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In response to a growing need for a practical and technically valid method for measuring exhaust sound pressure levels (SPL) of on-highway motorcycles, the SAE Motorcycle Technical Steering Committee has developed Surface Vehicle Recommended Practice J28251, “Measurement of Exhaust Sound Pressure Levels of Stationary On-Highway Motorcycles,” which includes a new stationary sound test procedure and recommendations for limit values. Key goals of the development process included: minimal equipment requirements, ease of implementation by non-technical personnel, and consistency with the federal EPA requirements; in particular, vehicles compliant with the EPA requirements should not fail when assessed using J2825. Development of the recommended practice involved a comprehensive field study of 25 motorcycles and 76 different exhaust systems, ranging from relatively quiet OEM systems to unbaffled, aftermarket exhaust systems.

Carbon dioxide (CO2) is the primary greenhouse gas emitted by gasoline-powered motor vehicles, and the amount of CO2 emitted depends directly on the amount of gasoline burned by the vehicle. Any reduction in vehicle fuel consumption will also reduce CO2 emissions, and any reduction in CO2 emissions requires a reduction in fuel consumption. In 2004, pursuant to Assembly Bill (AB) 1493, the California Air Resources Board (CARB) adopted greenhouse gas emission standards for new vehicles that would require substantial reductions in CO2 emissions and fuel consumption from light-duty motor vehicles. In December 2007, Congress made significant amendments to the Corporate Average Fuel Economy (CAFE) program with the passage of the Energy Independence and Security Act of 2007 (EISA2007). After the President signed EISA2007 into law, U.S.

Concerns regarding U.S. dependence on crude oil from politically unstable regions and the impact of fuel combustion on climate change have led to new state regulations and proposed additional federal regulations requiring reductions in fossil fuel use by passenger cars and light-duty trucks. Significant reductions in fuel consumption can be achieved while maintaining the performance and size of current production vehicles; however, it does not appear that the benefits will be commensurate with the costs. Based on the same model employed by the United Nations Intergovernmental Panel on Climate Change, nationwide reductions in light-duty motor vehicle greenhouse gas emissions of 30% will have no measurable effect on ambient temperature. This calls into question the assumption that the cost of reducing greenhouse gas emissions has corresponding economic benefits related to the moderation of climate change.

The constant volume sampling (CVS) technique, which has been part of the Federal Test Procedure (FTP) for the exhaust emissions testing of light-duty vehicles since the 1972 model year, involves the collection of a sample of exhaust gas after it has been diluted to a constant volume. The FTP specifies a formula for calculating a dilution factor (DF) that is used to correct the emission measurement for the pollutant concentration in the dilution air. Once the DF has been determined, emission measurements made using the CVS technique can be converted to a “raw,” undiluted concentration. This enables a single sampling system to be used to determine either mass emissions or tailpipe concentrations, both of which are required in certain vehicle inspection and maintenance (I/M) programs. Review of the DF calculation procedure specified in the FTP indicates that it is a simplification of a more rigorous calculation needed to most accurately determine the true DF.

Comparison of before-repair and after-repair test results for approximately 800 1981 and later model cars and light trucks recruited from customer service shows that the primary cause of excessive emissions depends on fuel metering technology (i.e., carburetor versus fuel-injection). With carbureted vehicles, mechanical component failure is the largest contributor to excessive emissions. Specifically, the need for adjustment or other repair of the carburetor is the single greatest cause of excessive emissions for carburetor-equipped vehicles. Ignition system maintenance and oxygen sensor replacement are the next most significant items. Electrical component failure is the largest source of excessive emissions for fuel-injected vehicles. Oxygen sensor failure is the single greatest source of excessive emissions and ignition system problems are second largest emissions source.

The “Low Emission Vehicle” (LEV) standards adopted by the California Air Resources Board (CARB) require that large-volume manufacturers begin selling electric vehicles in 1998 and that over 99% control of hydrocarbon exhaust emissions be achieved on most other vehicles. When the LEV standards were adopted, the CARB staff estimated that prices for gasoline-fueled cars would increase by $70-170 per vehicle. The price premium for electric cars was estimated to be $1,350. However, a review of detailed information supplied by automobile manufacturers and vendors of emissions control equipment indicates that the actual cost of meeting the LEV standards will be much higher.

