71-19
Exhaust Emissions From Three Low-Emission Vehicles
Using Catalytic Converters
January 1971
John C. Thomson
Division of Motor Vehicle Research -and Development
Air Pollution Control Office
ENVIRONMENTAL PROTECTION AGENCY
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Vehicles Tested
The exhaust emission characteristics of three prototype
low-emission vehicles were investigated using standard
tests. All vehicles were full sized luxury type with large
displacement engines. Each vehicle was equipped with an
automatic transmission and air-conditioning. Vehicle #1
used a modified choke system, exhaust gas recirculation,
air injection and a charcoal canister to collect unburned
hydrocarbons from the exhaust during the cold portion of
the test. This vehicle was equipped with a single cataly-
tic reactor for oxidation of exhaust hydrocarbons and car-
bon monoxide. Vehicle #2 also had a modified choke, exhaust
gas recirculation and air injection. This vehicle used two
catalytic reactors, one for oxides of nitrogen reduction and
one for oxidation of hydrocarbons and carbon monoxide. Spe-
cial controls to reduce the amount of ammonia were also pro-
vided. Vehicle #3 used similar choke modifications and
exhaust gas recirculation. This vehicle was equipped with
air injection and a catalytic reactor. In order to reduce
emissions during the cold portion of the test a special
fuel with a modified distillation curve was provided. All
vehicles were tested using tank fuel which was reported to
be low octane lead free fuel.
Tests Conducted
The following tests were performed on these vehicles:
1. Standard 1970'Federal test procedure for exhaust
emissions (FTP).
2. Closed, constant volume sampling technique using
nine repeats of the Federal emissions test cycle (9X7).
3. Closed, constant volume sampling technique using
the LA4-S4 driving schedule as developed for 1972 and
later new vehicle certification (LA4).
Bag samples taken during closed cycle tests were analyzed
using non-dispersive infrared analysis (IR) for carbon Mono-
xide and carbon dioxide, flame ionization detection (FID)
was used for hydrocarbon analysis. In order to compare
oxides of nitrogen measurements with data taken on other
vehicles, a variety of techniques were used. A modified
Saltzman (Saltz) technique was used for wet chemical analysis,
a chemiluminescent technique (CI), and an electrochemical
(NOX Box) technique were also used. All results are reported
as N02 and have been corrected for humidity using the following:
N02 measured.
N02 corr = 1-0.0047 (H-7Sf
where H is the humidity in grains of water
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During some LA4 tests a determination of relative reactivity
was obtained using an APCO developed subtractive column
technique.
When open cycle tests are run non-dispersive infrared
oxides of nitrogen data is taken.
Emission Results
All of the data taken during the test period is reported in
Tables 1 through 3. Vehicle #1 showed the lowest emission
values, but even this vehicle was not consistently below
the 1975 emission standards of 0.46 grams per mile (gprn)
hydrocarbons, 4.7 gpm carbon monoxide and the anticipated
0.4 gpm oxides of nitrogen. All three vehicles showed
quite low emission values but none met the NOx emission
requirement. In Table 4 the relative reactivity of the
various vehicle's exhaust is shown. The values for the
fuel used are not available for conversion comparisons.
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Conclusions
All three vehicles showed considerable emission reductions
relative to present production vehicles. Since the vehiclE~s
were experimental prototypes with very little durability
(it took two tests to determine that the charcoal canister
system was inoperative during the initial tests due to a
bent control arm from delivery) there was no attempt to
evaluate operation off of the dynamometer. It is expected
that a considerable driveability loss could be expected
based on dynamometer evaluations.
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Table 1
Vehicle #1 Single converter
HC CO C02 NOx NOx NOx NOx
Test Type FID IR IR Saltz Cl NOxBox IR
LA4 CVS 4 0.5 2 583 1.0 0.7
CVS 5 0.4 3 923 0.9 1.0
FTP 0.2 4 1.0
9x7 CVS 5 1.0 4 931 1.0 1.3 1.6
LA4 CVS 5* 0.4 3 913 1.0 0.7 1.2
*Cold storage in operation
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Table 2
Vehicle #2 Dual converter
HC CO C02 NOx NOx NOx NOx
Test Type FID IR IR Saltz Cl NOxBox IR
CVS 4 0.9 15 1115 0.5 0.9
LA4 CVS 4 1.3 23 1351 0.8 1.7 0.9
LA4 CVS 5 0.7 8 1135 1.0 1.0
FTP 0.1 4 0.3
9x7 CVS 5 0.7 8 1016 0.8 0.6 0.8
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Table 3
Vehicle #3 Special fuel
HC CO C02 NOx NOx NOx NOx
Test Type FID IR IR Saltz Cl NOxBox IR
CVS 4 0.5 2 1016 1.5 1.7
Ll'\4 CVS 5 0.4 2 927 1.4 1.2
FTP 0.2 1 1..1
9x7 CVS 5 0.5 1 974 1.5 1.9 1.6
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Table 4
Reactivity From Subtractive Data
Single
Dual Converter Converter Special Fuel
#2 #1 #3
P + B* 74% 70% 66%
Olefins 15% 27% 29%
Aromatics 11% 3% 5%
*p + B = Parafins plus Benzene
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