CAB-8/Non-FTP-l
Emissions Under Non-FTP Temperature and Speed Conditions
by
Lois Platte
July, 1978
Characterization and Applications Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air and Waste Management
U.S. Environmental Protection Agency
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After the 1978 model year, Section 202(a)4 of the Clean Air Act (CAA)
prohibits the use of emission control devices or systems which are
designed to comply with the standards if these devices or systems
contribute to or cause unreasonable risk to public health. Tn this
regard, the CAA specifically refers to unregulated pollutants. However,
if the interpretation of this section is extended to the area of currently
regulated pollutants emitted under non-FTP conditions, the problem of
defeat devices which limit control of emissions to FTP conditions can be
attacked. One method of controlling emissions under non-FTP conditions
is to apply the 90% (75% for NOx) reduction requirements of the CAA to
conditions not covered by FTP operation.
Although non-FTP conditions cover a wide spectrum of vehicle operation,
two specific areas are investigated in this memorandum. The relationships
of emissions to non-FTP temperature and speed are examined. The investi-
gation will focus on these relationships for the baseline model years
(1970 model year for HC and CO; 1971 for NOx) to which the percentage
reductions are applied.
Emissions Versus Temperature
Quantitative information on the effects of ambient temperature on
exhaust emissions is available from four sources. One set of data is
provided by the Bureau of Mines in a report entitled Ambient Temperature
and Vehicle Emissions (EPA 460/3-74-028, Oct. 74). In this study, FTP
emissions were collected on 26 vehicles of the 1967-1975 model years at
ambient temperatures of 20°, 50°, 75°, and 110°F. The Bureau of the
Mines data were used to generate the temperature correction equations
for pre-catalyst light duty vehicles for the current version of AP-42
(Mobile Source Emission Factors, EPA-400/9-78-005). The temperature
correction equations are based on the 22 Bureau of Mines vehicles that
are in the 1967-1974 model year category. Plots of average emissions
versus temperature which were developed from the AP-42 equations are
given in Figures 1-3 for HC, CO, and NOx respectively. The figures give
average HC and CO emissions from 1970 model year vehicles and average
NOx emissions from 1971 model year vehicles. The emissions are adjusted
to 50,000 miles. The plotted emissions represent FTP conditions with
the exception of temperature. The AP-42 equations corresponding to
Figures 1-3 that relate emissions to temperature are as follows:
HC: et = .195 ([exp (2.931 - .014779t)] + 3.877
CO: et = .200 [exp (5.6548 - .015965t)] + 44.573
NOx: e =4.43
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No significant changes due to temperature variation were found in NOx
(corrected for humidity) when the temperature correction factors were
generated using all the 1967-1974 data. Therefore, the AP-42 NOx
temperature correction equations and plots are straight lines.
Figures 4-6 are plots of HC, CO, and NOx emissions generated by AP-42
that have been normalized to the emission levels at 75°F. The ratios
given in this latter set of plots may be used as multiplicative factors
to correct FTP emissions at 75° to other temperatures,
As stated previously, the AP-42 emissions versus temperature curves were
generated from test data on 1967-1974 model year vehicles. For this
memorandum, specific interest is on emissions of the 1970 or 1971
baseline model years. Only two 1970 model year vehicles were tested in
the Bureau of Mines study. To expand this sample, the test fleet was
grouped on the basis of similar control technology to give a sample of
seven 1970 and 1971 vehicles which may then be used to represent the
1970 baseline year for HC and CO. The five 1971 model year Bureau of
Mines vehicles were used to represent the NOx baseline year. The
average emission rates for these two groups of vehicles are given in
Table 1 for each test temperature. The temperature specific average
emissions normalized to the average emissions at 75° are also given.
The average emission levels of the two groups of baseline vehicles have
been compared with the emission rates as generated by AP-42 calculations
in Figures 1-6. The biggest difference between the actual emissions of
the baseline vehicles and the AP-42 emissions occurs at low temperature.
The temperature information from the other three data sources is limited
because these sources have few, if any, vehicles representing the
baseline years. The Canadian Cold Weather Fleet consists of only 1975
model year vehicles and is therefore excluded from further examination.