The California Bureau of Automotive Repair (BAR) and Sierra Research, Inc. (Sierra) have evaluated a large number of alternative emissions test procedures and developed new procedures that could substantially increase the ability to identify defective vehicles under vehicle inspection and maintenance (I/M) programs. The primary focus of the study was to determine whether an economical “loaded mode” (dynamometer-based) test procedure could be developed that would accurately identify vehicles with emissions in excess of the applicable standards using the Federal Test Procedure (FTP). The results of the BAR/Sierra study show that, using a new “Acceleration Simulation Mode” (ASM) test, 90% of all excess oxides of nitrogen (NOx) emissions can be identified without the use of transient testing or mass emission measurement.

A comprehensive vehicle emission testing program has determined that the California vehicle inspection and maintenance (I/M) program (called “Smog Check”) is reducing emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen from vehicles subject to the program by 12%, 10%, and 4%, respectively. Although substantial, the emission reductions of HC and CO are falling short of the 25% reduction goal set by the Environmental Protection Agency. Reasons for the shortfall include limitations in the ability of idle emission standards to detect defective vehicles; poor quality of visual and functional inspections; and ineffective repair of many failed vehicles. The overriding problem with the program can be summarized as the failure of participating mechanics to identify and correct emissions defects, especially in 1980 and later model vehicles. There are two types of mechanic performance problems which need to be addressed.

Inspection and maintenance (I/M) programs are intended to minimize motor vehicle emissions through the identification and repair of defective vehicles. Laboratory studies have indicated I/M has the potential to reduce hydrocarbon and carbon monoxide emissions by in excess of 25%; however, many of the I/M programs currently operating in the United States may be achieving only minimal emission reductions. In order for the “theoretical” benefits of I/M to be achieved, certain program design features and enforcement procedures are necessary. The important elements of an effective I/M program include stringent emission standards, effective inspection procedures, effective repair requirements, minimal use of waivers, an effective compliance mechanism, reasonable inspection fees, and data analysis and surveillance procedures that identify individuals who are improperly performing inspections and repairs.

A comparison of alternative methods for the control of motor vehicle refueling emissions indicates that Stage II control systems installed at gasoline service stations can provide greater control at lower cost than Onboard control systems installed on motor vehicles. In addition, Stage II control can be achieved with a shorter implementation schedule. Because of this advantage, Stage II controls can achieve more than twice the hydrocarbon reductions possible with Onboard systems during the next ten years, when additional reductions are needed to meet the ambient air quality standard for ozone. Several assumptions are critical to a comparison of Stage II and Onboard controls. These include service station population and size cut-offs, whether “breathing loss” emissions are considered, system cost and lead time, and whether additional evaporative emission controls are considered under both Stage II and Onboard control programs.

Recent tests conducted by the Alaska Department of Environmental Conservation and low ambient temperature tests previously conducted by a variety of other organizations indicate that less progress is being achieved in the control of emissions during cold weather than under temperatures similar to those used during EPA certification testing. Although CO emission standards dropped from 15 grams per mile to 7 grams per mile between 1975 and 1981, far less of a change occurred in CO emissions from new vehicles at 20°F. Cold start CO emissions at 20°F are about 60 grams per mile for late model cars at low mileages. The available test data on these cars seem to indicate that results achieved using the standard emission test procedure are poorly correlated with emissions at lower temperatures. However, the low temperature CO emissions of cars certified at 3.4 grams per mile CO are nearly 502 lower than vehicles certified to a standard of 15 grams per mile.

Programs to control motor vehicle emissions originated in California as a result of Professor A.J. Haagen-Smit of the California Institute of Technology discovering that two invisible automobile emissions, hydrocarbons and oxides of nitrogen, react together in the presence of sunlight to form oxidants such as ozone, a principal ingredient of the infamous Los Angeles area “smog”. The State of California became the first government to regulate the emissions of new automobiles when it adopted requirements for the use of positive crankcase ventilation (PCV) valves beginning with the 1963 model year.

Gasohol, a blend of 90 percent unleaded gasoline and 10 percent ethanol, has been represented as an alternative to pure gasoline which can reduce the nation’s crude oil dependence. However, a systems analysis of the gasohol production processes indicates that gasohol is increasing rather than decreasing the nation’s dependence on crude oil. Alternative uses of the petroleum and natural gas currently used to manufacture ethanol would reduce the nation’s demand for oil. At the present time, every gallon of crude oil “saved” by substituting ethanol for gasoline results in a need to import approximately two gallons of crude oil. The federal government’s claim that gasohol can reduce the nation’s dependence on imported energy appears, to be based principally on political considerations, but also on the assumption that coal will eventually replace the petroleum and natural gas currently used in the gasohol production wherever possible.

