EPA-420-S-76-101
Issue Paper
Cost effectiveness of a 2.0 g/test SHED
Evaporative Standard for Light Duty
Vehicles and Trucks
June 1976
Michael W. Leiferman
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Source Mobile Air Pollution Control
Office of Air and Waste Management
U.S. Environmental Protection Agency

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Cost Effectiveness of a 2.0 g/test SHED Evaporative Standard for Light
Duty Vehicles and Trucks
1.	Statement of the Problem
What is the cost effectiveness of reducing light duty vehicle SHED
evaporative emissions from a level of 6.0 g/test to 2.0 g/test?
2.	Facts Bearing on the Problem
a.	Exxon Research and Engineering Company conducted an evapora-
tive test program under EPA Contract No. 68-03-2172 . In this study,
six production vehicles which represented the four major U.S. manu-
facturers and two foreign manufacturers, were modifed in order to reduce
evaporative emissions. Costs for the required modifications were then
estimated. The resulting manufacturers' sales weighted retail price
increase to achieve an evaporative level of less than 6 g/test on each
vehicle was $2 per vehicle. The sales weighted retail price increase to
achieve an evaporative level of less than 2.0 g/test on each vehicle was
$3 per vehicle.
b.	Automotive manufacturers have supplied evaporative emissions
data on vehicles equipped with experimental control systems. Some of
the vehicle test data submitted by GM, Ford and Chrysler were less than
2.0 g/test. The increase in vehicle retail price for these modifica-
tions was estimated based on Exxon's Contract No. 68-03-2172 cost estimates.
From this information, the calculated sales weighted retail price in-
crease (over 1976 production vehicles) to achieve the 2.0 g/test level
was $7 per vehicle.
c.	For the twenty production vehicles tested for evaporative
emissions under Contract No. 68-03-2172, 83% of the emissions occurred
during the hot-soak test and 17% during the diurnal test. For the six
vehicJes modified to an evaporative level of less than 2.0 g/test, 59%
of the emissions occurred during the hot-soak and 41% during the diurnal.
3.	Discussion
a. In the Exxon program, the vehicles which were eventually
modified were also tested for evaporative emissions in their production
configuration. In production form all six vehicles had evaporative
emissions greater than 6.0 g/test. On most of these vehicles several
different modifications were made during the test program. At some
point in the program, the evaporative emissions from each vehicle de-
creased from a value above 6.0 g/test to a value of below 6.0 g/test.
Based on the cost of these modifications, the retail increase required
to achieve the 6.0 g/test level was estimated. As explained in reference
(1), the estimated vehicle retail price increase for a certain modification
^ ^Clarke, P. J., "Investigation and Assessment of Light Duty Vehicle
Evaporative Emission Sources and Control," Exxon Research and Engineer-
ing, EPA Contract // 68-03-2172, June 1976.

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-2-
is assumed to be twice the cost to the manufacturer of that modifica-
tion. The modifications performed on each vehicle and the estimated
price increase are listed in Table I. As shown, the estimated retail
price increase of the modifications ranged from $1.10,to $5.70. The
resulting manufacturers' sales weighted average is $2
After final modification, each of the six vehicles in the Exxon
program had an evaporative emission level of less than 2.0 g/test. The
retail price increase estimate was made and these are contained in Table
II. As shown the retail price increase estimates ranged from $2.00
on the Ford to $25.20 on the Mazda. The cost on the Mazda consisted mainly
of the underhood ventilating fan cost. Also worth mention is the fact
that the costs for the Pontiac are those associated with the Vega can-
ister system, not the ventilating fan system which was also tested.
On a manufacturer's sales weighted basis, the retail price increase
to reduce evaporative emissions from the current production level to the
2.0 g/test level is $3 per vehicle. This value was calculated similarly
to the 6.0 g/test cost as previously discussed. A detailed listing of the
modifications and corresponding emission levels for each vehicle are
contained in Attachments A-I through A-VI of Appendix A. Attachment VII
of Appendix A summarizes the initial and final emission levels for the
six vehicles.
b. Attachment B-I of Appendix B lists test results and information
on ten experimental vehicles which have given SHED evaporative test
results of less than 2.0 g/test. These vehicles were prepared and tested
by their respective manufacturers. Data on the GM and Ford vehicles
were supplied in response to California and Federal proposed evaporative
regulations, and the Chrysler data was contained in Chrysler's, "Progress
Report on Chrysler's Efforts to Meet the 1977 and 1978 Federal Emission
Standards for HC, CO and NOx" (Dec. 1975). Using this information,
along with the equipment cost information in Exxon's work under Contract
No. 68-03-2172, the estimated vehicle retail price increase for the
modifications on the vehicles listed in Table B-I has been calculated.
This information is contained in Table III. As shown the cost of the
modifications on these ten vehicles range from $0.50 for the Chrysler 6-
cylinder vehicle to $13.25 for the Ford vehicles.
The Ford control system listed in Table III is the one that Ford
has already developed to meet a 6 g/test standard. As indicated in
Table III, Ford estimates the cost of this system as $15.00. This
agrees quite well with the value of $13.25 which was obtained by summing
the costs of the major components of the system. GM and Chrysler did
not supply cost information for the modifications listed. Using the
Ford cost estimate of $15.00 for the Ford system and the cost estimate
as described above for the GM and Chrysler vehicles, the average costs
of the GM, Ford, and Chrysler systems listed in the Table III are $3.75,
$15.00 and $2.25 respectively. A sales weighted average of these costs
(2)
Based on sales data in "Automotive News Almanac," 1975 and "Automotive
News," Mar. 22, 1976.