Although limited, the emissions from pre-catalyst vehicles taken from
the remaining two sources of temperature effects data are summarized for
reference and comparative purposes.
A paper entitled CO Hot Spot Preliminary Investigation prepared by the
Technology Assessment and Evaluation Branch (December, 1977) is a report
on vehicles that were tested at 75°F after soaking at 10-25°F and 68-
86°F for various time periods. Only two pre-catalyst technology vehicles
were tested in this study. The overnight soak data for these too 1970
model year vehicles are summarized in Table 2.
As a part of the FY77 Emission Factor Program (EFP), twenty 1972-1974
model year vehicles were tested once at low ambient temperature (any
prevailing temperature less than 60°F) as well as at the regular FTP
temperature conditions. No 1970-1971 model year vehicles were tested in
this program. The average ratios of emissions at low temperature to
emissions at the FTP temperature are given in Table 3.
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Emisslons Versus Specd^
The other aspect of non-FTP conditions examined in this memorandum is
the relationship of emissions to average speeds. P3ots of emissions
versus average speed are given in Figures 7-9 for HC, CO, and NOx
respectively. The plots were generated from the current AP-42 equations
associating emissions to average speed. The plotted emissions represent
the average emissions at 50,000 miles of 1970 model year vehicles for HC
and CO and 1971 model year vehicles for NOx. Figures 10-11 show the AP-
42 emissions normalized to emissions at 19.6 mph. The latter set of
figures gives ratios that may be used as FTP correction factors for
average speed. In Figures 7-11, the temperature conditions, percent of
hot/cold operation, and the proportion of average bag speed to average
cycle speed are kept at FTP levels. The normal FTP conditions of these
variables may not represent realistic driving situations particularly
xchen average speed is very much higher or lower than the FTP average
speed.
Some emissions data on the baseline model year vehicles are available
for the New York City Cycle (NYCC) and the Highway Fuel Economy Test
(HFET) which were developed to reflect realistic characteristics of
specific types of low speed and high speed driving. The NYCC has an
average speed of approximately 7 mph and is representative of congested
urban driving. As part of the FY75 EFP performed in Phoenix, fifty 1970
and 1971 model year vehicles were tested over both the NYCC and the FTP.
These NYCC tests were conducted as running hot tests. Table 4 gives the
average ratio of NYCC emissions to FTP emissions for these fifty vehicles.
The average ratio indicates that HC and CO over the NYCC are approximately
2 1/4 times greater than HC and CO over the FTP. NOx is not significantly
different on the NYCC as compared to the FTP.
To examine the sensitivity of emissions to speeds higher than the FTP,
HFET data have been examined. The HFET has an average speed of approxi-
mately 48 mph and is representative of relatively free flowing driving
on major roadx^ays. The only available HFET data for the baseline years
were collected as part of the FY73 Emission Factor Program. Sixty-six
1970 model year vehicles and eighty-one 3971 model year vehicles were
tested in this program on both the HFET and the FTP. The average ratio
of emissions on the HFET to emissions on the FTP is given in Table 5.
The information indicates that NOx emissions are between 10-20% higher
on the HFET than on the FTP, while HC and CO are between 50-60% lower on
the HFET.
Summary
The information presented in this memorandum represents a review of
currently available data depicting emission levels at non-LA4 conditions
of temperature and speed. For the baseline model years, the ratios of
emissions at non-FTP temperature or speed to emissions at FTP temperature
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or speed have been presented. These ratios may be used as correction
factors to approximate FTP emissions at non-FTP conditions of temperature
and speed. For model years 1980 and 1981, emission guidelines for
certain non-FTP conditions may be developed by applying these correction
factors to the 1980 and 1981 FTP standards. The emission guidelines
that result for the 1981 model year represent 90% reduction (75% for
NOx) from the baseline for specific types of non-FTP operation.
Tables 6-8 give the 1980 and 1981 HC, CO, and NOx emission guidelines
for the NYCC and HFET at 75°F and for the FTP at 20°, 50°, 110° F.