A survey of vehicle refueling practices in California during the gasoline shortage of 1979 indicates that the use of leaded gasoline in catalyst equipped vehicles was occurring at a rate of about 1.6%. This 1.6% “misfueling” rate is lower than has been predicted by the U.S. Environmental Protection Agency and is almost exclusively the result of the refueling that occurs at self-service gasoline pumps. About three-quarters of the misfueled vehicles were apparently operated on leaded gasoline routinely. Based on the effect that leaded fuel has on the exhaust emission characteristics of catalyst equipped vehicles it is estimated that misfueling in California is increasing hydrocarbon and carbon monoxide emissions by about 4% and 1.6%, respectively from late model passenger cars.

A fundamental decision to be made in developing a motor vehicle Inspection and Maintenance (I&M) program is whether a “centralized” or “private garage” program will be used. Under the centralized approach, the state or a state contractor operates a network of single purpose “Inspection Centers” to inspect motor vehicles before the completion of the annual registration renewal process. After any repairs necessary to correct vehicles with excessive emissions are made at a facility of the owner's choosing, the vehicle must pass a reinspection at the Inspection Center. Under the private garage (decentralized) approach, both inspections and repairs are conducted by private repair facilities licensed by the state. A comparison of a centralized I&M program and a private garage I&M program currently operating in California indicates that the centralized program is providing over ten times greater emissions reductions.

Data from the Nationwide Personal Transportation Study (NPTS) and other sources have been used to generate distributions of vehicle miles traveled (VMT), average speed, and fuel consumption as a function of trip length. Approximately one third of all automobile travel in the U.S. is seen to consist of trips no more than ten miles in length. Because short trips involve more frequent stops and a smaller percentage of operation during warmed-up conditions, nearly half of the fuel used by automobiles is consumed during the execution of these short trips. The typical trip of approximately ten miles in length has been shown to result in a fuel economy that is equal to the average fuel economy achieved for all trips combined.

The fuel economy data obtained from the emission tests run by the U.S. Environmental Protection Agency (EPA) have been used to show passenger car fuel economy trends from model year 1957 to present. This paper adds the 1975 model year to the historical trend and concentrates on comparisons between the 1975 and 1974 models. Methodologies which allow different 1975 vs 1974 comparisons to be made have been developed. These calculation procedures allow the changes in fuel economy to be determined separately for emission control systems, new engine-vehicle combinations and model mix shifts. Comparisons have been calculated not only for the fleet as a whole but for each of the 13 manufacturers who were certified as of the time this paper was prepared. The net change in fuel economy for the fleet has been estimated at +13.8% comparing the 1975 models to the 1974 models assuming no model mix change occurs.

The use of fuel economy data from the Federal Test Procedure (FTP) has provided a substantial amount of data on the fuel economy of passenger cars in urban driving conditions. Since the FTP does not represent the type of driving done in rural areas, especially on highways, a driving cycle to assess highway fuel economy was a desirable supplement to the FTP. The new Environmental Protection Agency (EPA) “highway” cycle was constructed from actual speed-versus-time traces generated by an instrumented test car driven over a variety of nonurban roads and highways. This cycle reflects the correct proportion of operation on each of the four major types of nonurban roads and preserves the non-steady-state characteristics of real-world driving. The average speed of the cycle is 48.2 mph and the cycle length is 10.2 miles, close to the average nonurban trip length.

This paper discusses some trends and influencing factors in passenger car fuel economy. Fuel economy and fuel consumption were calculated by a carbon balance method from HC, CO, and CO2 emissions measured by the 1972 Federal Test Procedure. The information presented was derived from nearly 4000 tests of passenger cars ranging from 1957 production models to 1975 prototypes. Data are presented for various model year and vehicle weight categories. Trends in fuel economy are discussed on an overall sales-weighted basis and for each individual weight class. Some of the factors that influence fuel economy are quantified through the use of a regression analysis. Particular emphasis is placed on the differences in fuel economy between those vehicles that were subject to federal emission regulations and those vehicles that were not. Three ways to characterize vehicle specific fuel consumption are presented and discussed.