CORNELL AERONAUTICAL LABORATORY, INC.
Vehicle Research Department
Buffalo, New York 14221
EMISSIONS ANALYSIS OF 54 FLEET-TYPE
PASSENGER VEHICLES
January 197 2
Prepared for
Environmental Protection Agency
Division of Advanced Automotive
Power Systems Development
Ann Arbor, Michigan'48105
-------
INTRODUCTION
Fifty-four 1970-model fleet cars of different makes and mileages
were tested by EPA using both the CVS cold-start and the CVS hot-start
test conditions. On November 15, 19*71, CALi received from EPA the results
of these emission tests with the following remarks: "A two-bag cold start
test was run on each car followed by a two-bag hot start test. To obtain
three-bag data, it is necessary to weight and assemble the data from the
two cold start bags with the first bag of the hot start test using the procedure
described in the Federal Register. " The identity of the vehicles could not
be disclosed by EPA in any way other than by range of engine displacement,
number of cylinders, accumulated mileage, and car weight.
The emission data listed in the computer print-outs gave occasion to
study the following questions:
• To what extent does the accumulated mileage influence the
emissions level?
• Is there a significant difference between the emissions levels
for cold start and hot start?
• What is the numerical relation between the CVS-C and the
CVS-CH testing procedure?
The answers to these questions were felt to provide, by inference, some
inputs into the planning of Stratified-Charge-Engine tests.
1
-------
INFLUENCE OF ACCUMULATED MILEAGE ON EMISSIONS LEVEL
The accumulated mileage of the cars tested ranged from approximately
4, 000 miles to 35, 000 miles. A visual inspection of the emissions data
from an analysis of each bag plotted versus accumulated mileage strongly
suggested negligible correlation between the two variables, Figures 1
through 12. An analysis of variance, described elsewhere, also failed to
reveal a mileage trend (nor did it confirm any other trend associated with
number of cylinders, displacement, and car weight). Hence, all cars can
be considered as drawn from the same homogeneous population.
As an interesting aside, it may be mentioned that in contrast to the
toxic emission components (CO, HC, and NOx), the non-toxic component
of CO2 did indeed reveal a mileage correlation. Figure 13 shows CO2
data in gr/mi for the first cold bag as a function of mileage suggesting an
upward trend of emissions with mileage. An analysis of variance, Table 1,
confirmed the significant contribution of mileage to the overall variability
of COz.
Table 1
Analysis of Variance on CO^ Emissions (gr/mi) of Fifty-
four Cars, Divided into Three Mileage Classes ( < 10, 000;
10,000 - 20,000; >¦ 20, 000 miles)
Source
Sum of Squares
Degree of
F reedom
Mean Square
Between mileage classes
14. 92 x 104
2
7. 69 x 104
Within mileage classes
65. 80 x 104
51
1. 29 x 104
' TOTAL
81.72 x 104
53
F = 6. 17
F rt»5. 0
2,51,99%
2
-------
INFLUENCE OF START CONDITIONS ON EMISSIONS LEVEL
Figures 14 through 17 depict the means and the standard deviations of
the HC, CO, NOx, and CO2 constituents for each of the four bags. The mean
is indicated by a small circle, the standard deviation by the length of the
vertical bar extending from the mean value in both directions. Obviously,
the HC and the CO contents (in gr/mi) of the first (cold-transient) bag are
significantly higher than those of the rest. In fact, the differences between
the second (cold-stabilized), third (hot-transient), and fourth (hot-stabilized)
bag are so slight as to suggest a constant level of CO and HC emissions after
the first bag. Thus, the HC level of the first bag is approximately 1. 6 times
higher than the average level of subsequent bags, and the CO level of the
first bag approximately 3. 4 times higher. The situation is different for NOx.
Here, the NOx content of the first bag is always higher than that of the
subsequent bag regardless of whether the engine is started after a cold soak
or a hot soak. The CO2 level is of lesser importance. We note that it
remains approximately unchanged.
Another descriptor of interest is the standard deviation. In HC and
CO emissions, the standard deviation seems to change proportionally with
the mean, an observation confirmed by analyses of aircraft emission data
(Reference 1). The standard deviations of both NO^ and CO^, however,
indicate no dependence on the mean.
For comparison, the emission data of the 54 cars were contrasted
with the emission data of an FCP engine installed in a jeep (Reference 2).
The FCP data are listed in Table 2 and indicated in Figures 14 through 17
by black bars; the bar center is identical with the mean, the bar length
wit,h twice the standard deviation. The general trends of both plots are
3
-------
similar although the KC, CO, E.cd NO^ vaJu.es of the FCP engine are
strikingly lower than those of the 54 cars (due to effective emission control
and lack of variance between engines).
Table 2
Constant Volume Sampler Results of FCP Engine
EPA, October 7, 1971 (Reference 2}
i
Standard
Rel.
