attributabl e t o hig h temperature s i n the rea l world . Also , w e hav e bee n expecting tha t mos t vehicle s meeting EPA' s propose d standard for on-boar d refueling emissio n control s woul d hav e integrate d evaporative/refueling contro l system s tha t woul d contro l evaporativ e emission s eve n a t temperature s abov e the officia l tes t temperatur e range . Running Losse s Running losse s ar e nearl yal l du e t o evaporatio n (an d i n extreme cases , boiling ) o f fue l fro mthe fue l tank . Whe n a vehicl e i s running , it s fue l tan k temperatur e tend s t o ris e t o abou t 15-25° F above th e ambien t ai r temperature . Thi s heating occur s becaus e o f the ho t ai r flowfro mthe engin e compartmen t dow n unde r the vehicle , fro mthe proximit yo f th e ho t exhaust , fro mho t pavement , an d fro mhea t generate d i n th e rea r axl e bearing s an

d gears . O n fue l injecte d cars , fue l i s constantl y circulate d fro

mthe fue l tan

k t o the engin e compartmen t an d back , an

d the returnin

g fue l carrie s significan t hea t bac k t o the tank . U.S . vehicle s ar e designe d s o tha t an yvapo r generate d i n th e fue l tan k i s carrie d b

ya hos e t o the engine , wher e i t i s inducte d an d burned . Whe n the engin e i s off , thi s sam e hos e carrie s vapor s t o th e carbo n caniste r for storage . Th e variou s hose s an d valve s ar e arrange d s o tha t a singl e vacuu mline t o the engin e draw s vapo r fro mth e fue l tan

k an d purge s th e caniste r wit h fres h air . Officially , runnin g losse s wit h standar d tes t fue l a t standard tes t temperature s during the standard 2 0 minut e driving cycl e mus t be counte d agains t the evaporativ e emission s standard . However , unde r thes e condition s runnin g losse s ar e believe d t o be virtuall yzer o o n ne wvehicles . Consequently , i n practic e runnin g losse s ar e no t measure d o n certificatio n prototypes .P. 4

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- Wit h hig

h volatilit yfuel s an d high ambien t temperatures , a faste r vapo r flowcan b e generate d i n the fue l tan k tha n i s inducte d int o the engin e through the purg e line . The exces s flowi n the vapo r line enter s the carbo n canister . Onc e the carbo n i s saturate d wit h vapor , the exces s flo wi s release d t o the atmosphere . I t i s als o commo n unde r thes e condition s fo r fue l tan

k pressur e t o increas e s o muc h (sinc e a flo wrestricto r i n the vapo r hos e t o the engin e create s a bac k pressure ) tha t venting occur s a t th e fille r cap . A s a safet ymeasure , fille r cap s ar e designe d t o releas e an ypressur e i n the fue l tan k greate r than abou t 0. 5 t o 2 ps i above atmosphere . Vehicle s var

yi n thei r design rat e o f purg e flowint o the engine , an

d i n howquickl yfue l i n the tan k heat s up . I n additio n t o ambien t temperature , clou d cover , an

d win d speed , the driving patter n affect s the rat e o f temperatur e ris e i n the tank , a t leas t o n shor t trips . Driving patter n affect s ai r flowunde r the vehicle , fue l recirculation , axl e bearing hea t rejection , hea t rejectio n fro mthe engine , an

d exhaus t pip e an

d muffle r surfac e temperatures . Th e resul t i s tha t vehicles ' runnin g losse s a t an

yinstan t depen

d o n the vehicl e geometry , tri p speed , tri p history , fue l volatility , initia l fue l tan k temperatur e (i f highe r than ambien t du e t o a previou s tri p o r t o sola r warming) , an d ambien t temperature . Th e runnin

g los s valu e o f 9 gram/mil e whic h yo u ma yhav e heard abou t or see n in the trad e pres s i s a n averag e fo r the firs t five vehicle s we tested . I t applie d onl yfo r the combine d extreme s o f tri p lengt h (6 0 minutes) , temperatur e (95°F) , an

