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7. DISCUSSION
Introduction
As a result of the Clean Air Amendments of 1970, automotive
and related manufacturers - both within and outside the United States
have embarked upon research, development, and manufacturing programs
designed to meet the newly established emission standards for light-
duty motor vehicles. As observed in the January 1972 report of this
Committee, it is unfortunate that the automobile industry did not seri-
ously undertake such a program on its own volition until it was sub-
jected to governmental pressure. A relatively modest investment, over
the past decade, in developmental programs related to emission control
could have precluded the crisis that now prevails in the industry and
the nation. The current crash programs of the major manufacturers have
turned out to be expensive and, in retrospect, not well planned.
Nevertheless, the almost world-wide effort to achieve the fed-
eral emission standards set for the light-duty motor vehicles in the
United States has produced a significant rate of progress toward meet-
ing the requirements of the Clean Air Amendments of 1970. It is the
very pace of that progress that complicates judgment today concerning
the most appropriate course of action with respect to attainment of
the standards required by that law.
As discussed in earlier parts of this report, several systems
have been shown capable of attaining emission certification in 1975
model year cars. Among these are the diesel (discussed in Section 6.1)
and the three systems discussed in Section 3.2 (the conventional engine
with modification and oxidation catalyst, the Wankel with a thermal
reactor, and the carbureted three-valve stratified-charge engine). While
continued progress can be expected in development of all these systems,
they do not possess equally desirable characteristics.
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Several control systems in early states of development have
met the 1976 standards at low mileage. Some of these represent fur-
ther development of systems designed for certification and manufacture
in model year 1975. Others are relatively new and their ultimate manu-
facture will require energetic commitment by the industry to further
develop approaches that have been pursued only in smaller companies
and at relatively low levels of effort. One system promises to be ac-
ceptable in use for the full 50,000 miles. Durability and other per-
formance data are already available for that system. The future per-
formance and acceptability of other systems - especially those currently
being developed by the principal manufacturers - remain in doubt. In
the following discussion, we shall briefly compare those systems that
warrant consideration for certification and production in model year
1976.
7.2 Dual-Catalyst System
To date, the belated research and development programs of the
major automobile manufacturers have been devoted almost entirely to
the development and incorporation of such minimal modifications to the
basic spark-ignition, internal-combustion engine as may be required to
achieve certification in 1975 and 1976. This situation is a result of
the short time between passage of the Act and the scheduled date of its
enforcement, and the desire of the manufacturers both to protect their
investments in the internal-combustion engine and to utilize their vast
experience with this engine. The modifications made to achieve ~mis-
sion levels required by the 1973 federal standards represent just such
continued development of the conventional engines of previous years.
To achieve the further reductions called for by the 1975 and
1976 standards, most major manufacturers currently plan to use cata-
lysts in the exhaust stream to promote both oxidation of carbon monox-
ide and hydrocarbons and chemical reduction of NOx. The CMVE believes
that engines equipped with oxidation catalysts will be able to meet
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the certification requirements for model year 1975. At this time, no
experimental engine modified to include the dual-catalyst systems has
exhibited the durability required to achieve compliance with the 1976
standards. Nevertheless, assuming a continuation of the intensity of
the current effort, extrapolation of the rate of recent progress sug-
gests that catalysts with the durability required by the 1976 standards
will be developed. But it cannot be stated with certainty that such
developments will occur in time for 1976 production of automobiles.
Although American manufacturers and others evidently will be
able to produce catalyst-equipped vehicles capable of certification
for the 1975 model year, and even possibly capable of 1976 certif~ca-
tion, compliance with the certification procedure, of itself, may not
constitute indication of satisfactory performance of catalyst-equipped
vehicles in actual customer use. As discussed in Section 4.2, the
diverse conditions to be undergone by the engine and control systems
during 50,000 miles of customer use are far more strenuous than those
undergone during certification. These more strenuous conditions may
result in significant damage to a catalyst. In view of the performance
history of catalytic systems observed to date on experimental vehicles,
under laboratory conditions, there is concern that there may be frequent
catalyst failure under conditions of actual use well before a scheduled
25,000-mile replacement.