Emission guidelines for non-FTP temperatures were calculated using the
ratios in Table 1 as well as those of Figures 4-6. In the former case,
the ratios are derived from the mean emission levels of those Bureau of
Mines test vehicles that represent the baseline model years. The
guidelines that result from the baseline vehicle ratios are, in general,
less stringent than the second set of guidelines. The second group of
emission guidelines for non-FTP temperature are given in parentheses in
Tables 6-8. These values are based on the AP-42 emissions versus
temperature curves estimated from the test results of the 1967-1974
model year vehicles in the Bureau of Mines study. The emission guidelines
at 0° F were determined by extrapolating the AP-42 curves to that
temperature.
The NYCC and HFET guidelines were computed using the ratios in Tables 4
and 5, respectively. These ratios are derived from EFP test data
collected from baseline model year vehicles.
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7,53
Temperature versus HC (CMS / M I IE) at 50,000 lilies
1970 Model Year, AP-42
0 10 20 30 UO 50 80 70 80
TEMPERflTURE C'F)
90 100 110
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301
Figure 2
Temperature versus CO I CMS / MILE) at 50,000 Miles
1970 Model Year, AP-42
0
10 20 30
UO 50 60
TEMPERRTURE
80 90 100 110
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i -
Figure 3
Temperature versus MQX (CMS / MILE) at 50,000 Miles
1971 Model Year, AP-42
20*
50
75'
no
u-
0
10 20 30 40 50 60 70 80
TEMPERflTURE C'F)
90 100 110
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4
A
p
rr
H-
O
Figure 4
RflTIO OF HC RT NON-FTP TEMP: HC flT FTP TEMP
1970 Model Year, AP-42
1 .30
1.11
110°
0.90
OT
0 10 20 30 40 SO 60 70 -80
TEMPERRTURE t°F)
90 100 110
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RRTIO OF CO RT NON-FTP TEMPt CO RT FTP TEMP
1970 Model Year, AP-42
rn
3
t— <
o
2;
CO
rr
o'
1-
110 °
0.88
10 20
30
50 60 70
TEHPERflTURE C°F)
80 90 100 110
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Figure 6
RRTJQ OF NOX RT NON-FTP TEMP: NOX RT FTP TEMP
1971 Model Year, AP-42
rn
40
o
2;
CO
y
rr
50_
75'
1 ,00
1,00
1,00
1.00
110'
1.00
0 10 20 30 UO 50 60 70 80
TEMPERRTURE (°F)
90 100 110
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15,82
Avg. Speed versus HC (GHS / MILE) at 50,000 Miles
1970 Model Year, AP-42
6 0 mph
2.73
10
15
20
25 30 35
SPEED CMPH)
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5 mph
94
Figure £
Avg. Speed versus CO (GMS / MILE) at 50,000 Miles
1970 Model Year, AP-42
1 0 mph
22.30
6 Omph
10
15
20
25
30
SPEED
35
50
55
60
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Figure 9
Avg. Speed versus NOX (CMS / H I L E) at 50,000 Miles
1971 Model Year, AP-42
6-
5-
5mph
U.U6
6,o
2-1
l-
10
15 20 25
30 35
SPEED (MPH)
U5 50 55
GO
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figure JLU
RflTIO OF HC flT NON-FTP SPEEDS: HC RT FTP SPEEDS
1970 Model Year, AP-42
USmph
0.58
0.5!
