An Examination of Interim Emission Control
Strategies for Heavy Duty Vehicles
(A Regulatory Support Document)
by
The Emission Control Technology Division
Office of Mobile Source Air Pollution Control
United States Environmental Protection Agency
March 30, 1976
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Table of Contents
Page
I.
II.
III.
IV.
V.
Tables
1
2
3
4
5
6
7
Current Heavy Duty Test Procedures and Potential
B. The Relationship of Current Test Procedures
3. Control Technology for Heavy Duty Engines
C. Industry Capability at Various Emission Levels . . .
D. Development Required to Meet Future Standards
G. Additional Technology Assessment Information ....
Comparison of SARR with Preliminary New York City
Truck Data
Comparison of LDV Operation Data from 5 Cities
Relationship Between SARR Emissions and FTP Emissions . .
Expected Percent Reduction in Urban Road Emissions for
Proposed Percent Reductions Measured by the Current FTP .
Percent Reductions in Gasoline Heavy Duty Emissions
Measured by the FTP and Over the Modified UDDS
Ma.iiifcid Vacuum and Corresponding Load Levels
1
4
7
7
8
17
18
19
22
23
23
23
29
32
32
37
38
39
45
1
9
10
14
15
16
17
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Table of Contents (cont'd.)
Tables
8
9
10A
10B
IOC
11
12
13
14
15
Figures
1
2
Page
Summary Chart - Heavy Duty Emissions.
Development Effort to Meet Possible Future HD Emission
Standards
Sanmary Chart Heavy Duty HC Control Technology
Summary Chart Heavy Duty CO Control Technology
Sumnary Chart Heavy Duty NOx Control Technology ....
Preliminary HDV Evaporative Emission Data
Possible Future HD Emission Standards
Cost per Engine Over 1973 Base to Meet Possible Emission
Standards
Background Information on Cost Effectiveness for Various
Control Options
Cost Effectiveness ($/ton) for Various Control Options. .
25
33
34
35
36
37
41
42
47
48
Relationships Between Urban and FTP Emissions for Diesel
Trucks
Schematic Diagram of Proposed Sample Handling and
Analysis System
Fuel Consumption Penalties Estimated by Manufacturers at
California 5 (HC + NOx) /25 (CO) Standard
Combination of HC and NOx Based on 1974 Gasoline
Certification Performance
1974 Certification Sales and Diesel Smoke Emissions-Peak
43
44
References
49
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1. Introduction
Exhaust emissions from heavy duty vehicles (HDV)-were first
regulated in California beginning with the 1969 model year. The
standards applied only to gasoline engine hydrocarbon (HC) and carbon
monoxide (CO) emissions. EPA adopted the California standards and
test procedures in 1970 and added a separate smoke procedure and
standards for Diesel engines covering all 50 states. In 1972 Cali-
fornia lowered the HC and CO standards. In 1973 California revised the
gasoline test procedure to a mass measurement basis, added a standard
for oxides of nitrogen (NOx), established a Diesel engine procedure,
and extended applicability of revised standards to all types of heavy
duty engines. In addition, evaporative HC standards were established
for gasoline fueled vehicles. EPA adopted the 1973 California package
with the 1974 model year except for the evaporative HC regulation.
EPA also added a peak smoke level standard to Diesel engines. For
model year 1975, California has lowered gaseous emission levels and
has proposed very stringent standards for 1977. Except for minor tech-
nical amendments to the regulations, EPA has not proposed any further
changes through model year 1978. Table 1 summarizes the past and
future standards applicable to heavy duty vehicles through 1977.
Past and Future Heavy Duty Emission Standards
(a)
Pollutant
Hydrocarbons
Oxides of
Nitrogen
Carbon
Monoxide
Smoke (d)
Opacity
Evaporative
"Kvdrocarbons
1<
C
275
NR
1.5
NR
NR
(c)
J69
F
(b)
NR
NR
NR.
NR
NR
19
C
275
NR
1.5
AC,
NR
(c)
fO-1
F
275
NR
1.5
20.NR
NR
1<
C
180
NR
1.0
NR
(c)
>72
F
275
NR
1.5
NR
197
NR
(a) -C - California. F - Federal
(b) NR - No Requirement
(c) HC = PPM CO = % mole volume
(d) % Opacity: Acceleration, Lug, Peak
(e) California test procedure modified to state standards in
teras of gm/BH?-HR. Diesel engine added to requirements.
(f) Evaporative emissions restricted. 2 grams per test - certified
by design.
(g) California test procedure adopted. Diesel engine added to 49
states. HC and NOx combined to a single standard.
(h) HC + NOx = -GM/3EP-HR, CO = GM/BHP-HR.
(i) Alternatlvt standards of HC = 1.0 GM/BHP-HR, NOx =7.5 GM/BHP-HR,
ar<- provided for the manufacturers option.
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ABSTRACT
The Emission Control Technology Division of the Office of Mobile
Source Air Pollution Control has examined the need for, and possible
strategies for, achieving reductions in gaseous and smoke emissions
from heavy duty vehicles and their powerplants. The relationship of
existing test procedures to urban mass emissions, the technology
available to meet reduced emission levels, the cost of various con-
trols and their effectiveness are each examined in arriving at an
optimum strategy for near term application to heavy duty vehicles.
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The test procedures associated with heavy duty vehicles are
engiae dynamometer exercises at steady state conditions. Unique pro-
cedures are applied to the gasoline and Diesel engines. These exercises
are described as "9" and "13 mode" tests respectively. The Diesel
smoke test procedure is a unique and separate transient test procedure.
The original heavy duty engine standards represented a very small
improvement over uncontrolled levels for HC and CO. The 1974 California
and 1975 Federal standards at best represent a 55% reduction for gaso-
line engines and almost no reduction for Diesel engine gaseous emissions.
This contrasts vith the 80 + %* reduction in light duty vehicle emissions
represented by che 1975 interim standards. In addition, long range
agency planning documents (1) have assumed equitable treatment of all
canejcries of mobile sources. Although past assumptions need not
restrict fucure regulatory action, continuation of mobile source con-
trol strategies, which are less stringent than LDV strategies, affects
the air quality impact basis upon which previous decisions have been
.n£.de. These factors, coupled with the fact that current and proposed
stancards for control of other mobile sources are not sufficient to
allow achievement of national ambient air quality standards, suggest
a need to examine heavy duty vehicle control strategies for the years
to come.
The information presented and analyzed in this report is aimed at
identification of a cost effective emission control strategy for short
term application ot heavy duty vehicles and their power plants. The
analysis is based on the assumption that recently proposed revisions
to the definition of Light Duty Truck will be adopted such that heavy
duty will encompass primarily vehicles over 8500 pounds gross vehicle
weight rating (GVWR)(2). Those trucks in the range of 6000 to 8500
pounds GVWR, formerly heavy duty, will become light duty. Thus, in
terms of 1973 sales data the heavy duty class would be approximately
4C% of its former size (3). On a vehicle miles travelled (VMT) basis
the revised light duty truck class and heavy duty class represent 60
and 40% of total truck VMT respectively (4).
The objective of the report is to provide answers to the following
broad questions and to adequately address the issues contained therein.
1. What level of control is technologically feasible for heavy
duty gasoline and Diesel engines?
2. What costs are associated with the various technology options
over the useful life of the vehicles?
*NOx excepted.
(1) Numbers in parenthesis correspond to references listed on the
last p
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3. To what extent are reductions measured by current test pro-
ceaures real reductions in urban emissions?
4. Should HC and NOx as well as gas and Diesel engine designs
be treated on a separate standards basis in the short term?
5. What optimum regulatory approach is appropriate for applica-
tion to heavy duty vehicles including standards, test pro-
cedures and time phasing?
The report presents conclusions and recommendations immediately
following the introduction. Following the conclusions, section III of
the report examines the current heavy duty vehicle control strategy.
Included are detailed discussions of test procedures, their relation-
ship to on the road emissions and needed improvements. The existing
standards and the issue of separate versus combined standards are
treated.
Section IV explores the availability of technology and the levels
cf control achievable, and the impact of proposed California standards
is described. The fifth section presents cost effectiveness calculations
and comparisons to other mobile source strategies.
The need for additional emission control of mobile sources as well
as the environmental and economic impact of the several control strategies
are found in the Environmental and Inflationary Impact Statement (Ref.
#16) .
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-I. Sur..iuiry of Conclusions and Recommendations
The current Federal Heavy Duty engine dynamometer test procedures
(FTP) were carefully examined in terms of their inherent technical
weaknesses and resulting ability to estimate actual emissions of in use
trucks on an urban road route. The result of this examination was
the identification of mathematical relationships for predicting road
route emissions from FTP measurements. In general, there was good
statistical correlation between the FTP and road route for all consti-
tuents except Diesel CO emissions. However, the existing tests were
found to be poor "predictors" of CO and NOx emissions in that a given
reduction in terms of FTP emissions results in a much smaller reduc-
tion, in actual road emissions. This is partially explained by the lack
of certain characteristic operating modes in the current procedures as
well as improper mathematical weighting of the existing modes. Thus,
there is clearly a need to develop procedures and operating exercises
which correlate one for one with urban emissions. However urban
emission reductions, especially hydrocarbons, can, with the current test
procedures, be estimated with reasonable confidence as an interim step.
Several procedural and instrumentation improvements were also
identified as necessary to make it possible to measure advanced control
system engines with reasonable accuracy. A revised sampling and analy-
tical system using chemiluminescence and flame ionization for measure-
ment of total NOx and hydrocarbon has been developed. In addition, the
gasoline 9-mode test reference points were redefined in terms of percent
load instead of manifold vacuum. Equivalence ratios for adjusting the
standards to account for changes in the procedure have been developed
from preliminary data. The effect of substituting an FID for NDIR on
HC measurement is a multiplicative increase of 1.3 to 1.4. 1.4 was used
in determining proposed standards. The effect of substituting chemi-
luminescence and a converter for NDIR on NOx is a multiplicative factor
of .9 to 1.0. Equivalence was assumed in determining proposed standards.
The issues of having unique standards for gas and Diesel and
separation of currently combined HC and NOx constituents were examined.
Both types of powerplants potentially provide the same service function
and there are no data to quantify any potential difference in stringency
between the two test procedures. Therefore, no justification exists
for having unique standards.
The agency has determined that oxidant control is best approached
through control of hydrocarbons, while ambient NOx levels are the major
justification for NOx control. Therefore, there is no long term justi-
fication for continued combination of HC and NOx as a single standard.
However, tradeoffs have already been made between the two constituents;
yet, for the short term:r~s~ome~~ihcentive can be given to control of
HC by stating a separate HC standard and continuing with a combined total
KG + NOx standard. This approach is recommended for an interim step.
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The availability of emission control technology to apply to heavy
duty engines, the level of control achievable, and the expected capa-
bility of the various manufacturers to apply such techniques to pro-
duction engines were examined. Very low levels of emissions (90% from
a 1972 baseline) were achieved in laboratory experiments using combi-
nations of oxidation and reduction catalysts and EGR on several heavy
duty engines. However, reduction catalysts have not been used in pro-
duction automobiles or trucks. Therefore, of the three, only oxidation
catalysts and EGR are considered viable control techniques for an
interim strategy.
Manufacturers' data were solicited in a series of individual meet-
ings to determine their positions regarding achievable future standards.