Admittedly, there has not been actual customer-like experience
with catalytic systems that have met the 1975 or 1976 certification
requirements, and these concerns may be overdrawn. Furthermore, £ail-
ure in service of cars properly maintained and used will call into
operation Section 207(c) of the Act, by which the manufacturer can be
forced by EPA to remedy the deficiency at his own expense. Obviously,
this concern would be relieved by either the expected early develop-
ment of catalysts demonstrably more rugged and durable than those tested
to date, or by demonstrated satisfactory performance, in conditions
similar to customer use, of those catalysts now under investigation.
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Only one manufacturer has commenced such tests with a few cars equipped
with a single-catalyst system that have met the 1975 standards. Final
judgment of the actual performance of such systems must await experi-
ence .
7.3 Alternatives to the Dual-Catalyst Approach
In view of the fact that the dual-catalyst approach to a non-
polluting automobile power plant may not lead to a truly satisfactory
long-term solution to the environmental problem, it is encouraging to
note that promising alternative systems are under intensive investiga-
tion. Although some are only in the earls est stages of development,
others are more advanced and promise to achieve 1975 emissions certi-
fication when utilized on smaller engines. These include the carbu-
reted three-valve stratified-charge engine, the modified diesel, and
the Wankel with Heal reactor. Each of these alternative systems is
described below.
7.3.1
Carbureted Three-Valve Stratified-Charge Engine
Prototype compact cars equipped with the carbureted three-
valve stratified-charge engine have met the 1975 standards for 50,000
miles. Three tests on vehicles equipped with an advanced version of
this system show average low-mileage emissions of 0.25 grams per mile
HC, 2.50 grams per mile CO, and 0.43 grams per mile NO (see Table 3-11~.
This system should be capable of certification on small cars in time
for model year 1976 production, and with an adequate margin of safety
for each of the three contaminants. This approach should also be ap-
plicable to larger engines, but sufficient experience is not yet avail-
able for evaluation.
A substantial degree of confidence can be placed in the esti-
mation that the emissions performance of this engine in use will be
quite close to its performance during certification. The maintenance
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required on the carbureted stratified-charge engine should be no
greater than that required on a conventional 1973 engine. In fuel econ-
omy, this engine is comparable with a 1972 engine and much superior to
a dual-catalyst-equipped 1976 engine.
7.3.2 Diesel Engines
Emissions achieved by a current diesel-powered vehicle are 0.15,
2.5, and 1.65 g/mile for HE, CO, and NOx, respectively, and this engine
is certifiable for 1975 production. Further improvements are possible,
but much innovative engineering work must still be done before the diesel
can meet the 1976 standards. Limited production of adequately improved
vehicles might be possible by 1980. Since the diesel would provide a
significant fuel economy, even compared with 1972 engines, further
development of the diesel warrants encouragement.
7.3.3 Wankel Engines
As shown in Table 3-7, the Wankel engine with thermal reactor
on a compact car has met the 1975 standards with NOx levels of about
1 g/mile for 50,000 miles, but with a fuel penalty of about 30 percent
compared with a 1973 equivalent piston engine. The use of EAR and
richer carburetion can probably further reduce NOx levels, but at the
cost of even greater fuel consumption, and even so it is not yet cer-
tain that the 1976 standard for NO can be achieved.
x
Durability performance of the Wankel engine with thermal re-
actor on a compact car has been shown to be superior to that of the
dual-catalyst system. However, temperatures experienced by the reac-
tor during operation in the hands of the public should be somewhat
higher during certain driving modes, and durability under such condi-
tions has not been established.
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7 .3 .4 Catalytic Systems with Feedback Control
A system with three-way catalyst and feedback control (see
Section 3 . 6) promises improvement over the dual-catalyst system. How-
ever, adequate durability data with respect to both the catalyst and
the oxygen sensor are not available to make meaningful estimates of
the performance of such systems either during certification or in use.
Feedback control of a dual-catalyst system would be expected
to increase the life of the catalyst, reduce emissions, and signifi-
cantly improve fuel economy. At this writing, such a system is not
available but may be capable of development, though perhaps not in
time for production in quantity in 1976.
7 .4 Interim S tandard s
According to the work statement agreed to by the EPA and the
National Academy of Sciences, "Should the Contractor conclude that the
attainment of emission standards on the schedule provided by Section
202 (ball) of the Clean Air Act is not technologically feasible, the
Contractor shall specifically determine technologically feasible
interim emission levels to assist the Administrator in exercising his
responsibilities under Section 202(b)~5) of the Act." However, the
considerate ons that must enter into the determination of optimal tech-
nologically feasible interim standards are so complex and carry so
many implications that, as explained below, it is inadvisable and in-
appropriate for this Committee to recommend a specific set of interim
levels at this time.