d volatilit y(Reid Vapo r Pressur e o f 11. 5 pound s pe r squar e inch) . Severa l mor e recentl yteste d vehicle s hav e had lowe r averag e runnin g losses . Fo r comparison , the exhaus t H C standar d i s 0.4 1 gram/mil e an d a ca r jus t meeting the evaporativ e HC standard woul d emi t the equivalen t o f abou t 0.1 3 gram/mile . T o date , th

e Offic e o f Mobil e Source s ha s teste d abou t 1 0 lat e mode l vehicle s for runnin g losses , mos t o f the m a t 6 combination s o f temperatur e an d fue l volatility . W e ar e planning t o tes t a fewolde r vehicle s an d som e light-dut y truck s ove r the remainde r o f thi s fisca l year . W e als o pla n t o tes t som

e car s wit h differen t driving cycles . Th e firs t quarte r o f F Y 198 9 wil l b e devote d t o dat a analysis , prio r t o releas e o f MOBILE 4 in Januaryor February . Th e larg e variabilit yi

n tes t result s fro mvehicl e t o vehicl e wil l caus e a large r uncertaint yin the MOBILE 4 estimate s than we woul d like , bu t we se e n

o wa you t o f thi s predicament .P. 5

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- Implication s fo r SIP' s Th e effec t o f includin g runnin

g losse s i n M0BILE 4 wi n be t o increas e bas e yea r VO C inventories . However , w e ar e proceeding t o a fina l rul e o n reducing fue l volatility , t o whic h runnin

g losse s ar e ver

ysensitive . I f the propose d RV P limit s ar e adopte d in the fina l rule , runnin g losse s wil l b

e controlle d b

yabou t 8 0 t o 8 5 percent . Thi s woul d greatl y reduc e the impac t o f runnin g losse s fo r inventor yyear s afte r the effectiv e dat e o f the RV P reduction . Thi s dat e i s expecte d t o be befor e the attainmen t dat e target s i n EPA' s propose d post-198 7 polic yan d in the variou s bill s befor e Congress . Subsequen t phase-i n o f the additiona l reductio n fro mvehicle s equippe d wit h bette r contro l system s wil l assis t maintenance . Whil e the directio n o f the impac t o n bas e yea r VO C inventorie s i s clear , it s siz e i s not . Running losse s a s high a s the 9 gram/mil e cite d earlie r occu r onl yo n lon g trip s a t ver yhigh temperatures , e.g. , 95°F . I t wil l tak e mor e wor k t o develo p method s fo r Stat e an d loca l planner s t o estimat e the valu e o f runnin

g losse s for thei r loca l ozon e situation . I t may b e tha t runnin

g losse s ar e i n man ycase s no t ver

yimportan t t o peak ozon e level s becaus e loca l trave l pattern s ar e suc h tha t mos t runnin

g losse s occur to o lat e i n the da yt o reac t fully . Running losse s coul d be mor e importan t i n multipl e da yepisode s an d precurso r transpor t situations . Ther e ha s bee n som e speculatio n tha t running losse s ar e the "missin

g inventory " tha t account s for lac k o f progres s t o dat e o n ozon e reduction s and/o r contradiction s betwee n the inventor

yrati o o f H C t o NO x an d the ambien t ratio . Suc h speculatio n i s prematur e an d certainl yi s n

o basi s fo r relaxing effort s t o improve othe r part s o f the VO C inventory . Also , whil e running losse s ma ywel l be a significan t portio n o f a n area' s VO C inventor yon a ho t day , the yma ybe ver

ymuc h les s importan t o n coole r ozon e violatio n days . I a mno t attaching an ytes t dat a sinc e th e tes t result s t o dat e woul d b e mor e a sourc e o f confusio n than enlightenmen t an d becaus e w e ar e adding vehicle s t o th e dat a bas e eac h week . However , i f ther e i s an yothe r wa

yw e ca n be o f assistanc e t o you r offic e i n thi s are a betwee n nowan d whe n MOBILE 4 i s read y fo r release , pleas e le t me or Charle s Gra yi n An n Arbo r know .

cc : Geral d Emiso n Do n Cla y