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Table I. Summary of Vehicle Modifications and Costs in
Achieving a 6.0 g/test Level (EPA Contract No. 68-03-2172)
Vehicle
Modifications
Cost, S
'75 Ford
Canister replacement with PCV purge

1.00

Seal carburetor leak

0.30

Barrier in air cleaner

0.20

Air cleaner sealing

0.30

Canister bottom cap

0.20


Total
2.00
'75 Pontiac
Bowl vent to canister

0.50

Seal carburetor leak

0.30

Air cleaner sealing

0.30


Total
1.10
'75 Chrysler
Canister replacement

4.00

Canister bottom caps

0.40

Bowl vent to canister

0.50

Barrier in air cleaner

0.20

Seal carburetor leak

0.30

Air cleaner sealing

0.30


Total
5.70
'74 Hornet
Seal carburetor leak

0.30

Bowl vent to canister

0.50

Air cleaner sealing

0.30


Total
1.10
174 Mazda
2 bowl vents to canister

1.00

Canister installation

6.00


Total
7.00
'74 Volvo
Canister replacement

1.00

Heat shield between tank



and muffler

1.00


Total
2.00

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Table II. Summary of Vehicle Modifications and Costs in
Achieving a 2.0 g/test Level (EPA Contract No. 68-03-2172)
Vehicle
Modifications
Cost, $
'75 Ford
Canister replacement

1.00

Seal carburetor leak

0.30

Barrier in air cleaner

0.20

Air cleaner sealing

0.30

Canister bottom cap

0.20


Total
2.00
'75 Pontiac
Bowl vent to canister

0.50

Seal carburetor leak

0.30

Air cleaner sealing

.30

Canister replacement with PCV purge

1.20


Total
2.30
'75 Chrysler
Canister replacement

4.00

Canister bottom caps

0.40

Bowl vent to canister

0.50

Barrier in air cleaner

0.20

Seal carburetor leak

0.30

Air cleaner sealing

0.30


Total
5.70
'74 Hornet
Seal carburetor leak

0.30

Bowl vent to canister

0.50

Air cleaner sealing

0.30

Canister replacement with PCV purge

1.00

Canister bottom cap

0.20

Barrier in air cleaner

0.20


Total
2.50
'74 Mazda
2 bowl vents to canister

1.00

Canister installation with PCV purge

7.00

Underhood ventilating fan

17.00

Canister bottom cap

0.20


Total
25.20
'74 Volvo
Canister replacement

1.00

Heat shield between tank



and muffler

1.00


Total
2.00

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Table III. Estimated Increase in Vehicle Retail Price for
Manufacturer Designed and Tested Systems Which Have
Yielded Evaporative Losses Less Than 2.0 g/test
No.
Vehicle
Make
Modification Cost, $
1

Oldsmobile
Dry canister (PCV purged)
0.60



Sealed door in air cleaner snorkel
3.40(1)