5 > 10 15 20 25 30 35 HO Li5 50 55 60
SPEED CMPH)
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RRTIO OF CO flT NON-FTP SPEEDS: CO fiT FTP SPEEDS
1970 Model Year, AP-42
11.06
2-
10
15 20
25 30 35 HO
SPEED (MPH)
50 ' 55
60
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Figure 12
RflTJO OF NO-X RT NON-FTP SPEEDS: NOX RT FTP SPEEDS
1971 Model Year, AP-42
10
15
20
E5 30 35
SPEED CMPH)
UO
US
50
55
6 0
1.3
60
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Table 1
Average Emissions versus Temperature (°F)
Seven 1970, 1971 Model Year Vehicles
Bureau of Mines Data
HC CO
20° 50° 75° 110° 20° 50° 75° 110'
Average FTP (gm/mi) 5.53 4.62 3.92 3.83 66.3 52.2 37.8 49.8
Normalized to 75° 1.41 1.18 1.00 .98 1.76 1.38 1.00 1.32
Five 1971 Model Year Vehicles
Bureau of Mines Data
NOx
20° 50° 75° 110°
Average FTP (gm/mi) 7.47 7.46 6.32 6.02
Normalized to 75° 1.18 1.18 1.00 .95
Table 2
Average Emissions in Gm/mi Following Low Soak Temperatures
Two 1970 Model Year Vehicles
TAEB Preliminary Investigation of CO Hot Spot
Ratio
Cycle Soal at 10-25°F Soak at ^ 77°F 10-25° Soak; 77° Soak
New York
FTP
Ratio NYC
City
: FTP
HC
29.5
5.30
5.57
CO
387.4
57.7
6.71
NOx
3.10
3.40
.91
HC
8.35
4.25
1.96
CO
244.7
37.8
6.47
NOx
3.65
3.65
1.00
HC
3.
1.
53
25
CO
1.
1.
58
53
NOx
.85
.93
Table 3
Average Ratio of Emissions at Low Temperature (°F): FTP Emissions
Twenty 1972-1974 Model Year Vehicles
Chicago Cold Tests, FY77 Emission Factor Program
Number Tests
HC Ratio
CO Ratio
NOx Ratio
20-30°
5
1.39
1.96
.94
31-40°
9
1.42
1.81
1.04
41-50°
4
1.13
1.29
1.06
51-60°
2
1.14
.84
1.04
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Table 6
HC Emission Guidelines in Cm/mi*
1980 Model Year
Temperature ° F
Cycle
NYCC
FTP
HFET
0°
(.61)
20°
.58 (.53)
50°
.48 (.46)
75°
.86
.41
.20
110°
.40 (.37
1981 Model Year
Temperature ° F
Cycle
NYCC
FTP
HFET
0°
(.61)
20°
.58 (.53)
50°
.48 (.46)
75°
.86
.41
.20
110
.40 (.37
* Two sets of non-FTP temperature guidelines are given:
(1) The values given in parentheses were computed using estimates deriveu
from AP-42 (refer to Figures 4-6).
(2) The other set of guidelines were derived using the computed mean
emission levels of the baseline vehicles tested in the Bureau of
Mines Study (refer to Table 1).
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Table 7
CO Emission Guidelines in Gm/mi*
1980 Model Year
Temperature ° F
Cycle
NYCC
FTP
HFET
0°
(11.6)
20°
12.3 (9.7)
50°
9.7 (8.0)
75°
16.1
7.0
2.9
110°
9.2 (6.2)
1981 Model Year
Temperature ° F
Cycle
NYCC
FTP
HFET
0° 20°
(5.6) 6.0 (4.7)
50°
4.7 (3.9)
75°
7.8
3.4
1.4
110°
4.5 (3.0)
* Two sets of non-FTP temperature guidelines are given:
(1) The values given in parentheses were conputed using estimates
derived from AP-42 (refer to Figures 4-6).
(2) The other set of guidelines were derived using the computed
mean emission levels of the baseline vehicles tested in the
Bureau of Mines Study (refer to Table 1).
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Cycle
Table 8
NOx Emission Guidelines in Gm/mi*
1980 Model Year
Temperature ° F
Oc
20'
50c
75'
110'
NYCC
FTP
HFET
2.1
(2.0) 2.4 (2.0) 2.4 (2.0) 2.0
2.2
1.9 (2.0)
Cycle
Oc
1981 Model Year
Temperature ° F
20° 50'
75'
110'
NYCC
FTP
HFET
1.0
(1.0) 1.2 (1.0) 1.2 (1.0) 1.0
1.1
.9 (1
* Two sets of non-FTP temperature guidelines are given:
(1) The values given in parentheses were computed using estimates
derived from AP-42 (refer to Figures 4-6).
(2) The other set of guidelines were derived using the computed
mean emission levels of the baseline vehicles tested in the
Bureau of Mines Study (refer to Table 1).
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