Although several have engines capable of meeting the 5 gram HC + NOx and
25 gram CO standards proposed by California for 1977, rather severe fuel
penalties for the gasoline engine of at least 7% and 3 to 5% for Diesel
as well as restricted availability and substantial first cost increase
can be expected. Attention was focused on levels of emissions achiev-
able with no increase in brake specific fuel consumption (BSFC). Levels
of control achievable both with and without catalyst technology were
initially determined. Subsequently, as a result of certification of
engines to 1975 California standards and additional information supplied
to the California Air Resources Board in hearings held February 4, 1975,
these initial determinations were revised. It .has now been determined
that levels of 1.5 HC, 25 CO, and 10 HC + NOx (gm/BHPHR) are achievable
by both gasoline and Diesel engines with no increase in BSFC by-1978,
using "good" non catalyst technology. This includes improved fuel
management, air pumps and some utilization of EGR. Diesel engines, many
of which already meet the proposed HC and CO standards, are expected to
utilize several different approaches including EGR, improved fuel injec-
tion and turbochatgers to meet the proposed NOx level.
The ability to reach the previously listed gaseous emission stan-
dards with no fuel penalty was based on the assumption that no further
reductions in smoke levels would be required. However, examination of
current (1975)'certification performance exposed the fact that nearly
all Diesel engine.families have demonstrated the ability to meet a peak
smoke level of 35% opacity. The standard is 50% opacity. Therefore, in
order to prevent manufacturers from actually increasing smoke levels as
a tradeoff against reaching the proposed interim gaseous standards, a
35% peak smoke standard is recommended.
Heavy duty gasoline fueled vehicles are not currently covered by
any evaporative hydrocarbon standard except in California where they
must meet the light duty standard of 2 grams/test. California specifies
the federal light duty test procedure, but certifies the system by
design evaluation rather than requiring confirmatory testing of com-
pleted vehicles. The degree of evaporative control achievable using
current automobile test methods was examined using preliminary data from
heavy duty trucks. It appears that although some control of evaporative
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losses can be achieved, if EPA were to now adopt California practices
for heavy duty vehicles, much more cost effective control would be
possible with a properly designed enclosure based test procedure.
Therefore, it is recommended that control of heavy duty vehicle evapo-
rative losses be deferred until such a test procedure and appropriate
compliance method can be determined.
The cost effectiveness of heavy duty vehicle interim control was
calculated an! compared to other mobile source control alternatives.
An increased first cost of approximately $110 per gasoline fueled vehicle
can be associated with che proposed standards. The $120 estimated in-
crease in Diesel engine cost amounts to less than 0.1 cent per mile
additional operating expense because of the limited first cost increase.
Lack of a fuel penalty for either gasoline or Diesel engines, results
in heavy duty interim emission control at least as cost effective as
control of LDVs and LDTs to interim levels, and more cost effective
thar. other anticipated mobile source emission control strategies.
For the reasons outlined in this summary and others detailed in
the report to follow, it is recommended that the agency adopt an interim
control strategy for application to heavy duty vehicles beginning in
model year 1979. Standards of 1.5 HC, 25 CO and 10 HC + NOx (gm/BHP-HR)
exhaust emissions with 35% peak smoke opacity should be proposed by
NPRM as soon as possible.
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III. Current Heavy Duty Vehicle Test Procedures and Potential Improve-
ments ;
This section of the report examines the exiting test procedures,
their origins, limitations, and potential Improvements. In addition,
the current standards and the issues of equivalent gas and Diesel and
combinatorial HC and NOx standards are examined.
A. Test Procedures;
1. Current Methods and Their Weaknesses.
Two test procedures currently exist for examination of heavy duty
engine gaseous emissions. The "9-mode" and "13-mode" FTP are applied to
gasoline fueled and Diesel engines respectively. The test procedures
are developments of industry, the 9-mode from MVMA and the 13-mode from
EMA, promulgated originally by the State of California and later adopted
by EPA without substantial modification. Additionally, a separate smoke
test procedure, developed by EPA, which simulates worst case transient
manuevers for acceleration and engine lug down is applied to Diesel
engines.
The existence of two separate gaseous emissions test procedures is
explained by an examination of two factors. First, the gasoline engine
was the first of the two types of engines to be controlled in 1969 with
Diesel regulation deferred until 1973. Therefore, the gasoline proce-
dure was developed before a need to control Diesels was recognized.
Secondly, a Diesel engine cannot be run on the gasoline test procedure
because manifold vacuum, the control parameter in the "9-mode" test does
not exist on the unthrottled Diesel. In addition, the 2000 rpm constant '
speed of the "9-mode" test, although characteristic of gasoline engines,
is closer to maximum speed for most Diesel engines.
Both gaseous emission test procedures have several inherent character-
istics which limit their usefulness for accurate assessment of urban
emissions. These include:
a. Steady state operation at each of the mode test points.
Actual road usage involves transient operation involving
continuously changing acceleration and deceleration rates.
b. Single speed (2000 prm) for the gasoline 9-mode and dual speed
(60 and 100% of rated engine RPM) for the Diesel 13-mode.
c. No consideration of cold start influences, as both tests begin
from a "warmed up" engine condition.
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8
d. Lack of a wide open throttle (full load) test point for the
gasoline 9 mode.
e. Weighting factors for the variousmodes have questionable
relationships to overall urban vehicle use patterns.
f. Specification of gasoline 9 mode reference points in terms of
manifold vacuum. The use of manifold vacuum is impossible for
supercharged engines and the level of manifold vacuum is
affected by application of advanced emission control technology
such as EGR.
g. The gas analyses systems use NDIR for all gaseous emissions
except Diesel HC measurement. These methods are inaccurate
for HC and NOx and are especially unsuitable for application
to any lower standards than those that currently exist.
Because of these primary problems, it was necessary to evaluate to
what extent the current procedures related to urban mass emissions and
also develop technical improvements in the test procedure and instrumen-
tation system.
B. The Relationship of Current Test Procedures to Urban Mass
Emissions
The extent to which changes in heavy duty vehicle standards measured
with the current test procedures relate to changes in actual urban on-
the-road emission was evaluated. Southwest Research Institute (SwRI)
has performed warmed-up emissions testing of heavy duty gas and Diesel
trucks over the San Antonio Road Route (SARR), an actual urban road
network. (5,6) At the present time, EPA is analyzing extensive HDV
operational data in New York and Los Angeles with a smaller data base
from St.- Louis. These data will be used to develop representative HDV
chassis driving cycles (speed vs. time) and representative HDV engine
driving cycles (RPM and load vs. time). If necessary, distinct rep-
resentative driving cycles will be determined for buses, 2 axle gas
trucks, 3 axle gas trucks, tractor trailer gas trucks, 2 axle Diesel
trucks, 3 axle Diesel trucks, and tractor trailer Diesel trucks. These
cycles will consider hot/cold weighting factors and will be generated
using MonteCarlo techniques from a data base consisting of over 350
truck days of operational data. Until this analysis is complete, some-
time in 1976, EPA does not have definitive information on how repre-
sentative a given driving cycle is. Table 2 compares summary statistics
over the SARR with preliminary truck operational data from New York
City.
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Table 2
Comparison of-SARR with Preliminary New York City Truck Data
Percent Time Average Speed Percent of time at various speeds (mph)
at Idle Range Speed Range Idle £10 10.01-2020.01-3030.01-40
(mph) (mph) _____ «__»_ «..______, ,
SARRa/ 8.7-29.5 19.6 17.2-25.9 19.0 10.0 20.4 31.8 10.3
NYC b/12.1-61.4 11.6 3.2-17.3 37.5 20.8 17.2 10.3 6.2
a_/ Reference 5
b_/ Reference 7
Exanination of this table indicates the trucks in New York City tend
to have lower average speeds and spend more time at idle than trucks
driven ovsr the SARR. One major reason for this is that the SARR re-
presents truck operation over an origin to destination route. NYC
a^-ta, on the other hand, represent truck operation on a daily basis
aiid as a. result, incorporate idle time accumulated between trip
deliveries. This factor may partially account for the difference in
percent of time spent at idle and average speed although SARR and NYC
results do overlap on an individual truck basis. It is thought that
a more major reason for the apparent difference can be attributed to
the extreme traffic congestion which exists in NYC.
The Vehicle Operations Survey (CAPE-10), conducted under joint
sponsorship of EPA and the CRC, supports this hypothesis. (7) The
purpose of the VOS study was to define, determine, and'typify auto-
mobile driving patterns in terms of operating modes. Data were col-
lected in five major metropolitan areas (New York City, Chicago,
Cincinnati, Houston, and Los Angeles) and subsequently combined to form
an overall composite of urban driving patterns. Of special interest is
the fact that automobiles in New York City have lower speeds and'spend
more time at idle than do automobiles in the other four cities. These
results are shown in Table 3.
The LDV results shown in the table would support the hypothesis
of lower average speeds and higher percent time spent at idle for
trucks operating in New York City when compared to trucks operating
in other metropolitan areas.
One last point concerning driving cycles should be mentioned.
The average speed for LDVs over the LA-4 is 18.9 mph and, on the urban
dynamometer driving schedule (UDDS), is 19.7 mph. The percent time
spent; at idle is 18.2 percent for both of these cycles. Since SwRI
has indicated that the trucks tested tended to keep up with LDV traf-
£-z over the SARR, the SARR tends to closely approximate the LA-4 and
IDJS. This :s further confirmation that the SARR should result in an
air quality related emission measurement for trucks.
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10
Table 3
Comparison of LDV Operation Data from 5 Cities
Operation N.Y.C. Chicago Cincinnati Houston
Average Speed, 40.5 46.5 54.6 50.3
Freeway, mph
Average Speed, 17.8 21.3 22.4 23.0 23.2
Non-Freeway, mph
Average Speed, 21.6 24.5 25.9 27.7 29.3
Overall, mph
Time, 17.5 14.1 H-3 U-3 10.1
idle
% Total Time, 26.5 30.9 30.7 36.8 34.3
Cruise
% Total Time, 29.1 28.3 30.9 27.4 29.8
Accel
% Total Time, 27.0 26.8 27.0 24.6 25.9
Decel
-1EPA is pursuing the work necessary to develop representative urban
truck driving cycles. In addition, work is ongoing to evaluate the sen-
sitivity of truck emissions to average vehicle speed and to various
cycles at the same average speed. When this work is completed, a minimum
set of air quality related driving cycles will be available. However,
after evaluation of the currently available data, the SARR can be judged
as an acceptable cycle over which to assess air quality related truck
emissions. It is an actual urban cycle and as such, it is superior to
any non-transient cycle. The SARR is the only urban road network over
which actual mass emissions of trucks have been measured.
SwRI has performed emission testing of the same heavy duty gas and
Diesel trucks over the SARR as well as by the appropriate Federal test
procedure. For each truck tested, measurements of grams of pollutant/
pound of fuel are obtained for both the road test and the engine dyna-
mometer test. Degression analysis was performed in order to relate the
emission rate on the dynamometer cycle to the road emission rate. Exami-
nation, of the data indicated that the relationship was linear over the
region where data existed. This assumption was supported by linear
correlation coefficients of .8 or higher. A graphical representation of
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11
the regressions is given in Figures 1 and 2 (pages 12 and 13), for
gas and Diesel trucks respectively. The solid line on each graph
represents the best fit linear regression line. The dotted lines
represent the 90% confidence interval around the mean predicted road
route emissions for a given FTP emission result. The dashed line pre-
sents the case where the FTP emissions equal;the road emissions. Thus,
the more closely the solid line approximates' the dashed line, the
better the emissions measured over the FTP represent emissions measured
during actual urban road operation. The mean of all observations for
each pollutant and powerplant (gas or Diesel) is notated with an x on
each of the graphs.
