State and Federal Standards for Mobile-Source Emissions (2006) / Chapter Skim
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4 Co-evolution of Technology and Emissions Standards
4 Co-evolution of Technology and Emissions Standards
Pages 114-135
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From page 114... ...
The efforts of motor vehicle manufacturers, the manufacturers of emissions controls and other equipment, the California Air Resources Board (CARB)
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From page 115... ...
. Lack of progress on air pollution control in California and elsewhere in the United States prompted Congress in the 1970 CAA amendments to feature ambient air quality standards with deadlines for their attainment and a technology-forcing program to reduce emissions from vehicles (Muskie 1990)
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From page 116... ...
Section 202(k) requires EPA to develop standards for evaporative emissions control that "shall take effect as expeditiously as possible and shall require the greatest degree of emission reduction achievable by means reasonably expected to be available for production during any model year to which the regulations apply, giving appropriate consideration to fuel volatility, and to cost, energy, and safety factors." Section 213 of the 1990 CAA amendments requires that nonroad emissions standards, which at that time were uncontrolled, "achieve the great
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From page 117... ...
Engine and Exhaust Controls Table 3-3 in Chapter 3 displays a chronology of federal and California exhaust emissions standards for new passenger vehicles. Allowable emissions for light-duty trucks have been reduced at a similar pace, although emissions standards for these vehicles were not as low as those for passenger vehicles until recently.
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From page 118... ...
. Pre production testing must demonstrate that vehicles will comply with emissions standards at the end of their useful life, which is 120,000 mi for present-day light-duty vehicles.
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From page 119... ...
Bench-aging of cata lysts is one method for testing durability of emissions-control sys tems, as opposed to accumulating full useful-life mileage on an ac tual vehicle. Once the useful-life emissions of an emissions control system/configuration have been determined, it must be shown to re sult in emissions below the certification levels on production vehicles.
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From page 120... ...
-- Material in the detail seals on the carburetor is claimed for reduced permeation and increased purge. · Enhanced evaporative emissions controls (1996 to present)
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From page 121... ...
EGR is also used to reduce NOx emissions from diesel engines. Exhaust emissions-control devices consist of catalytic converters and air injection systems.
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From page 122... ...
Source: MECA 2003. Reprinted with permission; copyright 2004, Manufacturers of Emissions Control Equipment.
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From page 123... ...
The scope of improvement has allowed the three-way system to achieve the progressively stricter California and federal standards. Electronic Controls and Onboard Diagnostics Electronic controls on light-duty vehicles involve the use of onboard computers, sometimes known as engine-control units, and oxygen sensors and enable the adoption of closed-loop fuel control.
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From page 124... ...
Onboard diagnostic (OBD) systems are incorporated into the computers of vehicles to monitor the performance of the emissions controls.
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From page 125... ...
have been required since 1994 to meet a CO limit of 10 g/mi on certification tests conducted at 20°F. To meet stricter emissions standards, including the cold-start CO standards and federal Tier 2 and California LEV II standards, vehicle
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From page 126... ...
126 State and Federal Standards for Mobile-Source Emissions FIGURE 4-5 Average CO emissions for a 111-vehicle test sample taken in Fairbanks and Anchorage, Alaska, under temperatures ranging from -34° F to 14° F ("94 & Newer" applies to model years 1994-1998)
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From page 127... ...
Evaporative Emissions Control Evaporative emissions are the HCs that escape from the vehicle that do not come from the tailpipe. Originally, losses due to the evaporation of residual fuel in the fuel metering system and diurnal fuel tank losses were of concern.
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From page 128... ...
Among this project's conclusions was that reducing sulfur concentrations from 450 to 50 ppm would result in over a 10% decrease in CO and HC exhaust emissions in 1990 model year vehicles. Although the impacts of sulfur are not as severe as the impacts of lead in gasoline, sulfur in fuel is converted during combustion to various sulfur-containing compounds that react with the catalyst surface and in
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From page 129... ...
. It was not until the 1977 CAA amendments that technology-forcing requirements for diesel particulates and NOx were adopted, calling for heavy-duty diesel engines to achieve the greatest emissions reduction achievable consistent with consideration of costs, technology feasibility, and other factors.
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From page 130... ...
, exhaust gas recirculation (EGR) , and oxidation catalyst technologies.
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From page 131... ...
, snowmobiles, motorcycles) The 1990 CAA amendments directed EPA to prepare a study of the scope and sources of nonroad emissions and to regulate them if they were found to make a substantial contribution to nonattainment of ozone or CO ambient air quality standards.
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From page 132... ...
Nowhere is the coop TABLE 4-3 Possible Emissions-Control Technologies for Nonroad Mobile Sources · Spark-Ignition Engines Fuel injection and feedback control systems Exhaust gas recirculation systems Three-way catalysts and advanced catalyst systems High-energy ignition Hybrid electric systems Advanced combustion system design and control · Compression-Ignition Engines Turbocharging Intercooling Cooled exhaust gas recirculation systems Oxidation catalysts Selective catalyst reduction system Lean NOx catalysts NOx storage catalysts Catalyzed particulate filters Hybrid electric systems
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From page 133... ...
Nearly all large farm and construction equipment is diesel powered and can share control technology with heavy-duty trucks. Spark-ignition engines in farm and construction applications may use versions of gasoline heavy-duty-truck emissions controls.
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From page 134... ...
CONCLUSIONS The basic elements of mobile-source emissions control result from the co-evolution of emissions-control research and the promulgation of vehicle and engine emissions standards. A central concept of the standards-setting process for mobile-source emissions is technology forcing.
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From page 135... ...
· Over the almost 50 years of mobile-source emissions regulations, controls have evolved from the use of simple technologies to control light-duty vehicles to today's sophisticated integration of engine, fuels, and emissions-control technologies to control emissions from an array of mobile sources. Compared with emissions rates of 1967 modelyear light-duty vehicles, the rates of new, properly operating vehicles decreased by 95-99%.
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