It is not yet possible to make a definitive prediction with
respect to which engine systems will achieve certification for 1976.
The most likely candidate is the carbureted stratified-charge system
on smaller engines ~ It is probable that others, particularly the dual-
catalyst system, will also qualify at that time. It is conceivable
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that the projected automobile production for 1976 can be achieved only
by a mix of engines, some certifiable and some (probably larger engines)
not quite certifiable. However, while it is premature to judge the
issue at this time, a rationale may later be required for upward ad-
justment of one or more of the standards to permit production of a suf-
ficient number of vehicles of various sizes in 1976.
Examination of possible interim standards for the three pollu-
tants is complicated by the fact that the technologically feasible
levels of the three pollutants are interdependent. For several of the
systems discussed, further decreases in NO can be achieved, for exam-
ple by greater reliance upon EGR, but only by accepting higher levels
of CO and HC. Thus, before selection of a particular set of interim
levels as achievable, answers will be required to such questions as:
Is it more important to reduce NOX emissions than CO or HC? Or vice
versa? Further, compact cars are capable of lower emissions than are
standard or large cars with similar control systems, while consuming
less fuel. What emphasis should be placed on significantly different
levels of fuel consumption that are associated with the various control
systems and vehicle sizes and the substantial possible impact on total
petroleum requirements?
The Committee made no attempt to resolve these and related
questions, as judgments regarding these matters were deemed to be be-
yond the scope of the study commissioned to the Academy and delineated
by the EPA-Academy contract. Thus, at this time, the Committee finds
it inadvisable to recommend a specific set of interim standards.
7.5
Effects of a Delay in Enforcement on Total Automobile Emissions
To illustrate the ef fects of various delays in implementing the
emissions standards, should this be found necessary, a computer model
was used to calculate total automotive emissions in a typical metro-
politan area for the years from 1960 to 2000. This model accounted
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for factors such as vehicle age distribution among all automobiles,
the decrease in vehicle miles driven per year per car as vehicle age
increases, the predicted nationwide growth in vehicle population each
year, the emission reduction achieved through crankcase blowby and
evaporative-loss control, the effect of federal exhaust-emission stan-
dards, and deterioration of emission controls with mileage. Vehicle
age distribution was taken from a national average automobile popula-
tion, which is a reasonable distribution for many large urban areas.
Urban driving was assumed in the model, and average emissions for urban
driving were used. These emissions values were obtained from records
for 1972 and older model-year cars. For cars built or to be built after
the 1972 model year, the emissions values were based on various ~mple-
mentation plans.
Figures 7.1, 7.2, and 7.3 show the variations in emissions of
HO, CO, and NOx, respectively; these curves are normalized against the
maximum for each contaminant. Four cases are represented in each set
of curves:
1. Standards maintained at the 1973 levels indefinitely.
r
2. 1975 and 1976 standards implemented and met on
schedule.
3. 1975 and 1976 standards each delayed one year --
the maximum allowable under the law.
4. 1973 standards maintained through 1976 model year
and 1976 standards implemented in 1977 model year.
The Implementation of emissions controls since 1968 has already
caused an appreciable reduction in annual emissions of HO and CO, but
little reduction in NO . Federal standards for model year 1973 cars
call for decreases of approximately 80 percent for hydrocarbons,
- 120 -
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70 percent for carbon monoxide, arid 50 percent for oxides of nitrogen,
all measured in relation to the uncontrolled emissions of pre-1968
vehicles. As seen in the curves, were 1973 standards to remain in force,
total emissions of hydrocarbons and carbon monoxide would continue to
decline for some years, as would that of NO . Preponderantly, these
ef fects ref lect the removal from service of older, uncontrolled, or
less-well-controlled automobiles.
7.6
Implementation of 1975 and 1976 Standards and Related Matters
Of two promising candidates for certification and production in
1975 and 1976 - the dual-catalyst system and the carbureted stratified-
charge engine - only the forager is planned for manufacture on a scale
commensurate with expected requirements in those years. Even if durable
catalysts became available, the dual-catalyst system would still have
several undesirable characteristics, the more important of which are
listed below.