The SwRI samples of gasoline and Diesel trucks were selected to
approximate the national distribution of trucks with respect to engines
and GVWR. Although it is difficult to accurately stratify such small
samples (the gasoline sample consisted of 25 trucks and the Diesel
sample consisted of 10 trucks), the SwRI samples have the same average
GVWR as the national population: approximately 23,000 pounds GVWR
for gasoline trucks and 56,000 pounds GVWR for Diesel trucks. Addi-
tional variability could be explained for a given size truck by adding
GVWR as an independent variable in the regression equations (thus in-
creasing the correlation and decreasing the width of the confidence
interval). However, the emission estimates which represent the national
population of trucks can be accurately assessed without incorporating
weight as a covariate since the input sample of trucks represents the
national distribution.
From an engineering standpoint, an emission rate of zero on the
dynamometer should result in an emission rate of zero on the road
(unless emissions only result from operation over a mode which is
present in just one of the two tests). However, forcing a linear
regression through the zero-zero point would distort the prediction
in the-region of actual data and the region of greatest interest.
Therefore, in order to accurately fit the data in the region of low
emissions, a higher order curve fit would be required. For the purpose
of this analysis, the linear regression not forced through zero was
considered appropriate since the data appeared linear for emission
rates as low as those being considered for the interim regulations.
The resultant linear regressions are given in Table 4.
Table 5 (page 15) displays the expected percent reduction in urban
road emissions for proposed percent reductions measured by the Federal
test procedures. Table entries are obtained by converting grams/bhp-hr
to grsims/pound of fuel (by using the brake specific fuel consumption)
and using the regression equations from Table 4.
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12
Figure 1
RELATIONSHIPS BETWEEN URBAN AND FTP EMISSIONS FOR GAS TRUCKS
18
HC EMISSIONS
15
E
O)
112
O
i
3 6 9 12 15 18 21
FTP (gm/lb)
21
18
15
E
o>
z 12
i »
3
CO EMISSIONS
300 -
E
a» 200
z
00
oc
100
/'.
.. //
. <*./'
></
/. /
x^ /
^. /
. /
/
X i ,
NO. EMISSIONS
100 200
FTP (gm/lb)
300
8 9 12 15
FTP (gm/lb)
18 21
KEY
BEST FIT LINEAR REGRESSION LINE.
FTP EMISSIONS = URBAN EMISSIONS LINE.
90% CONFIDENCE INTERVAL AROUND
MEAN URBAN VALUE FOR A GIVEN
FTP VALUE.
* SAMPLE MEAN OF ALL OBSERVATIONS.
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13
Figure 2
RELATIONSHIPS BETWEEN URBAN AND FTP EMISSIONS FOR DIESEL TRUCKS
E
O)
E
o>
CD
OC
7.0
5.0
3.0
1 0
. HC EMISSIONS
10 3.0 50 7.0
FTP (gm/lb)
25
20
15
10
30
3 25
o>
CD
CC
20
15
10
CO EMISSIONS
6 9 12 15
FTP (gm/lb)
18
KEY
BEST FIT LINEAR REGRESSION LINE.
FTP EMISSIONS : URBAN EMISSIONS LINE.
90% CONFIDENCE INTERVAL AROUND
MEAN URBAN VALUE FOR A GIVEN
FTP VALUE
x SAMPLE MEAN OF ALL OBSERVATIONS
10 20 30 40 50
FTP (gm/lb)
60
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14
Table 4
Relationship Between SARR Emissions and FTP Emissions (a)
Gas Trucks
HCSARR " 1>33 HCFTP ~ '** r * *81
COSARR e >689 COFTP + 81.1, r - .90
NOxSARR = .591 NOXFTP+ 2.57, r = .91
Diesel Trucks
HCSARR = '769 HCFTP + -861, r = .88
COSARR = 2<11 COpTP ~ 7-28» r » .80
NOxSARR = .271 NOxFTp+ 7.53, r - .89
(a) Emissions expressed in grams/pound of fuel.
Examination of Table 5 indicates that for gasoline trucks, de-
creases in the HC and NOx emissions measured over the FTP accurately
reflect the changes in HC and NOx road emissions which would occur if
more stringent standards were adopted over current observed levels. For
Diesel trucks, the decrease in HC measured over the FTP accurately re- _
fleets the decrease ih~~HC road emissions although this cannot be seen from'
Table 5 since the current range of operation is below the proposed
standards. However, decreases in gasoline truck CO emissions and Diesel
truck CO and NOx emissions measured by the FTP do not result in equiva-
lent reductions of on the road emissions in the region of current emis-
sion performance. Lack of correspondence on the gasoline CO emission
and Diesel NOx emission reductions from 1974 levels can be seen in Table
5. The lack of correlation in Diesel CO emissions cannot be seen in
Table 5 since Diesel vehicles currently are substantially below the
proposed standards. Lack of Diesel CO correlation can be seen in Figure
2.
For gasoline trucks, these conclusions are supported in a study
independent of those discussed above, performed by SwRI. (8) The study
tested eight gasoline engines over the FTP, the UDDS (with modified
accel/decel rates where necessary) and the EPA 23 mode cycles in order
to investigate the reductions in exhaust emission levels attainable
using various control techniques. Evaluation over the 23 mode cycle and
the UDDS assessed the emissions performance of various engines and
control approaches during operation of the engine outside the range of
the current test procedure. The results are shown in Table 6.
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15
Table 5
Expected Percent Reduction in Urban Road Emissions for ^roposed Percent
Reductions Measured by the Current FTP
Percent Reduction from 1974 HDV Standards
Non-Catalyst Technology Catalyst Technology
FTP SARR FTP SARR
HDV HDV
Gas
HC(a) 43 44 71 74
CO 25 8 63 21
NOx(a) 17 13 17 13
HC + NOx 25 27 34 40
Diesel
HC(b)(c)
CO 25 26 63 65
NOx(b) 39 21 39 21
HC + NOx 25 2 34 16
Percent Reduction from Actual 1974 Certification Performance
Non-Catalyst1 Technology Catalyst Technology
FTP SARR FTP SARR
HDV HDV
Gas
HC 38 39 69 71
C0(c) 38 9
NOx 9898
HC + NOx 18 21 29 36
Diesel
HC(c)
C0(c)
NOx 20 9 20 9
HC + NOx 1 13 2
(a) Assume a 1974 standard of HC - 5.22 gms/bhp-hr and NOx - 10.78 gins/
bhp-hr based on sales weighted estimate of the 1974 certification HC/NOx
split. Standards are adjusted for HC measured by FID.
(b) Assume a 1974 standard of HC - 1.2 gms/bhp-hr and NOx =14.8 gms/bhp-
hr based on sales weighted estimate of the 1974 HC/NOx certification soli'
(c) A dash indicates vehicles currently are substantially below 197&
and/or proposed standards - thus comparison of percent reduction mean-
ingless.
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16
Table 6
Percent Reductions in Gasoline Heavy Duty Emissions Measured by the
FTP and over the Modified UDDS
9-Mode FTP UDDS
HC 85 72
CO 90 51
NOx 54 49
Examination of Table 6 supports the results given in Table 5;
that is, the current gasoline FTP overestimates the CO air quality
reductions achieved with a change in control technology. This is pri-
marily caused by the lack of a wide open throttle (full load) opera-
ting mode which is a characteristic mode for urban driving of heavy
duty trucks. Under full load operation, gasoline fueled engines have
a fuel enrichment feature designed to provide optimum power. This has
the side effect of significantly increasing the CO emission rate.
- The fact that changes in NOx emissions measured by the 13 mode FTP
do not correspond with equivalent changes measured over the SARR for
Diesel engines can also be explained. In general, Diesel trucks emit
considerably more oxides of nitrogen under the 13-mode test than when
driven over the SARR. This follows when the type of driving represented
by the urban traffic route is compared to the intent of the 13-mode
test. In the 13-mode test, the idle mode is given a 20 percent weighting
factor and each of the remaining speed and load points an equal 8 per-
cent weighting factor. Thus, the 13-mode test gives the same weight to
100 and 75 percent load as it does to zero and 25 percent load. That
is, the 13-mode test was developed so as to reflect all types of HD
Diesel vehicle operation, both urban and inter-city. The SARR, in
contrast, is not a high load factor test since the road course did
not stress the vehicle in the way sustained high-speed, high-power
inter-city highway driving does. However, it better estimates the
emission factors which result when large Diesel trucks operate in and
around urban areas.
Test procedure variability and absolute level of emissions explain
why CO emissions measured by th 13-mode FTP do not correspond with equi-
valent changes measured over the SARR for Diesel engines. CO emissions
from Diesel are very low and the measurement of these emissions using
current instrumentation is extremely variable. Therefore, the actual
correlation between FTP and road emissions for Diesel CO is less than
any of the other five correlations while the variation in the road route
emission levels is considerably greater. These two effects combine to
prevent accurate road route predictions from FTP predictions.
-------
17
In conclusion, the air quality benefits attributed to various
control strategies will be computed using the air quality related HDV
emissions. Thus, standard changes for gasoline truck CO and Diesel
truck CO and NOx will not result in equally large air quality improve-
ments .
C. Gasoline Test Cycle Improvements
The problem of specifying gasoline engine load points in terms of
manifold vacuum was evaluated in a separate technical report. (9) The
report redefines the "9-mode" test points in terms of percent of maximum
torque as opposed to manifold vacuum. Torque points were derived from
regression analysis of 19 heavy duty gasoline engines. Table 7 lists
the current manifold vacuum levels, derived percent torque levels, and
range observed among the 19 engines.
Table 7
Manifold Vacuum and Corresponding Load Levels
« J (a)
Modev '
5
2, A, 6, 8
3
7
Manifold
Vacuum
19 (in Hg.)
16 (in Hg.)
10 (in Hg.)
3 (in Hg.)
% Observed
Torque
10
25
55
90
Range
% Torque
19 Engines
5-18
22-32
51-65
78-100
Modes 1 and 9 are idle and closed throttle respectively.
-The fact that a substantial variation in torque exists for a given
level of manifold vacuum suggests that some engines tested by the
modified procedure may have different emission results although or the
average, emission levels monitored by the two methods will be the same.
Fortunately, gasoline engine emissions are highly sensitive to load
variation only near no load and full load operation. Data gathered on
eight engines were presented in the report (9) to verify this f^ct. The
expected impact of a change in test points from manifold vacuum to
percent load on an individual manufacturer is minor because the no load
and near full load emission rates are functions of relatively minor
carburetor recalibrations. Near no load, carburetor calibration is
affected by "idle" and off idle" fuel rates which are easily adjusted by
changing fuel and air bleed openings.- Near full load, the adjustment of
the "power valve" calibration is usually a change in spring tension on
the valve slide.
