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# OAR Box 1830 Prepped by Ollie Stewart



### Document

Number: 

# 37 ) IV-C-3
Docket Number: 

# A-87-1 1

Printed 11/13/20087:20:52 AM Sheet 3 7 of 232\ UNITE D STATE S ENVIRONMENTA L PROTECTIO N AGENC Y P. 2 

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Z Tj L - c-0 3 

### 3 AN N ARBOR . MICHIGA N 4810 5

OFFIC E O F A R AN D RADIATIO N 

# £ Samue l A . Leonard , Director Automotiv e Emissio n contro l Genera l Motor s Technica l Center 3040 0 Moun

d Roa d Warren , Michiga

n48090-901 5 Dea r Mr . Leonard : I woul d lik e t o than k yo u fo r you r Jun e 16 , 198 7 lette r relaying furthe r detail s o f Genera l Motors ' positio n o n the effect s o f onboar d refueling emissio n contro l system s o n increase s i n vehicl e weight , vehicl e lifetime fue l consumption , an d the ne t cos t o f onboar d controls
. EP Ai s alway s receptiv e t o manufacturers ' comment s o n it s regulatoryaction s an d encourage s suc h interactions
. Your comment s wil l b e considere d along wit h an

yother s we receiv e on thi s topi c a s w e formulat e ou r fina l rulemakin g action
. Th e ke ydifference s betwee n G M an d EPAcontinu e t o b e i n the area s o f the weigh t compounding effect , the adjustmen t fo r acceleratio n performance , an d the incrementa l weigh t o f onboar d vapo r recover

ysystems . The weigh t compoundin g effec t an d acceleratio n performanc e adjustmen t definitel ydo no t affec t curren t model s in whic h the onboar d systemi s retrofitte d o n the vehicle
. I n thi s situation , no structura l change s woul d b e expecte d t o be mad e t o accommodat e the new hardware
. Fo r ne w vehicl e models , EP Astil l question s whethe r the weigh t compounding effec t an d acceleratio n performanc e adjustment s ar e appropriat e fo r onboard
. Thi s i s becaus e o f the ver ysmal l weigh t increas e du e t o onboar d systems , whic h EP Abelieve s i s wel l withi n th

e rang e o f suc h thing s a s norma l design toleranc e an d vehicl e t o vehicl e weigh t variability
. However , w e wil l conside r thes e issue s furthe r in the cours e o f ou r onboar d refueling emissio n contro l rulemaking
. Finally , in you r lette r yo u hav e indicate d tha t Genera l Motors ' estimat e o f a n additiona l 7 pound s fo r a n onboar d refueling emissio n contro l systemi s indee d the incrementa l weigh t gai n whic h yo u anticipat e compare d t o curren t evaporativ e systems . EPA' s estimate , base d on a n in-dept h analysi s o f componen t weights , i s 4. 9 pounds
. W e believ e thi s estimate , whic h i s simila r t o value s supplie d b ymanufacturer s othe r than GM , i s an accurat e one . Therefore , w e canno t accep t the 7 poun

d valu e whic h yo u suggest .P. 3

«V r 5

Than

k yo u agai nfo

r you r letter . A s alway s EPA i s ope nt o an y ne w informatio nGenera l Motor s may hav e regardin g thes e issue s an

d woul d appreciat e receivin g furthe r comment s durin g the publi c commen t perio d o n our onboar d proposal . We wil l full y conside r the G

M comment s inour ongoin g deliberatio non refuelin g emission s controls . Sincerel y

yours ,

Richar d D . Wilso n Director , Offic e o f Mobil e source s
cc : Publi c Docke t #A-87-l l