Bag
Size
Gas
Mean
gW mi
Deviation
gr / mi
Variation
%
HC - FID
0. 97
0. 16
16
Cold
14
CO - IR
1. 30
0. 43
33
Start
C02 - IR
480.
45.
9
NOx - CI
0. 40
0. 13
33
HC - FID
0. 18
0. 05
3
CO - IR
0. 78
0. 28
36
Stabilized
14
C02 - IR
509.
37.
7
NOx - CI
0. 28
0. 06
22
HC - FID
0. 27
0. 03
11
Hot
14
CO - IR
0. 76
0. 26
34
Start
COz - IR
451.
53.
12
NOx - CI
0. 39
0. 12
30
4
-------
CVS-C VERSUS CVS-CH TEST PROCEDURE
The Constant Volume Sampling Procedure for 1972 prescribes a 1369
second, 7. 5 mile, non-repetitive driving cycle with a 12-hour cold soak
before testing and a cold start (Notation: CVS-C).
The Constant Volume Sampling Technique for 1975-76 prescribes the
same 7, 5 mile driving pattern as the 1972 procedure. The emissions of the
first 505 seconds are collected in a "cold transient" bag, those of the next
864 seconds in a "stabilized" bag. After ten minutes hot soak with engine
off, the 7. 5 mile driving cycle is repeated with the emissions of the first
505 seconds collected in a "hot transient" bag (Notation: CVS-CH). The
first cold bag is weighted by a factor of 0. 43, the second transient bag by
a factor of 1, and the third hot bag by 0. 57, All weighted emissions are
then added and the sum divided by 7. 5 to give the emissions in gr/mi.
In order to compare the CVS-C and the CVS-CH procedures, the four-
bag data of the 54 cars (a cold-transient bag, a cold stabilized bag, a hot-
transient bag, and a hot-stabilized bag) were assembled in two ways.
CVS-C
Y in gr / mi
m
CVS-CH
{0. 43 Y + Y +0. 57 Y, J/7. 5
ct cs ht
Y in gr/mi
wm 6
Y = mass emissions of pollutant (CO, HC, NOx) as calculated
from the cold-transient phase (bag) of the cold-start test,
in grams
Y = mass emissions of pollutant (CO, HC, NO ) as calculated
OS X
from the cold-stabilized phase {bag) of the cold-start test,
in grams
5
-------
= mass emissions of pollutant (CO, HC, NO^) as calculated
from the hot-transient phase (bag) of the hot-start test, in
grams
= mass emissions of pollutant in gr/mi; CVS-C test procedure
^wm = ma>ss emissions of pollutant in gr/mi; CVS-CH
procedure
These computations were performed for each of the 54 cars (actually only
53 because one car's data were quite erratic and had to be omitted). For
each car, the ratio of Y /Y was then calculated, and the mean and the
wm m
standard deviation of the distribution of these ratios computed. The results
are listed in Table 3 together with the standard deviation of the mean
(s = s//£I).
mean '
Table 3
Comparison of Emission Levels Computed
According to CVS-C and CVS-CH Method
Y = CVS-CH Mass Emissions in gr/mi
wm
Y = CVS-C Mass Emissions in gr/mi
m °
Pollutant
Y /Y
wm m
Mean
Y / Y
wm m
Standard
Deviation
Number
of
Cars
^wm/^m
Standard
Deviation
of Mean
HC
0. 88
0. 07
53
o
o
h—'
CO
0. 71
0. 13
53
0. 02
no2
1. 01
0. 05
53
0. 01
Table 3 demonstrates clearly the attenuating effect of bag weighting as
regards to HC and CO. The HC level is reduced by 12% and the CO level by
even 29%. The NO level, on the other hand, remains unaffected.
x
6
-------
SUMMARY
Fifty-four fleet cars of different makes and mileages, all 1970 models,
were tested by EPA using both the CVS cold-start and the CVS hot-start test
conditions. Although the accumulated mileage of the cars tested ranged from
approximately 4, 000 to 35, 000 miles, a correlation between mileage and level
of CO, HC, NO^ emissions was not detectable. {There was a slight but
significant increase of CO^ with mileage, however.) The mean and the
standard deviations of the CO and HC emissions sampled in the cold-start
bag were significantly higher than those of subsequent bags. The HC mean
of the cold-start bag was approximately 1. 6 times higher; the CO mean,
3. 4 times. Also, the standard deviation of both emissions seemed to change
approximately proportional with the mean. The situation was different for
NO . Here, the mean of the first bag was always higher than that of the
X
subsequent bag regardless of starting conditions. The CO^ level remained
approximately constant for all bags. The results were qualitatively corroborated
(except for mileage effects) by results of emission tests performed by EPA
on one FCP engine installed in a jeep.
An investigation of the effect of bag weighting on the measured emission
level revealed that the CVS-CH technique produces a 12% lower HC level
than the CVS-C procedure and a 29% lower CO level. The NO level remains
x
unaffected.