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18
D. Instrumentation Problems and Improvements
The sampling system and instrumentation associated with current
test procedures have several deficiencies. These include measurement of
NO only by NDIR when standards are specified for NOx. Additionally,
chemical driers are used such that some effect on conversion of N0~ to
NO has been identified. On the gasoline "9-mode" analysis system, HC is
measured by NDIR and then adjusted by a constant which was determined to
be the relationship between NDIR respor.se and total hydrocarbon measure-
ment using an FID. FID is currently specified for analysis of HC on all
other mobile source emission test procedures. The NDIR instrument has
severe limitations in accuracy when measuring low concentration levels.
Raw concentrations of undiluted exhaust are measured at ambient conditions
which results in condensation of water as well as heavy hydrocarbons
within sample handling and instrumentation.
An extensive problem analysis and development program aimed at
solving the majority of these instrumentation problems was conducted.
The effort, recently completed, is documented in two technical reports.
(10) (11).
The first of these technical reports (10) describes a completely
redesigned sample handling and analysis system. The schematic diagram
for the system hardware is shown in Figure 3 (page 19). The major
changes include: substitution of chemiluminescence analyzers for NDIR
to allow measurement of total NOx at low concentration levels; the NDIR
hydrocarbon instrument is replaced by FID for gasoline engines to allow
accurate "total" hydrocarbon measurement at low concentrations; the
need for chemical driers and the problems of hydrocarbon "hang-up" and
water condensation have been eliminated by a high bypass ratio heated
sample line and ice bath incorporated between the N0? to NO thermal
converter and the reaction chamber.
This redesigned system is expected to significantly improve the
accuracy of heavy duty engine emission measurement especially at low
concentration levels while simultaneously reducing maintenance problems.
The second technical report (11) examines the net impact of the
proposed measurement changes on the level of emissions measured and
proposes correction factors to be applied to current standards or pro-
posed standards if based on existing sampling methods. Data from
several sources including EPA, Southwest Research Institute, TRW Systems,
Scott Research and others were analyzed. The relationships are shown in
equations (1) and (2) below:
(1) NOx (CHEM) - NO (NDIR) x (.9 to 1.0) , ,
(2) HC (FID) = HC (NDIR) x (1.27 to 1.42) w
(a)
Includes current test procedure ratio of 1.8.
-------
19
E. Existing Standards
Standards for the 1975 model year are 16 gm/BH?-HR HC + NOx and 40
gm/BHP-HR CO in 49 states. California standards are 10 gm/BHP-HR HC +
NOx and 30 gm/BHP-HR CO using identical test procedures except for the
lack of a durability requirement on Diesel engines. Additionally, smoke
standards determined by federal procedures for 50 states are 20% accel,
15% lug down, and 50% peak opacity. California also has an evaporative
HC standard of 2 gm/test.
The specification of heavy duty gaseous emission standards in
units of grams/brake horsepowerhour takes into account the degree of
useful work performed by the class of vehicles into which these engines
are built. That is, the level of pollutants in terms of mass allowable
is directly proportional to the energy output from the engine.
Common numerical standards have been specified for both gas
and Diesel engines even though there is a substantial difference in
the test procedure which introduces uncertainty about the real degree
of equivalency which exists. No data other than those already presented
in this section are available to determine equivalency of the two pro-
cedures. It is difficult to run gasoline engines by 13 mode procedures
or Diesel engines by 9-mode procedure because of the differences in load
parameter control and instrumentation. The long term objective is, of
course, to have common or at least equitable procedures. However, in the
interim it will be necessary to assume equivalence lacking definitive
data.
Assuming equivalence in procedure there is no basis for having
separate gas and Diesel standards since both engine types provide the
same function in commercial service. The two engine types are in com-
petition and the factors which govern the choice of one powerplant
over another include:
1. First cost - The Diesel engine is approximately 3 times
the cost of an equivalent capacity gasoline powerplant.
2. Operating economy - The Diesel engine enjoys approximately
25% better fuel economy when operated in the same size truck.
3. Maintenance - Diesel engines typically operate 200-250,000
miles between major overhauls. This is twice the interval
for gasoline engines.
Commercial truck managers carefully evaluate the economic factors
before choosing a powerplant. It is extremely doubtful that emission
performance plays any role in their decisions.
-------
Figure 3
ftpan and Span and
Zero Oatai Zaro Oaiet
legend
Perticulete Fill..,
" Back; rtuura AtgulttQf with
Internal Control Loop Ih= i
"~~T^^y Lm« Pf«ssur* Regulator will
£~^ Internal Contte' Loop Show
II Valv* or Equivalent
(Dftrktnd Lag Indicaltt Common **o>-1
Flaw Control or Needle Valve
-------
21 .
From the environmental viewpoint there is little incentive to
provide separate standards for each type of power plant since such a
strategy would likely give economic advantage to the "dirty" powerplant
(for HC and CO the gasoline fueled engine and for NOx the Diesel).
Assuming both were controlled to technologically feasible limits of the
Diesel with standards set a such a level, the gasoline engine could be
ruled out of the marketplace. Likewise if standards based on maximum
feasible control for gasoline NOx emissions were set, the Diesel engine
may not be able to comply. A more rational approach seems to be to
define the need for additional control and the technologically feasible
limits for both powerplants, then set a common standard representing
strict control of the "dirtiest" source and let economic advantages of
each dictate their continued use.
The combination of NOx and HC standards into a single requirement
was first proposed by the State of California and adopted with issuance
of the 1973 California standards. The approach was adopted by EPA the
following year. The California Air Resources Board position stemmed
from their belief that oxidant formation could be controlled by reductions
in HC or NOx. Most recent research suggests that reductions in hydro-
carbons are the most effective means of controlling oxidant formation.
In addition, the agency has determined that control of NOx should be
based solely on the need to meet ambient air quality N0~ standards. (12)
Thus, there is little justification for continuing the practice of
combining HC and NOx as a single standard. Separating the two con-
stituents and setting separate standards now posts a problems, however,
in that manufacturers have been trading off control of HC for NOx and
vice-versa in order to optimize performance and economy. Therefore,
some manufacturers have relatively high NOx and others high HC. The
extent to which this occurs is treated in the technology assessment.
Based on input from the National Air Data Branch of EPA (12),
control of hydrocarbon emissions is first priority since many regions in
the US have an oxidant problem and the problem is more widespread than
previously estimated. Taking these facts into account along with the
existing tradeoff situation of HC and NOx, there are several options to
stating future standards.
1. Set an HC standard and NOx standard separately.
2. Set an HC standard and a maximum HC + NOx standard.
3. Set standards for HC and NOx separately and a third combined
HC + NOx standard at a lower total level.
Option 1 is desirable but does not satisfy the problem of past tradeoffs
and could therefore result in wasted development and possible elimination
of engines with unbalanced levels of either constituent. Option 2 places
iii^ortance on control of HC, allows those who have traded off NOx control
for HC to continue development along such lines, and peanlizes those who
have traded off HC control for NOx control. Option 3 treats both con-
sui.tueiits with equal importance, yet would force those who have
obtained a hi/ii degree of control for either constitutent to maintain
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22
Option 1, totally independent and separate standards, should be
\c long tc:rm goal and will be proposed with adoption of advanced urban
operation based test procedures. However, taking into account the facts
that control of NOx by existing procedures results in much smaller gains
in urban emissions reductions (see Table 5) and recognizing the need to
concentrate efforts on HC control which is well predicted by current
procedures, option 2 is more appropriate for an interim control strategy.
Option 3 would overemphasize control of NOx considering current uncer-
tainties about NOx ambient air quality.
-> ,
F. Summary & Conclusions
There are threa separate test procedures applied to heavy duty
engine emissions measurement. These are the "13 mode" and transient
smoke test procedures for Diesel engines, and the "9-mode" test pro-
cedure for gasoline engines. These procedures have several deficiencies
whxcn have been examined in terms of possible limitations on their use-
fulness for estimating urban emissions, and relationships have been
developed to quantify current capabilities. In addition, numerous in-
strumentation and measurement problems have been addressed through a
redesign of the sampling and analytical systems.
Both the 9 and 13 mode tests are good statistical predictors of
urban HC and NOx emissions. Also, the 9-mode is a good statistical
predictor of urban CO emissions whereas the 13 mode is not. The problem
with both procedures is that for CO and NOx there is poor correspondence,
i.e., equivalent percent reductions are not attainable. In the short
term, with not too stringent standards, significant reductions in
absolute levels are possible, but at more stringent standard levels, no
additional control may be obtainable.
Test procedure improvements include the substitution of percent
load for manifold vacuum as a reference point in the "9-mode" test,
substitution of chemiluminescence and FID analyzers for gasoline HC and
all NOx measurements, as well as development of a high flow rate heated
sampling scheme to eliminate condensation and delay problems. These
modifications if adopted will sufficiently improve test procedures to
allow reasonable confidence in measuring emission rates.
The issues of separate gas and Diesel standards and separate HC and
NOx standards were examined. There is no reasonable basis for having a
unique standard for each powerplant design. Neither is there continuing
justification for combining HC and NOx as a single standard other than
the fact that manufacturers may be able to achieve a higher level of
control without loss in marketability of their complete product lines if
standards are specified in terms of EC, and. HC plus NOx.
-------
23
IV . Technology Assessment
The capability of heavy duty e'ngine manufacturers to produce engines
laving lower emission levels was examined as a separate project within
EPA. Experimental work was conducted under contract to Southwest Research
Institute and the Bureau of Mines on several engines to identify the
lowest levels of emissions achievable. In addition, meetings were held
with all the major manufacturers to determine the level of technology
each has developed, expected fuel penalties associated with various
standards, and lead times for various control hardware. Finally, in-
house data and manufacturers' data were analyzed to determine current
emission performance and fuel consumption rates.
A separate report of the technology assessment panel (K. Hellman
and R. Wagner, et. al.) was prepared (13). The information presented
herein is limited to the key elements of the panel's efforts. This
information included a summary of then current emission performance,
analysis of control techniques that could be used to meet various emis-
sion levels, fuel penalties and costs. After the preparation of the
technology panel report, further information was obtained from manu-
facturers as a result of hearings held in connection with California's
consideration of adopting several alternative heavy duty standards. A
summary of these findings is also included. Finally, summary and con-
clusions of the overall technology report are presented.
A. Current Heavy Duty Emission Performance
The status, of current Heavy Duty engines as far as emission per-
formance is concerned, falls into the same two classes as the two engine
types, Diesel engines and gasoline engines.
Current Diesel engines exhibit gaseous emissions performance not
too much different from uncontrolled Diesel engines. The advances that
have been made in Diesel emission control have been primarily in the
area of smoke emissions. Substantial reductions in smoke have been made.
Current gasoline emission levels show substantial reductions in
HC and CO emissions compared to uncontrolled gasoline engines. NOx
levels of current gasoline engines are higher than those of uncontrolled
gasoline engines. In general, although reductions have been made in
gasoline engine HC and CO emissions, these current values are still not
as low as those from current Diesel engines.
T.ie current and uncontrolled levels for Heavy Duty engines as
r/iciLurid by the HDV FTP are shown in Table 8. Also in Table 8 are
dhowvi uhe future California requirements. All percent reductions are
baiiic. or. riDV FTP measurements and are not necessarily percent reduc-
tions in urban emissions as discussed in Section III.