Bowl vented to canister
0.50



Total
4.50
2

Chevelle
Vapor purge valve (PCV purged)
0.60



Bowl vented to canister
0.50



Internal vent closed
( 1 \



(2-way bowl switch)
4.00



Total
5.10
3

Chrysler
2-way carburetor bowl vent switch
4.00
4

Chrysler
Bowl vented to canister
0.50
5 &
6
Ford
Bowl vent valve
3.00



Enlarged canister
3.00



PCV purged canister
0.60



Auxiliary canister
-3.00



Electronic air cleaner door
3.40



New gas cap
0.25



Total 13.25
(15.00)(2)
7

Oldsmobile
Manually operated carb. bowl switch
3.00
8

Oldsmobile
Vacuum operated carb. bowl switch
3.00
9

Oldsmobile
Bowl vent to canister
0.50



Door in air cleaner snorkel
3.40



Total
3.90
10

Oldsmobile
Manually operated carb. bowl switch
3.00
(1) From manufacturers' comments on "Proposed Evaporative Emission Regulations
for Light Duty Vehicles and Trucks", January 13, 1976.
(2) Ford's estimate for this system submitted to the EPA on February 27, 1976.

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results in an estimated retail price increase (as calculated in Exxon's
contract work) to reduce evaporative emissions from the current production
level to 2.0 g/test of $7 per vehicle.
c. The cost-effectiveness of emission control strategies is
commonly presented in units of dollars- per ton of pollutant removed. To
calculate such a cost-effectiveness for evaporative emission control, it
is convenient to express the evaporative emission reduction in units of
g/day and then g/mi. To calculate g/day, a relationship between the
quantity of hot-soak and diurnal emission must be assumed. Based on
Exxon test results under Contract No. 68-03-2172, it is assumed that
vehicles at a 6 g/test level will emit 80% during the hot soak test and
20% during the diurnal; and vehicles at a level of 2 g/test will emit
60% during the hot-soak and 40% during the diurnal.
The above assumption, along with th^. assumption that the average
vehicle undergoes 3.3 hot-soaks per day , results in evaporative
hydrocarbon (HC) emissions of 17 g/day for a 6.0 g/test level vehicle, and
4.8 g/day for a 2.0.^/test vehicle. Assuming that the average vehicle
travels 29.4 mi/day , the 6.0 g/test level vehicle and the 2.0 g/test
vehicle emit 0.58 and 0.16 g/mi of HC evaporative emissions, respectively.
The reduction in decreasing from 6.0 g/test to 2.0 g/test is 0.42 g/mi.
Assuming a vehicle lifetime of 100,000 miles, this reduction in HC
emission over the lifetime of the vehicle is 0.046 tons.
The contract work done by Exxon showed that the estimated sales
weighted increase in vehicle retail price in going from a 6.0 g/test level
to a 2.0 g/test level was $1. Estimating the associated reduction in HC
emission over the life of the vehicle as 0.046 tons, the cost effective-
ness is $22/ton.
The sales weighted cost estimate for the manufacturer's experi-
mental systems which achieved 2.0 g/test was $7. This is $5 greater than
the $2 cost of the Exxon modifications used to achieve a 6.0 g/test level.
Assuming this $5 incremental cost, the cost effectiveness of going from
6.0 g/test to 2.0 g/test becomes $109/ton.
4. Summary
The cost effectiveness of removing HC emissions via reducing light
duty vehicle and truck evaporative emissions from 6.0 g/test to 2.0 g/test
has been estimated from both EPA contract study and manufacturers'
supplied data. The cost effectiveness values obtained from these two
sources of data are $22/ton and $109/ton, respectively. The true cost
effectiveness of reducing evaporative emissions from 6.0 g/test to 2.0
g/test on a nationwide basis is expected to be between these two estimates.
(3)
"Compilation of Air Pollutant Emission Factors, Supplement 5", U.S.
EPA, December 1975.