7
-------
REFERENCES
1. Cornell Aeronautical Laboratory, Inc.: "Analysis of Aircraft
Exhaust Emission Measurements" - CAL No. NA-5007-K,
November 1971.
2. Private Communication: Computer Printout of EPA.
8
-------
Figure 1 - CO Emissions of Cold-Start Bag
Versus Accumulated Mileage
Figure 2 - CO Emissions of Cold-Start Bag 2
Versus Accumulated Mileage
-------
Zoo
100
So-
vSO
SO
2 O
dib.
JPtT
if
-rhit
!Tj
TTt
f~-Tj
ffit
±tt
:$
fr
to
a
.TTT
mn
rnt
:rnd
itn
fH-f
Ttt:
¦"te
m
j t i f
Zi"
lr-:
tiT
4+
1":
i
B
i
r
<53:.-:
Th
t-rrr
jGr
i
§if
35
IE
W]
sai
lLU
See
e
-i-J-i-L
•irr
1 i ; !
3 |7T
rnr
¦uS-
a*
SB3E
m
DD
rir
i5$
1233
M.
+
I !_
nt
rn-
tHf
M-J-'r
IX:
mf
Trrr ¦
.tot:
.J.
"T"
W"
xn:
•QT^-T
na
at.:
Irrxtt
fcti
rrtr
rt:
H-r
EXI
+B?
@E
& i
5SB-
3+; 3
ao so
jo
6d ioo
Figure 3 - CO Emissions of Hot-Start Bag 1
Versus Accumulated. Mileage
Figure 4 - CO Emissions of Hot-Start Bag 2
Versus Accumulated Mileage
-------
Figure 5 - HC Emissions of Cold-Start Bag 1
Versus Accumulated Mileage
Figure 6
- HC Emissions of Cold-Start Bag
Versus Accumulated Mileage
2
-------
to
N)
e>
20 3d S© too
Figure 7 - HC Emissions of Hot-Start Bag 1
Versus Accumulated Mileage
Figure 8 - HC Emissions of Hot-Start Bag 2
Versus Accumulated Mileage
-------
2©
ao ioo
Figure 9 -
NO^ Emissions of Cold-Start Bag 1
Versus Accumulated Mileage
Figure 10 - NO^ Emissions of Cold-Start Bag 2
Versus Accumulated Mileage
-------
Figure 11- NO^ Emissions of Hot-Start Bag 1
Versus Accumulated Mileage
Figure 12 - NO^ Emissions of Hot-Start Bag 2
Versus Accumulated Mileage
-------
Figure 13 - Emissions of Cold-Start Bag 1 Versus Accumulated Mileage
-------
r~_.
Tjil!
> . j
i ' i
i i 1 ;
: i' ' i :
I
j 1 ! i
- 1 1 f !
i i
' • i i
'
i
[ I
! !
; ! S
;
; i
j i
i
1-
i
i
j
<
>
j !
•j
i
m/
Mi
—
(
)
c
)
c
>
I
i
I
!
i
i
1
i
L...
. .
i i
1
¦ i 1
BAG, H\ BAC, ** 2. Bag,* I BAC *3.
col_t> cold hot hot
Figure 14 -
Mean and Standard Deviation of HC
J 54 Fleet Cars
| Jeep with FCP Engine (EPA)
-------
4—
Ft,e
ET C
>
Fi
•
<
>
—UJ
I
.. i
t
t
—k—
Bac, * i T3AC,*a_ Sac,* i Qac,«z
C4LO COLD )+or HOT
Figure 15 - Mean and Standard Deviation of CO
J 54 Fleet Cars
| Jeep with FCP Engine (EPA)
(10 times enlarged)
-------
I
' ' ; i i ; \ ¦
: ; ' ' ' i
r —
•
1 i
I
t
!
j
! ;
i
¦ i ^
i
<
I
<
i
q
m/
<
»
'
i
! |
(
I
| i
'
j
I
:
.
T
— 1
n
j
1
i
. .1
Bag, #i Bac, ** 2. bac, ** i J ac,
c.oi_D c.ov_D Hot Hot
Figure 16 - Mean and Standard Deviation of NO^
^ 54 Fleet Cars
| Jeep with FCP Engine (EPA)
-------
6oo
600
¥00
1
i
1
i ;
f
; 1
S ;
<
i
¦
<
>
<
>
I
jGj
1\
1
/
i
i
i
1 1
1 - 1
i :
i
1 ¦ ! •
¦i ' !
' |
1
|
¦
i
1
|
i
1
i
1
!
\
| •
S
i
i
i
¦ 1
1
2 00
**
COLD
"Bag, *#2.
cx> i~D
13A o, *<
H6T
Hot
Figure 17 -
Mean and Standard Deviation of CO^
J 54 Fleet Cars
| Jeep with FCP Engine (EPA)
------- |