B. Control Technology for Heavy Duty Engines
I. HC Control Techniques
-------
24
Diesel Engines
The HC control techniques available for Diesel engines are primarily
those that involve modification of the combustion process. These combus-
tion process modifications are generally obtained by changing the fuel
injection timing and/or rate, improving the fuel injector design, chang-
ing the air motion in the cylinder during combustion, changing the combus-
tion chamber design, and changing the amount of air available for HC
oxidation, for example, by turbocharging. Of these methods, the approach
considered most attractive, strictly as an HC control technique, ,is the
approach of improving the fuel injection system. The need for more
sophisticated fuel injection systems is apparent to most manufacturers,
and some have had active programs to develop improved systems underway
for some time. Improved fuel injection systems are an attractive route
to improved HC control, since the improvements in the combustion process
obtained may well have beneficial effects in other areas; BSFC and smoke,
for example.
Another approach toward control of HC emissions from Diesels is the
control of crankcase emissions. Currently no requirement exists for
Diesel crankcase control. Control of this type of HC emission is Well-
known, being the positive crankcase ventilation (PCV) valve which has
been used on passenger car engines for many years. Although some work
will have to be done to adapt the approach to turbocharged engines,
control of crankcase emissions from Diesels is feasible. However, there
is a need to qualify and quantify Diesel crankcase emissions before
adopting'a regulation.
Gasoline Engines
The HC control techniques available for gasoline engines parallel
those for gasoline LDV. Basically, these techniques include: a) im-
proved air/fuel management, b) changes to the combustion chamber to
reduce the surface to volume ratio, c) spark timing retarded away from
MBT, d) air injection, e) thermal reactors (both rich and lean), and
f) oxidation catalysts.
Of the above control techniques, improved air/fuel management, air
injection and oxidation catalysts are the most attractive control
techniques. The combustion chamber modifications, the spark retard and
the thermal reactors were judged not as attractive basically because
some of them (spark retard, rich thermal reactors) may have deleterious
effects on fuel consumption. The combustion chamber modifications and
lean thermal reactors were also considered not as attractive because,
for most manufacturers, the gasoline engines are essentially derivations
of passenger car engines and the trend in the passenger car engine
design appears to be toward combustion chambers with more mechanical
octane which tend to have higher surface-to-volume ratios and also
toward use of catalytic converters as opposed to lean thermal reactors.
2. CO Control Techniques
sel Engiu.es
-------
.1977 California Table 8
optional standard
Summary Chart - Heavy Duty Emissions
FID Yvf -u"COIltrolle<1 .Uncontrolled Gasoline Avg.
(Pf Diesel Avg.
tu: 5 6 I 1 ** * *
(Sin/Blll'-hl-) | " 2 3 4
74 Diesel Avg.
Uiiconl rolled
CO »ie«ol Avtj.
(i-ni/KilP-hr^ ltT*l !"\\
io 20
1 '74 Diesel Avg. ' '74
NOx
(Rin/WIP-ht) ^ 2
HONOx
(gm/nilP-l,r) ( '2 '3 ^
Visible
Sraoke Limit
10
'74 Lug
Average
TC
"7A Gasoline Avg.
J'77 California Std
.'75 California Std
| 1 | '74 Standard
rli 1 i i i
15 20
Uncontrolled Gasoline Avg. «
1 ! 1 1 1 ^l 1
30 40 50 60 70 80 90 100 110 120 130 140
Gasoline Avg.
.Uncontrolled 1977 California Uncontrolled
[Gasoline Avg. | optional standard [ousel AVB.
\7' tj/y
3 4 5 6 7
75 Calif ornta Std
77 California Std
/T\ fTl
(I) ULJ
5 10
'74 Lug '74 Accel
Standard Standard
?trt: f i
''74 Accel 'Uncontrolled Uncontrolled
Average Lug Average Accel Average
. L . . .. i . fSi .1 B PI i I
- 1 --(A» ' 1» D
8 9 10 1 11 W 13
Uncon- .Uncon- line Avg. Avg.
trolled jtrolled
[piesel Avg. JGasoline Avg.
f H_J 15 20
' [-'74 Diesel Avg. '74 Standard
' '74 Gasoline Avg.
'74 Peak
Standard
i A l~l I
40 50 60
Uncontrolled
Peak Average
»74 Peak
Average
-------
26
The low CO emissions from Diesel engines are primarily a function
of the lean air/fuel ratio characteristic of Diesel combustion.
Techniques that supply more air or better combustion chamber mixing, will
lower CO emissions, although there is currently no concerted effort in
the Diesel engine field to lower CO emissions, since they are already
so low.
Gasoline Engines
Control techniques for CO from gasoline engines are much the same as
those for HC emissions, namely, improved air/fuel management (including
lean air/fuel ratio operation), air injection, thermal reactors and oxida-
tion catalysts. As is the case with HC control techniques, the most
attractive approaches involve improved air/fuel management, air Injection,
and oxidation catalysts.
The change in gasoline engine test procedure from manifold vacuum
to percent power is expected to have greatest impact on CO control. Manu-
facturers will have basically two options: to set the power enrichment
to come in at power levels greater than 90 percent power, if possible,
or to design the emission control system to be able to handle the amount
of power enrichment that occurs during the test. The first approach,
setting the power enrichment in such a way that it is not in operation
during the test, may be difficult to do since the percent increase when
power enrichment is used is typically greater than 10 percent. Since the
first approach involves relatively less effort than the second, the panel
considers it likely that some manufacturers may choose to derate their
engines in such a manner as to not have the power enrichment occur during
the cycle. The possibilities for "false derating", i.e., derating to get
by the test with the engine actually producing more power than the manu-
facturer claims to EPA, is an area that must be considered closely in the
certification/enforcement process. A true derating could have beneficial
effects on gasoline truck fuel consumption. This is the case if one com-
pares the likely fuel consumption performance of two gasoline engines
that produce the same power, one engine (smaller in displacement) operat-
ing under power enrichment and the other (larger engine) operating
without power enrichment.
3. NOx Control Techniques
Diesel Engines
The techniques available for the control of NOx from Diesel
engines are injection timing changes, injection system improvements,
catering of the combustion process by combustion chamber design, and
addition of a diluent to the air/fuel mixture.
Exauples of modifications to the combustion chamber are the
changing of the air motion ("swirl" and "squish") during combustion and
changing the physical characteristics of the chamber from the common
opc.i chamber> direct injection type to one that is more complicated in
oV-tra, such a.3 a. aivr.ded chamber ("swirl camber" or "prechamber), a
con.: ini-i^GYi of i/;ie -wo ("poker head"), or a modified bowl type ("squish
-------
27
>
*.*
Two main diluents have been studied for use in Diesel engines. These
are water injection and EGR.
The use of improved injection systems and EGR are believed to be the
approaches that will yield the best results in the short term. The use of
water injection is not considered to be practical. Changes to different
combustion chamber configurations on a widespread basis were not con-
sidered to be achievable in the short term because of lead time and
industry attitudes toward combustion chambers. It appears that each manu-
facturer, in general, has his own preferred type of combustion chamber de-
sign, which he is somewhat reluctant to change. This attitude coupled
with the common wisdom that the combustion chambers with low NOx cap-
ability (for example, the prechamber) have higher fuel consumption, has
also buttressed the reluctance to change. Even some manufacturers who
currently make indirect injection-engines are considering changing to
direct injection engines in the hopes of improved fuel consumption. How-
ever, the common wisdom concerning the direct versus indirect injection
engines may not be correct, since the comparisons are rarely made at the
same NOx emission level, possibly leading to mistaken approaches by some
manufacturers.
The Diesel industry also seems somewhat reluctant to use the EGR
approach. Most of the arguments against EGR are not technically
valid, but are reflections of uncertainty based on the inexperience of
the industry with actual field experience on EGR-equipped trucks. The
major technical problem with EGR on Diesels is the proper management and
control of the amount of EGR, because a poorly designed system may result
in excessive smoke emissions.
-------
28
Gasoline Engines
Although EGR is also applicable to gasoline engines and is an
effective control technique, other methods are applicable to gasoline
engines for NOx control. Spark retard is an effective technique, but
massive retard was ruled out as a primary NOx control technique due to
its effect on fuel consumption. Besides EGR and spark retard, the use
of NOx catalysts is possible on gasoline engines. Recent developments
in the area of metallic NOx catalysts show much promise for application
in the automotive area and this technology is transferable to the Heavy
Duty gasoline engine application. However, because of the time frame of
the LDV statutory NOx standards that will require use of NOx catalysts
(1978), it is likely that use of NOx catalysts on Heavy Duty gasoline
engines will lag this 1978 date by enough to put it out of the time
frame of this study. Therefore the use of an EGR system of the "super"
proportional type was considered to be the most attractive NOx control
technique for gasoline engines.
4. Smoke Control Techniques
For Diesel engines the smoke control techniques involve approaches
that reduce smoke under two general operating conditions, steady state
modes and transient modes. The control of steady state smoke is achieved
by reducing or eliminating any pockets of unburned fuel in the cylinder
near the end of the combustion process, by changing the fuel injection
system, and by improving air/fuel mixing. Turbocharging can help smoke
control in steady state conditions because more air is provided to
promote complete combustion. Additionally turbocharged engines can be
calibrated under steady state conditions to be leaner overall than
naturally aspirated engines, yet deliver more power since they are
boosted. Transient smoke is controlled by limiting the fuel available
during a transient, for example during vehicle acceleration. Without
control over the fuel, initially there would be too much fuel and
excessive smoke would result. This problem is even more severe with
turbocharged engines since the maximum fuel rate is based on the amount
of air provided by the turbocharger and at low speed the turbocharger
cannot provide all the air that it can when it is up to speed. Accord-
ing to the industry, the technique of limiting the fuel on initial
acceleration may have two drawbacks in field use. First, without
changing the transmission, a vehicle may not be able to climb out of the
sub-surface loading ramps common in many areas. Secondly, drastic
limitations on the initial fuel rate may encourage tampering in the
field if the drivers feel that their vehicles are significantly down on
acceleration power compared to vehicles without the tight controls.
Because there was no firm evidence available to indicate that
current 1974 levels of Diesel smoke are objectionable, no further re-
ductions in Diesel smoke were considered. However, the lowering of the
sucjadards to current levels of control to prevent manufacturers from
-icrtasing, smoke emissions through trade-offs is proposed.
-------
29
:>. Emissions and Noise
Much has been said about the "tradeoff" between emission control
and noise control, usually via the "increased retard, more cooling,
higher fan speed, more noise" argument. There is not necessarily any
tradeoff between emissions and noise control for heavy duty vehicles.
The noise aspects of any vehicle/engine package will have to be
optimized in the future, along with the emissions, and control tech-
niques for noise will have to be implemented. It is possible that the
noise control system may be different for engines meeting,different
emission levels, but this does not mean that there is some tradeoff and
one has to give up emission control to get noise control or vice versa.
It just means that the overall engine/vehicle system to control both
noise and emissions may be different from those designed to control just
noise or just emissions. The more frank members of the Diesel industry
have indicated as much.
C. Industry Capability at Various Emission Levels
The report team began this study, not by considering specific
emission levels per se', but by considering the answers to the
following questions:
1. What emission standards will result in the least penalty
in BSFC?
2. What emission standards represent the maximum control of
HC emissions feasible in the timeframe considered?