1. The dual-catalyst system is expected to have poor
fuel economy. Improvements in fuel economy could
be obtained by the use of proper feedback control
mechanisms, but these are unlikely to become avail-
able for production in 1975 or even 1976.
2. Dual-catalyst systems will have a higher initial
cost, be more difficult to maintain, and be less
durable.
3. Manufacture of vehicles equipped with single- or
dual-catalyst systems in large numbers before
sufficient experience with these devices under
actual diverse consigner use is precarious.
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Independent of whether each car must periodically
pass inspection or whether the manufacturer is
repeatedly compelled to exercise the recall pro-
visions of the Act; if a large fraction of all
cars markedly exceeds the emissions standards,
the entire rationale of this procedure becomes
suspect.
4. The 1973 class vehicles when converted to 1975-76
systems can be expected to be more difficult to
start, thus wasting some fuel and increasing emis-
sion of pollutants (although it should be possible
to mitigate this situation by future technical
improvements).
The circumstances recounted above - the probable certifi-
ability of the carbureted stratified-charge engine under both 1975
and 1976 standards but its relatively limited planned production,
particularly in 1975, and the considerable promise of other, as yet
incompletely developed systems - make judgment concerning an optimal
national approach to decision concerning the scheduled implementation
of the 1975/1976 standards extraordinarily complex - precisely because
the entire research and development aspect of this situation is very
much in flux and changing rapidly.
Some members of CMVE are concerned that strict enforcement of
the provisions of the Act might, by forcing adoption of the control
system first to be developed and certified, defeat the goal of the
earliest possible atta~.~nt of compliance by the most generally
desirable means. These members of CMVE believe that, once having
embarked upon large-scale production of the catalyst-dependent control
systems, several years would elapse before major manufacturers would
alter course in favor of producing more generally satisfactory vehicles.
This would happen, it is thought, because it would be consistent with
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the tradition of the industry of slowly improving technology already
in use rather than switch to a significantly new and different tech-
nology not yet tried on a mass scale. Further, there is concern that
existing market mechanisms would not suffice to accelerate conversion
to a substantially different technology at a pace cons stent with the
overall national interes t .
A minority view within the COVE states that: (a) only rigor-
ous enforcement of the Act will assure the pace of continued progress
toward the goals of the Act; (b) by the time 1975 cars are placed in
product) on, the catalysts used ~ n catalyst-dependent systems may prove
decidedly more reliable than are those now available; (c) there is no
assurance that the additional development time would not simply be
employed by the major manufacturers for further development of the
present systems; and (d) the presence on the market of even a small
number of alternative control systems that are more reliable, cheaper,
and accompanied by a lesser fuel penalty, if any, would constitute an
effective market device, which, without other intervention, would as-
sure changeover by the major manufacturers at an acceptable pace, par-
ticularly if the recall provisions of the Act are enforced as warranted.
The majority view of CtIVE suggests that, on balance, it may be
prudent for EPA to consider a delay in the imposition of 1975 and 1976
standards, lout no longer than that provided for in the Act. It is
thought that this would provide the manufacturers an opportunity to
consider and implement alternative and, quite possibly, more generally
satisfactory technologies with which to attain the goals of the Act.
In this view, as shown in Section 7.5, such an action would not result
in an unacceptable deceleration in reduction of automotive emissions.
In its work' CMVE became aware of a continuing controversy
concerning the stringency of existing emission standards. Strongly
held differences of interests and views surround all the major factors
that affect the selects on of automat ve emission standards: the
- 126 -
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health effects of individual pollutants, their relation to ambient
concentrations, the relationship of total emissions to primary and
secondary ambient pollutant levels, the contribution of automobile
usage to total emissions, and the possible relative reductions in
remissions from stationary and mobile sources. Some of the issues
posed by these considerations are resolvable only by further scienti-
fic research; all will require the attention of officials concerned
with pollution control.
These matters are so complex and important that the Committee
strongly urges an early and thorough reexamination by Congress, EPA,
and the Academy of all aspects of motor vehicle pollution standards
established in the Clean Air Amendments of 1970 -- their premises,
underlying assumptions, the goals that were set, and the interplay
among the three pollutants dealt with specifically in the Act. In the
light of the material developed in its study, CMVE believes that such
a reexamination would be extremely valuable in relating motor vehicle
emission control to the many issues relevant to a sound national
environmental policy.
- 127
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Representative terms from entire chapter:
fuel economy