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Appendix A

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APPENDIX V
TABLE I
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Make:	Ford "LTD"
Year: 75
Ho. :		1_
Displ. cu. in./Litre: 351/5.75
Evap. Emissions,
Modifications		g/SHED Test		Remarks	
I.a. Purge from Inside air cleaner element.
b.	Barrier in air cleaner at base of snorkel.	6.1
c.	Choke shaft passage sealed.
II. Steps a, b, c
d.	Air horn to body gasket modified to allow more bowl	9.6
vapors to be stored in air cleaner.
IlI.e. Purge to air cleaner snorkel as well as air cleaner.
Measurements were made of purge rates for both an air cleaner and a snorkel purge system. Next, a curve
of grams removed from canister vs. total purge volume was made. From these data it was estimated that a
combination air cleaner-snorkel purge system would remove 13 to 15 grams from the canister during the SHED
preconditioning period (4-LA-4s), This is not an adequate system because the combined diurnal and hot soak
input to the canister is about 23 grcrns for the modified vehicle. Consequently, a PCV purge system was installed
using z. 1574 Vega canister which had bcei In daily usage up to this time.
IV. rcV ?
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Attachnent A-II
Table II
Summary of Evaporative Emissions from Modified Vehicles
Make:	Pontiac
Year:	75
No. :	2
Displ. cu. in./Litre: 400/6.56
Modifications
Evap. Emissions,
g/SHED Test
I.a. Vented carb. bowl to canister,
b. Sealed leak around accel,
pump shaft.
10.5 (diurnal)
Remarks
II. Steps a and b
c. Restriction in line from
bowl to canister.
Canister dried up
before run.
3.4
III. Steps a, b, c
d.	Underhood ventilated with
a fan.
e.	Bottom on canister.
1.6
2.5
1.7
Fan lowers carb.
temp, about 30F
NOTE:	Upon completion of these tests, a Vega canister was installed,
and tests were conducted without use of the underhood ventilating
fan. Two repeat tests were performed and results were 1.52 and
1.75 g/test.

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APPENDIX V
TABLE IV
SUMMABY OF EVAPORATIVE EMISSION'S FROM MODIFIED VEHICLES
Make:	Chrysler
Year 75
No.; 21
Diopl.	cu. in./Litre: 440/7.21
Modifications
Evap. Enissions,
r/SHED Test
Remarks
I Original ECS
Original ECS
13.4
14.6
Diurnal - 6<3 g, H.5. - 7.1 g
Diurnal - 4.4 g, H.S. - 10,2 g
II Modified ECS:
\D
M
(a)	Two canisters in parallel used

o
3*
3
CD
3
>
i

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APPENDIX V
TABLE V
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Make:	Hornet
Year:	74
No.:	11
Displ. cu. ln/Lltre: 232/3.80
Evap. Emissions,
Modifications		r/SHED Test
I.a. Carb. bowl vented to the canister.	3.9
b.	Accel, pump shaft leak sealed.
II. Steps a and b above - restriction in line from carb.	3.1
bowl to canister.
c.	Barrier installed in air cleaner at base of snorkel.
III. Steps a, b, c above
d.	Bottom of canister closed.	2.5
IV. ECS modified to a PCV purge system using a 1974 Vega 1	1.2
canister. Steps a, b, c, and d above also continued. f	1.3

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APPENDIX V
TABLE VI
SUMMARY Of EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Make:	Mazda
Year:	74
Ho.:	15
Displ. Cu In./Litre: 80/1.31 (Rotary)
Evap. Emissions
Step	Modifications	r/SHEP Test	Remarks
I	Both carburetor bowls vented to	4.8, 3.8	Hydrocarbon vapors escaping from
a 3 tube canister (Chrysler).	snorkel.
Purge is through existing purge
line to PCV. Original ECS used
for diurnal.
II	Kext, the modifications indicated below were tested. In each case, the hydrocarbon level from the
SHED test exceeded 2.0 grams.
1.	Canister moved outside of engine compartment to a cooler environment.	
2.	Canister dried up on vacuum pump prior to diurnal and hot soak.	
3.	Air cleaner canister closed off and 3 Lube canister used for both diurnal and hot soak.	,
At this point, additional source determination tests indicated hydrocarbon vapors emanating from
carburetor throat due to fuel drippage. To alleviate pressure in the carburetor bowl, a fan
installed to lower bowl temperature by ventilating the underhood engine compartment.
Ill	Modifications for Step I.	2.8
Underhood fan to ventilate
underhood.
At this point, the 3 tub# canister was changed to a A tube Vega with a purge control valve. (Used
canister from 1974 Vega.) High diurnal losses in above runs due to tank vapors passing into engine
crankcase, then through PCV purge line into 3 tube canister. Vapors then moved out of the canister
into the carburetor bowl and air cleaner through the vent line from the bowl to the canister. The	^
purge control valve prevents this migration of vapors into the carburetor bowl and air cleaner.	
IV	Modifications for Step I with	1.8, 1.3	S*
exception of replacing 3 tube	%
canister with a 4 tuba unit.	5.
rr
Fan to ventilate underhood,	>
<

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appendix V
TABLE VII
SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES
Make: Volvo
Year:
No.:
74
17
Displ. cu. in./Litre: 121/1.98
Modifications
I.a* Equalizing valve modified so as to relieve fuel tank
pressure at 0.5 psig.
b. Baffle Installed between fuel tank and muffler.
c American Motors canister used.
Evap. Emissions,
g/SHED Test
0.4
1.7
Remarks
CO and HC exhaust levels
higher with modified ECS.