3. What is the current industry-wide capability to meet the
1977 California Heavy Duty standards?
4. What emission standards will be achievable by gasoline
engines using oxidation catalysts?
1. Techniques for Minimum Fuel Economy Loss
As discussed earlier, techniques applicable to the control of HC
and NOx emissions can have the most important influence on BSFC, for
a given engine system. At levels of HC and NOx emissions below the
current requirements, the fuel consumption change depends to a great
extent: on what control systems are used to meet the lower levels. The
use of injection or spark retard will involve fuel consumption penalties
over current BSFC values, for both Diesel and gasoline engines. However,
the use of more sophisticated technology than just simple retard can
reduce or eliminate these potential losses. Since most of the data
and development effort have been expanded toward control of NOx emissions,
?.Cx level was used as the indicator for determining the BSFC impact.
The report team concludts that a NOx level of 9 gm/BHP-HR can be met
irich no significant increase in BSFC. This NOx level will probably require
-------
30
development of more sophisticated technology than exists on current
heavy duty engines. Although there is enough time for the develop-
ment of this improved technology, manufacturers can also meet our
9 gram/BHP-HR level by recalibrating current engines, if their
development programs are not successful, and/or they vi."."1 accept
the fuel consumption penalties of approximately 4 percent iht''. Tiiy
result if no further development work is done.
The fuel consumption impact of any degree of emission control is a.
subject of much interest. The industry estimates of these potential
losses varies widely as shown in Figure 4 (page 31). The estimates of Cater-
pillar, Cummins, and General Motors reflect recent development efforts
whereas those of Chrysler, Ford, and International Harvester represent
much older development work presented to the CARS in 1973. The gross
overestimations of fuel penalty by Chrysler, Ford, and IH as compared
to the others clearly represent a lack of development effort by these
manufacturers in the opinion of the report team. Furthermore, the
report team concludes that the large fuel consumption "penalties"
quoted by some manufacturers are more the result of questionable data
chosen to try to influence CARS's decision on their standards than they
are estimates representative of good faith efforts to achieve the
emission levels required with minimum or no BSFC penalty.
2. Maximum Control of HC Emissions
Maximum control of HC emissions primarily involves investigation
of the HC control capability of the gasoline engine, since the Diesels
are already so low. The report team estimates that a HC level of
3.0 gm/BHP-HR is close to the lowest level that can be achieved by
most gasoline engines without catalysts, although advanced air in-
jection systems, such as modulated air injection systems, with suf-
ficient air flow capability, may be able to achieve lower levels.
If gasoline engines use catalytic control of HC, levels of 1.5 gm/BHP-
HR are possible, allowing for a conservative (i.e. large) catalyst HC
efficiency reduction on durability. Diesel engines also have the
capability to meet the 1.5 gm/BHP-HR level.
3. California 1977 Standards
The 1977 California standards of 5 (HC+NOx) and 25 (CO) determired
by California's certification procedure are approximately equal to
1 (HC)/25 (CO)/5 (NOx) on a Federal basis. This level of control
can be demonstrated in California by 1977, but the report team
estimates that this will involve fuel consumption penalties of
3 percent for Diesel engines and 7 percent for gasoline engines,
at a minimum, compared to 1974. In the opinion of the report team,
the Heavy Duty industry will not have the capability to produce at a
full range (comparable to the 1974 lines) of engines nationwide that
meet the 1 (HC)/25 (CO)/5 (NOx) levels until after 1978. Since the
-------
Estimated Percent Increase in Fuel Consumption
10
O
Caterpillar-Diesel
Chrysler-Gasoline
Cummins-Diesel
Ford-Gasoline
CM-Dit'sel
CM-Gnsoline
IH-Diesel
Ili Gasoline
o
-I
*»
O
D
9
rfl
n
n
C -1
fl> (D
0) O
rt 3
V)
n c
01 s
|-i XI
h1- rt
o1 o"
^ 9
I* M
l>> m
S
W 6)
S rt
O H-
+ re
'S, Ul
o
X M
^ B)
^ rt
IsJ t*
to 0
(U
/-s rl
O It
O o.
IU
1-1
D.
1
re
-------
32
time f rane considered in this report does cot include the post-1978
time frame, meeting the "California" levels of 1 (EC)/25 (CO>/5 (H)x)
was not considered feasible, because :'.n tV.s tir.e frami 'T.r78) riarket
demand may not be met. Consideration of «nr'.s,?r.c.- ".ev??.e like the
1 (HC)/25 (CO)/5 (NOx) should be re-examined by Z?A -*hc?. -he iiev
heavy duty test procedures, now under development, are promulgated.
This additional lead time will also give the ranu^acturers tr'-try*. to
optimize and improve their systems, and cour>led with *.he practical
experience from field use in California, systems superior to those
now planned for California in 1977 could be available on a national
basis in the post-1978 time frame, if air quality considerations
require their use.
4. Gasoline Engines with Oxidation Catalysts
As the requirements for HC and CO emissions are reduced, the use of
oxidation catalysts for Heavy Duty gasoline engines becomes more
necessary. For most gasoline engines it has been estimated that
HC levels below the 2 to 3 level will require the use of catalysts.
CO levels below the 18 to 20 range will also be met most-easily by
use of catalysts.
D. Development Required to Meet Future Standards
Meeting the standards of 3.0 (HC)/30 (C0)/9.0 (NOx) or 1.5 (HC)/
15 (C0)/9.0 (NOx) considered in this report will require development
work to avoid the occurance of fuel consumption penalties. Generally
speaking, these development programs are underway now, but they
must be focused toward these potential standards.
The programs underway to meet the 1977 California standards, for Heavy
Duty engines will provide the basis for most of the work necessary
to meet the standards discussed in this report.
Listed in Table 9 (page 33) are estimates of where the development
effort could be concentrated to effectively meet the standards.
E. Control Technology - Summary
Listed in table 10 are estimates of the ranges in gaseous amirsions
over which different types of control techniques could be used. The .
applicable range is shown for each control technique. Some control techniques
overlap others since each type of technical approach has somewhat different
effects on different engines. The values for the 1974 certification results
are indicated by the square-ended bars and the estimates for various control
techniques are shown with slant-ended bars. Although the 1974 certification
results are not adjusted for test procedure differences, other estimates are.
-------
33
Table 9
Development Effort to Meet
Possible 'future H-D Emission Standards
Engine Type
Pollutant
HC
Gasoline H-D Engine
CO
NOX
Ei-oc.r.aed work in the area
of air/fuel management, air
injection systems. Serious
development work required
on oxidation catalysts for
the 1.5 HC level. Work on
developing positive fuel
shut off during decelera-
tions should be expanded.
Expanded work in the area
of power enrichment versus
engine size tradeoffs.
More work on air/fuel manage-
ment and air injection.
Serious development work
required on oxidation
catalysts for the 15 CO
level.
More development work needed
on optimizing EGR rate and
control and engine calibra-
tions with EGR. Close
monitoring of NOx catalyst
development in LDV area.
Diesel H-D Engine
Expanded effort in the area
of improved fuel injection
systems.
Only work needed is monitoring
of levels to ensure that CO
problems do not occur.
Smoke
Serious effort on EGR systems
and EGR control and engine
optimization with EGR required.
More work required on direct
injection versus indirect
injection engines as a function
of NOx level.
Development effort required to
produce advanced turbochargers
that are more controllable.
Evaluations of superchargers
with superior transient re-
sponse should be expanded.
-------
Table 10A
Summary Chart Heavy Duty uc Control Technology
Ranges for Various Control Techniques
«x-**Ar)".incril r.I.^ysr'WNs
^s^~
\ Since of J974 Cert Rcsu
., 1Q7/. Pic
" - r\
^X^Altt + QX. vatalygfc^
_^^ AIK + 1)11 +
_^-*-- "
^-^
|
Hydrocarbons,
IIC, CH/B11P-IIR
0 1
,
Improved Inlcctors ^^
ts-Dlcscl
cl Average
Improved Fuel HctorlnB^*-^
AIR plus Dcccll Modulator.
""""^ AIR Inlcction.
*2 3
D
I
1 E
S
E
L
,
C
A
S
0
(OH) ^^ L
I
(AIM "^-^ N
E
Range of 197A Cert Results - Gasoline |
u 1974 Gasoline Average
1
i i - * i t i
4 5 67o
Possible
Standard
-------
Table 10D
SucL-ary Chart-Heavy Duty CO Control Technology
Ranges for Various Control Tec' ?.!<;. re
..-. nc;c4 F.I^systcmaV^
IK-IDLC of 1974 Cert Results-Diesel
y 1974 Diesel Average
/I
/* AIU + OX catalyst \
^-*^"AIR + iii
^^
\ "'
Carbon Monoxide,
CO, CM/BHP-HR
.
>rovcd MeterinR "^^v.
Air Injection. (AIR) ^N^
Range of 1974 Cert Results - Gasoline
" y 1974 Gasoline Av
0 S "lO 15 2D 25 3
D
I
E
S
E
L
C
._._.._._
S
0
L
I
V
E
1
;ragc
0 '
w
Possible
Standard
Possible
Standard
-------
Table IOC
Summary Chart-Heavy Duty NOx Control Technology
Ranges for Various Control Techniques
Proportional ECU Systems
1 1 1974 Indirect Inlectlo
1 Ranee of 1
^^NOx Catalyst "\^
^«*^*^Proportlonal ECR Systems ""v<»^.
1 Range of 1974 Cert Rcsul
* *
J
Oxlucs of Nitrogen,
NOx, CM/BIIP-HR
D
i (ID!) Enclnes
t
S
>74 Cert Results-Diesel ] E
L
w 1Q74 Dlcael Avernap
G
A
S
0
L """"
I
:s-Gasoline | N
E
» 1974 Rasoline Avcrnce
01 2 3 4 ' 5* 6 7 8 9 I'D 11 12 13 ' 14 ' IS
\o
«*»
Possible
Standard
-------
37
F. Evaporative HC Control
Heavy duty gasoline fueled vehicles are not currently covered V/
any evaporative hydrocarbon standard, except in California where thsy
must meet the light duty standard of 2 grams/test. California
specifies the Federal light duty test procedure, but certifies the
system by design evaluation rather than requiring confirmatory tfstinp
of completed vehicles. EPA has conducted limited tests on heavy duty
vehicles using the enclosure, or SHED, technique. These data, sum-
marized and compared to LDV standards in Table 11, show that HDV
gasoline fueled vehicles are a significant source of evaporative HC
emissions, even when controlled to the current California standard.
Table 11
Preliminary HDV Evaporative Emission Data
Total SHED Evaporative Equivalent HC
Vehicle Description Loss gms/test gms/mi.
1. HDV Gasoline (uncontrolled) 30 2.8
2. HDV Gasoline (Calif, controls) 18 1.5
3. HDV Diesel (uncontrolled) 2 0.1
4. LDV (1978 statutory exhaust std.) - 0.41
5. LDV (1979 Proposed Evap. std.) 2 0.2
The experimental data obtained on a large Diesel powered tractor with
multiple fuel tanks show this uncontrolled vehicle had evaporative losses
below 2 gms/test primarily because of the low volatility of Diesel fuel
coupled with the "sealed" nature of the Diesel fuel injection system. The
data suggest that no evaporative standard would be required for Diesel
heavy duty vehicles unless gasoline fueled vehicles were required tc go
below 2 gms/test or in the event of multi-fuel engines or use of broad
distillate fuels.
It is probably feasible to control gasoline fueled HDVs to near the
levels of a controlled LDV. This is because of the two primary sources
of evaporative loss: carburetor and fuel tank. The carburetor design
and environment for an HDV is not significantly different than for an
LDV. Further, fuel tank (diurnal) losses may be much greater as a
result of large volume and multiple fuel tanks. However, control by
carbon canister absorption can be effected by increasing the volume of
the storage device or using multiple devices.
The specific hardware employed in such a low emission evr.po-?t '.v:
control system includes a carbon vapor storage canister, fuel ta'il-. vrror
-------
38
liquid separator, modified carburetor with -.rarped venting, anc. miscel-
laneous hoses and tubing to connect .the several components. The cost
of such a control system applied to light du"y vehicles is aoprox'inately
$15 per car. For heavy duty vehicles, EPA estimates the per vehicle
cost of an effective control system capable of meeting the 2 j^n/tcst
standard at $25. This higher amount accounts for the larger canister
and additional plumbing of multiple fuel tanks when applied.
The tradeoffs associated with evaporative control includes (in
addition to the higher first cost) , a slight weight penalty estimated
at 10 Ibs., and possible increases in exhaust hydrocarbon and carbon
monoxide emissions if the storage media is purged rapidly and in a mode
of relatively poor combustion efficiency. This latter problem can be
minimized through experimental development.
There is no fuel penalty associated with evaporative control,
and, in fact, theoretically, there is a slight savings since the fuel
previously lost is available for combustion. Such a benefit, if
attainable, has not been quantified.
A significant reduction in heavy duty evaporative emissions is
expected to be possible with adoption of the current California heavy
duty evaporative standard. The magnitude of such a reduction, 1.3
gms/mile, is small in comparison to the reduction in average HC urban
emissions resulting from the proposed gaseous emission standard (7.9
gms/mile). At an estimated cost of $25 per vehicle, such control would
still be cost effective, but not as cost effective as the control of
gaseous emissions to proposed levels (Ref. Table 15).
The primary reason for the limitation in ability to obtain greater
reductions in evaporative emissions is the lack of a comprehensive test
procedure. The adoption of an enclosure (SHED) procedure is expected
to alleviate this constraint, but requires much development before it
can be applied to heavy duty. An equally important problem is the
method of insuring compliance with evaporative standards because test-
ing requires a total vehicle. EPA currently certifies engines only for
heavy duty and would have to begin dealing with total vehicle manu-
facturers in any compliance program. California has sidestepped this
problem by not requiring a demonstration of compliance. Engineering
judgment is substituted. The inability to insure compliance by certi-
fication testing of all possible vehicle configurations could further
erode the estimates of potential emissions reductions obtainable if
EPA were to merely adopt the California program.
G. Additional Technology Assessment Information
Several months after the technology assessment panel completed
their report, which is summarized in sections A through E, California
held hearings to consider the impact of imposing several alternative
standards more stringent than their current standards of HC +
10 gms/BHP-HR, CO - 30 gms/BHP-HR. Specifically, California
the following options for 1977:
-------
HC HC + NOx NOx _CO (grs/B^-KR)
(1) 5 25
(2) 1.5 7.5 25
(3) 1.5 10.0 25
(4) 1.0 7.5 25
An "either or" standard consisting of options (1) and (4) was sub-
sequently adopted. However, in the course of deliberations, manufac-
turers presented written statements on their ability to comply and the
technology and fuel consumption impacts of option (3) which is within
the range of standards previously considered by the EPA panel (Ref. 13).
The significant findings from these submissions related to the develop-
ment and demonstrated performance of gasoline engines. All manufac-
turers stated that they could meet the levels of option (3) using
current California systems or minor recalibrations of same. The systems
in use are primarily engine modifications (fuel management), AIR, and
some EGR. No changes in fuel consumption from current California levels
were forecast. GM certification data for 1975 show all California
engines currently meet the option (3) levels with slightly improved BSFC
over corresponding 49 state engines certified to higher emission levels.
Very little (one engine family), if any, catalyst usage by gasoline
engine manufacturers was forecast.
Diesel manufacturers could all meet the option (3) levels with
little change from currently certified California configurations.
However, Caterpillar said they could not meet the 1.5 HC level with one
high volume engine family, a direct injection mid-range engine used in
intermediate sized vehicles. Cummins forecast a 5% fuel efficiency im-
provement while other manufacturers cited no change from J75 California
levels.
In summary, the development work forecast by the technology panel
has been continuing such that the breakpoint for non-catalyst techno-
logy capability with no fuel penalty appears to have already moved to
levels of HC = 1.5, CO = 25, HC + NOx = 10 gms/BHP-HR. The use of
"good" technology as demonstrated by GM and Cummins and available to all,
is expected to make_sjaeh_JLeyels achievable in 1979 by all manufacturers
over a full product range even after accounting for the change in HC
measurement procedure.
H. Standards and Recommendations
Based on analysis of data currently available, it appears that
heavy duty engines can meet emission standards more stringent .than
the current Federal requirements. These standards could be applicable
for model year 1979. If not, the lead time necessary to develop and
tool up will require approximately two years from the time a NPRM is
issued.
For HC and CO emissions, the emissions capability of gaso:.i">.o
engines generally is not as good as Diesel engines. Introduction
-------
40
of catalytic control of HC and CO for gasoli-.e engines would brir_r,
their emission level capability close to that of Diesel engines. The
NOx emissions from current Diesel engines, are apprcx-'.nctely IP per-
cent higher than gasoline engines.
Several sets of Heavy Duty emission standards ar«. rossib".'! :'.i
the near term. The range encompassed is as foMows: 1.5 <^ iC J 3.0,
15 <_ CO <_ 30, NOx = 9 gms/BHP-HR. Selecting different standard-, with
in these ranges primarily impacts the technology expectec. to be u::'.." i
which further impacts the complexity, cost and fuel efficiency of the
engines. The standards, their relationship to current standards, and
uncontrolled emissions are shown in Table 12.
-------
41
Table 12
Possible Future H-D Emission Standards
Diesel
HC CO NOx HC+NOx Smoke Smoke Smoke
Uncontrolled
Levels
Current 1974
Standard
% Reduction
from Uncontrolled
1974 Average
Performance
% Reduction
from Uncontrolled
Possible Future
Standard (No
catalyst for
gasoline engine)
% Reduction
from Uncontrolled
% Reduction from
1974 Standard
Possible Future
Standard (No
catalyst for
gasoline engine)
% Reduction
from Uncontrolled
% Reduction from
1974 Standard
Possible Future
Standard (catalyst
on gasoline engine)
% Reduction
from Incontrolled
% Reduction from
1974 Standard
(A)
1.2 6.4 10.5 11.7 27
- 40 16 20
none - none 26%
.9 5 11.2 12 13
25% 21% t-6%] [-3%] 52%
3.0 30 9 - 20
none none 14% - 20%
25% 0%
1.5 25 - 10 20
None none - 15% 20%
38% - 38% 0%
1.5 15 9 - 20
None none 14% - 26%
63% - 0%
(L)
19
15
21%
7
63%
15
21%
0%
15
21%
0%
15
21%
0%
(P)
56
50
11%
22
61%
50
11%
0%
35
38%
30%
35
38%
30%
(gms/BHP-hr)
Gasoline
HC CO NOx HC+NOx
10.2 130 4.9 15.1
40 - 16*
70% - None
3.4* 24 9.9 13*
(53%) 31% [-102%] (3%)
3.0 30 9
71% 77% None
25% -
1.5 25 - 10
85% 81% - 34%
38% - 38%
1.5 15 9
85% 88% None
63%
* NDIR HC
Numbers in ( ) are corrected for instrument difference in sensitivitv between FTD and NDIR.
Numbers in [ 1 are increases in emission rates.
-------
42
No fuel consumption penalty for either set of possible standards
is expected if the manufacturers optimize for both emissions .ir.d fuel
consumption, which is possible using technology wh5.ch can be .ivailaolo
for all engines by 1979. In fact, based on recent light duty vehicle
performance, it is expected that a recovery of any existing fu3l penalty
will be possible if catalyst technology is applied to gasoline T
The first costs associated with the two possible sets of standards
depend on the technology used to meet the standards. Some of the tech-
nical approaches that will be used to meet the standards will involve
costs that are not directly attributable to just the standards. With
fuel consumption a major concern, the engine system choice will require
a more sophisticated system than one that would just meet the emission
standards with no regard for fuel consumption. Therefore, the cost
attributable to just meeting the standards are difficult to quantify.
However, the cost for the entire system, optimized for both fuel eco-
nomy and emissions, can be estimated. These estimates are shown below.
Table 13
Cost Per Engine Over 1974 Base to Meet Possible Emission Standards
Diesel Engine Gasoline Engine
HC/CO/NOx
3/30/9 $120 $ 75
1.5/25/9 $120 $110
1.5/15/9 $120 $165
The standards, which are now stated on a combined basis, can be
expressed separately. However, for reasons discussed in Section III,
a more appropriate method for the interim period is to have a separate
HC standard and a combined HC + NOx standard. The more stringent
individual standards presented in this technology assessment stated
on the combined basis would be as follows:
separate: HC =1.5 gr/BHP-HR HC =1.5
NOx =9 HC + NOx =10
CO =15 CO =15
The fact that combining the HC and NOx is not a simple addition of
the two separate standards is explained by the fact that an individual
standard results in actual performance distributions below the standard
such that, based on past experience, manufacturers will likely have a
sales weighted average HC performance of 1 gm/BHP-HR when certifying
against a 1.5 gm/BHP-HR standard. In addition, there is an inverse
relationship between HC and NOx emissions when using advanced control
systems, such as E6R. Therefore, the probability of having high HC and
NOx emissions simultaneously is very low. Data from 1974 certifica-
tion engines were analyzed to demonstrate this phenomenon. Figure 5
illustrates the standards for HC and NOx which would be appropriate
to the existing 15 gm/BHP-HR HC + NOx standard.
-------
X - 3.4
HC NOx HC+NOx (gr/BHP-FR)
(a) 95% of engines certified below these levels.
Combination of HC and NOx Performance
To A Combined Standards Level
Thus, in terms of current gasoline performance, HC levels of 5 and
NOx levels of 12 correspond with a combined level of 15, 2 grams lower
than a simple addition of the two performance levels. Standards of ap-
proximately HC = 6 and NOx = 13 would be appropriate if a 16 gram
standard were stated separately.
Although a reduction in smoke levels from current performance was
not considered in the technology assessment and all manufacturers
indicated their development work on gaseous emissions was based on no
further reductions in smoke levels, there is a need to reexamine the
smoke standards. This is true because current performance is well below
the standards for peak smoke and it would be counter productive to allow
manufacturers to degrade smoke performance in achieving reduced gaseous
emission levels.
-.
The 1974 certification peak smoke levels were analyzed and are pre-
sented in Figure 6. These data show that 99% of all Diesel engines are
below 35% peak smoke opacity:;- Furthermore, a more recent examination
of 1975 Federal and California engine certification data indicated that
the ability to meet a 35% peak smoke level has been demonstrated in at
least one test engine for every Diesel engine family. All Diesel engines
certified in California to gaseous standards similar to those under con-
sideration here currently meet a 35% peak value. Therefore, a change in
the peak smoke standard from 50% opacity to 35% opacity should, be made as
protection against future degradation.