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TABLE II. SHED Evaporative Tests on Vehicles Tested Under Contract No. 68-03-2172.

ECS
Evaporative Emissions, g
Exhaust
Emissions
, g/mi(1)

Condi-
No. of
Average
Average
Total



Vehicle r
Engine tion
Tests
Diurnal
H. Soak
Range
Average
HC
CO
NOx
'75 Ford
351-2bbl Stock
2
3.4
3.2
6.2 -7.1
6.7
0.54
6.75
1.62

Modified
2
0.2
1.0
1.2 -1.3
1.2
0.52
4.44
1.87
'75 Pontiac
400-4bbl Stock
2
0.4
7.1
7.2 -7.8
7.5
0.80
6.95
1.31

Modified
3
1.2
0.7
1.6 -2.5
1.9(2:
0.68
4.05
1.36
'74 AMC
232-lbbl Stock
2
0.5
10.3
10.8 -10.8
10.8
1.50
24.5
1.24

Modified
2
0.3
0.9
1.2 -1.3
1.2
1.51
26.9
1.13
'74 Mazda
80-4bbl Stock
2
0.2
10.4
10.5 -10.7
10.6
2.11
11.7
0.88

Modified
2
0.6
0.9
1.3 -1.8
1.5
1.82
9.90
0.65
'74 Volvo
121-FI Stock
2
4.7
3.2
7.1 -8.7
7.9
0.91
13.3
2.15

Modified
2
0.7
0.4
0.4 -1.7
1.1
1.24
22.6
1.58
'75 Chrysler
440-4bbl Stock
2
5.3
8.6
13.4 -14.6
13.9
2.32
23.2
1.98
	
Modified
2
0.6
1.3
1.9 -2.0
1.9
1.10
13.3
1.83
(1)
(2)
Average of 2 or more tests
This data is for an underhood ventilating fan system. A PCV-purged canister system was later
tested on this vehicle and average 1.6 g/test for 2 tests.

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Appendix B

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Attachment Bs-I
-4-
TABLE III. Manufacturer's SHED Evaporative Tests on Experimental
Control Systems.
Vfehicle


No. of
Average
Emissions,
8
No * Make
Engine, C1D
Carburetor
Tests
Diurnal
Hot Soak
Total
i Oldsmobile^
455
4 bbl
1
0.33
1.17
1.50
2 Chevelle(2)
250
1 bbl
1
0.64
1.23
1.87
3 Chrysler^
318
2 bbl
1
0,42
1.31
1.78
4 Chrysler(A)
225
1 bbl
7
0.72
1.05
1.78
5 Ford(5)
302
-
3
-
-
1.45
6 Ford<5)
400
-
3
-
-
1.54
7 01dsmobile(6)
455
4 bbl
1
0.85
1.07
1.92
8 ''dsmobile^
455
4 bbl
1
0.74
0.96
1.70
9 ^xdsmobile^
-
-
1
0.80
0.92
1.72
10 Dldsmobile^
-
-
2
0.48
1.18
1.66
(1)	Dry canister, closed air cleaner snorkel during hot soak and float bowl
vented to canister.
(2)	Vapor purge valve, float bowl vented to canister and internal vent closed.
(3)	2-way carburetor bowl vent.
(4)	Carburetor bowl vent to canister.
(5)	Bowl vent valve,PCV purged enlarged canister, auxiliary canister, electronic
air cleaner door and new gas cap.
-(6) Proposed production ECS design with manually operated carburetor bowl switch.
(7)	Proposed production ECS design with vacuum operated carburetor bowl switch.
(8)	Experimental V-8 engine with bowl vent and air cleaner door, 1978 prep.
(9)	Experimental V-8 engine with manual bowl vent switch, 1976 prep.

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APPENDIX to the ANALYSIS OF COMMENTS

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