Exhaust gaseous emission standards of HC = 1.5, CO = 25, HC + NOx =
10 gm/BHP-HR are recommended for the following reasons: 1) Non-catalyst
technology exists to meet these standards without a fuel penalty; 2) The
intermediate CO level of 25 will allow all manufacturers to meet the
standards with little or no catalyst usage. Gasoline engine first cost
increase is, therefore, minimized. For Diesel engines, the total cost
represents less than 0.1 cent per operating mile; 3) The lower standards
represent approximately the same relative stringency as the interim LDV
emission standards (80% reduction from uncontrolled), and 4) The degree
of GO control lost (25 versus 15 gms/BHP-HR) is not as great as the
numbers indicate because the 9 mode test over estimates urban emission
reductions. Diesel engines already meet the 15 level.
-------
Figure 6
3
1974 CERTIFICRTION
SRLES*flNO DIESEL SMOKE EMISSIONS - PERK
o<
0
"« ««
11.77%
0.55% 0.42Z
31"35 36-40 41-45
o.oo/;
"Ye-S'b
PREPARED BY: EPR, MS.RPC.DPM, DB 07~,'>P-7U
' Projected family sale- arc equally split for each certification test.
o
51
-------
v- Emission Control Cost EffectivenesF
The cost effectiveness of an emission control option depecds on
several factors whose combined costs, coupled with an erirVrjate of
emission reductions from some baseline level, yielc a staristic (in
dollars per ton of pollutant or equivalent ;nit?y which cen be cc?1-
pared to other control options. For tho purpose of this analysi',
the baseline levels of emissions are those which existec. immediately
prior to implementation of the control option of interest. Ths costs
to control from these levels to the levels u'der consideration include
development costs, manufacturing costs, operating costs, and r^ai-p-
tenance costs. Manufacturing costs have been estimated from manu-
facturer supplied data and technology assessment. Operating costr
amount to the fuel penalty associated with each control option.
Maintenance costs are those associated with the repair and re-
placement of components which would not have been present in pre-control
option vehicles or were adversely affected by the operation of the
given emission control option.
Table 14 presents background information necessary to calculate
cost effectiveness for the previously discussed options. The cost ef-
fectiveness of implementing LDV interim standards is included for com-
parative purposes. No attempt has been made to determine the cost ef-
fectiveness of a VMT reduction option. Such an option results in large
fuel consumption decreases and, from that standpoint, is attra-:-ive.
However, implementation of such an option involves determining costs
for the development and operation of effective mass transportatior
systems along with public inconvenience. These costs are extremely
difficult to assess.
Cost effectiveness is calculated using the following equation:
Control System Cost Over Useful Life
Cost Effectiveness ($/ton) = Emissions Reduction (tons/mile) x
Total Lifetime Miles
where
Control System Cost Over Useful Life = Development Cost +
Manufacturing Cost + Maintenance Cost + Operating Cost
Total lifetime miles have been calculated from References 14 and 15
by computing scrappage rates and average annual miles as a function of
vehicle age. The lifetime miles used in the cost effectiveness calcul-
ations are:
LDVs 100,000 miles
LDTs 100,000 miles
HDVs-gas 160,000 miles
HDVs-Diesel 436,000 miles
-------
Using tat data presented r.r. Table 14 as .-Inputs to the cost
effectiveness equation, Table ..' vzs orcparcd showing cos; effective-
ness in S/ton for each control option.
An analysis of Table 15 indicates that the ir.itiil i^TJ
of catalyst control options on a giv-n mobile source i? ">:<':r>"3<-ly c;o3.
effective since such an option does not result in fuel ccnsui^tior.
penalties from uncontrolled levels. Thus, control o- LDVc, I/JT', nrd
HDVs to interim levels which require the application of catal>s':s
actually results in a cost davings, on an individual vehicle har.is,
over existing control options for these categories. In contrast, control
from one catalyst option to another does not result in any cost savings.
Considering just a cost effectiveness argument, LDT and HDV interim
control is more cost effective than LDV control in excess of the
interim levels.
Given that additional air quality reductions are needed, as is the
case in many AQCRs, additional controls on HDVs and LDTs are more ef-
fective than transportation control plans for LDVs and LDTs in reducing
the mobile source emission contribution, and technologically more
feasible than reducing LDV standards below the statutory levels. In
fact, additional HDV control is the most cost effective mobile source
control option for reducing hydrocarbon emissions over current levels
and is more cost effective than going from LDV interim to LDV statutory
standards. Although the proposed LDT and HDV strategies will result
in additional NOx and CO reduction, these reductions, based on a
national vehicle mix, are of a lesser magnitude than those which are
obtained by going from interim to statutory control levels for LDVs.
However, implementation of LDT standards and HDV standards is more
cost effective than going from LDV interim to statutory standards.
Inspection/maintenance for LDVs and LDTs, while providing additional
HC and CO control, is not as cost effective as stricter standards for
LDTs and HDVs.
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Table 14
Background Information on Cost Effectiveness for Various Control Options
Operating Cost-
Baseline Emission Levels Proposed Emission Levels Fuel
Base (Expressed in Urban Equivalent Values) Consumption
Development a/
+ Manufacturing
+ Maintenance
Option
LDV/N -*-LDV/l
LDV/I-w-LDV/S
(HC, CO)
LDT/N-»-LDT/I
HDV/N-^HDV/I
gas
Diesel
HDV/N-*-HDV/I
gas
Diesel
HDV /N -»- HDV /I
gas
Diesel
LDV, LDT/IM
LDV, LOT EVAP
(6gms/test)
Year
1974
1976
1975
1974
1974
1974
1974
1974
1974
1978
HC
3.
1.
3.
11.
3.
11.
3.
11.
3.
15%
1.
4
5
2
1
8
1
8
1
8
7
CO
grams/mile
39.0
grams/mile
15.0
grams/mile
33
grams/mile
139
25.3
grams/mile
139
25.3
grams/mile
139
25.3
reduction from
HC and
~
Nox HC
3.
2.
4.
14.
22.
14.
22.
14.
22.
1
2
4
0
4
0
4
0
baseline
CO
~
1.
1.
3.
3.
6.
3.
3.
3.
5
41
7
2
8
9
8
2
8
CO
grams/mile
15.0
grams/mile
3.4
grams/mile
18
grams/mile
140
25.3
grams /mile
146
25.3
grams/mile
127
25.3
Nox Change c/
2. -13.8%
2. 0%
2.3 0%
13.3 0%
19.9 0%
13.3 0%
19.9 0%
13.3 0% b/
19.9 0%
Cost
S230
$125
$ 66
$110
$120
$ 75
$120
$165
$120
levels of -8%
6
~
0%
S 7.30
a/ Control system costs over the useful life for each option are split among all pollutants for LDV,
LOT, and HDV gas options, assigning cost to the pollutant each component is to control. For the
HDV Diesel options, all costs are associated with NOx control since no additional HC or CO control
is obtained.
b_/ Fuel change information is based on General Motors estimates. These estimates, along with ECTD
cost estimates, compiled from discussion with the HDV manufacturers.
c/ A negative change implies a decrease in fuel consumed.
I - Interim Strategy
IM - Inspection Maintenance
N - No Further Control
S - Statutory Requirement
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Table 15
Cost Effectiveness of Proposed Federal Emissions Control Programs
Control Program
LDT Interim
Standard
Baseline Emissions
Program Emissions Level I/
1974 LDT
Standard
HDV
Current
Control
EPA Administrators 1975 Fed.
Proposed 1980-81 LDV
Fed.Standards 2J Standards
LDV Fed.
Statutory Stds.
HDV Fed.
Interim
Standard
LDV/LDT TH 4_/
LDV/LDT iiVAP
1975 Fed.
LDV
Standards
2.0/20/3.1
5.5/58/6.3
1.5/15/3.1
1.5/15/3.1
3/
1.7
Emissions After Control
Program Initiated
1.7/18/2.3
.9/9.0/2.0
.41/3.4/2.0
3/
.6
I/
All emissions factors in grams per mile HC/CO/NOx, except for HDV.
Cost of Control ($/ton)
HC
202
303
437
Gas 20-23
Diesel
61-414
50
CO
14
30
41
0-3
4-29
NOx
53
165
165
136-M7
4f; 119
00
Decision of the AdminiRtrafor, Application for Suspension of 1977 Motor Vehicle Exhaust Emission Stam.jrd,
Msif.:li 1975.
21
J/ H«*a«y fluty Vehicle (HDV) emissions levels based on 1974 vs. proposed 1979 HDV emissions stan'ardc.
Stindards: 16 grams/bhp-hr (HC + NOx), 40 grams /bhp-hr .(CO).
7" i'rouosed Standards: 1.5 grams/bhp-hr (HC), 25.0 grams/bhp-hr CO, 10.0 grams/bhp-hr (NOx).
'M ('iKt Effectiveness calculations assume a 30% failure rate.
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49
References
1. NOx Analysis Report, Vol. I, Office of Air Quality ?..anning .d
Standards EPA, September 21, 1973.
2. Position Paper on A Revised Light Duty Truck ... ~t by ECTJ,
EPA, September 18, 1974.
3. "1973 Motor Truck Facts", Motor Vehicle Manufacturers Asscciation
Publication.
4. Highway Statistics/1972, U.S. Department of Transportation,
Federal Highway Administration.
5. "Mass Emissions from Diesel Trucks Operated Over a Road Course",
EPA Report. No. 460/3-74-017, August 1974.
6. "In-Use Heavy Duty Gasoline Truck Emissions: Part I, Mass
Emissions from Trucks Operated Over a Road Course", EPA Report
* No. 460/3-73-002-a, February 1973.
7. Vehicle Operations Survey Prepared for Coordinating Research
Council and EPA by Scott Research Laboratories, Inc., December 17,
1971.
8. "Emissions Control Technology Assessment of Heavy Duty Vehicle
Engines", EPA Report No. 460/3-74-007, December 1973.
9. Substitution of Percent Load for Manifold Vacuum in the Heavy
Duty Gasoline Test Procedure, C. J. France, September 30, 1974.
10. Proposed Interim' Regulation Instrument Changes for Heavy Duty
Vehicle Gaseous Emissions Measurement, W. B. Clemmsns,
October 24, 1974.
11. Impact on Existing Standards Due to Proposed Instrumentation
Changes in the Heavy Duty FTP, W. B. Clemmens, September 18, 1974.
\
12. Letter from Robert E. Neligan to John P. DeKany, July 26, lilt-.
Subject: Heavy Duty Vehicle Emission Control Strategies.
.*
13. "An Assessment of the Current State of the Art and Future
Possibilities for Emission Control for Heavy Duty Engines",
prepared by ECTD,-. November 18, 1974.
14. "Truck Inventory and Use Survey", 1972 Census of Transportation,
U.S. Department of Commerce, October 1973.
15. "Automobile Exhaust Emission Surveillance - Analysis of the
FY 72 Emission Factor Program", EPA Report No. 460/74-001.
February 1974.
16. Environmental and Inflationary Impact Statemert, Jnt'srin H2avy
Duty Engine Regulations for 1979 and Later Model Years, 19"">.
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