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A Repeatable Car (REPCA) program has been developed at the Environmental Protection Agency's National Vehicle and Fuel Emissions Laboratory (NVFEL) as part of an ongoing effort to improve the precision of fuel economy and emissions measurements. This concept of using a repeatable car as an integrated system diagnostic tool is not a new idea in the emissions testing field; however, our statistical analyses and organizational approach may be different from what other laboratories are using. Furthermore, given the NVEFL's role in automotive emissions testing, we felt it appropriate to provide related industries a detailed account of our standard laboratory practices, both for informational and comparative purposes. In order to separate vehicle and measurement variability in a relatively simple manner, a process was developed to track REPCA data based on Statistical Process Control principles using the calculation of individual site offset values from two week moving averages.

Several sets of repetitive test data using the 1975 Federal Test Procedure ('75 FTP) have been analyzed to establish the variability of each component measured during each phase of the test. The variability characteristics of four different emission control systems have been discussed and compared. The overall variabilities of the '75 FTP composite values have been assessed at ±6% for hydrocarbons and CO, ±3% for NOx, and ±1% for CO2. The extremely repeatable behavior of the CO2 emissions is utilized to calculate the fuel economy during the test. This calculation is discussed and some fuel economy results from repetitive tests are presented.

The 4000-mile EPA fuel economy figures are presented for passenger cars from pre-emission control models through 1980, for light-trucks from 1975 through 1980, and for motorcycles for 1980. The paper accumulates most of the fuel economy analyses presented in previous papers of this kind. Accordingly, it is voluminous with data, and necessarily terse in textual material. It presupposes reader familiarity with the nature of the EPA tests and data bases, and the techniques used for the analyses, particularly harmonic sales weighting of fuel economy data. The reader must refer to precursor papers for such descriptions. Some aspects treated are: stratification by weight class, vehicle size class, manufacturer, and MPG range; domestic vs. import, gasoline vs. Diesel, and 49-states vs. California models.

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 compiled by the U.S. Environmental Protection Agency (EPA) have been analyzed to determine the trends in passenger car fuel economy beginning with model year 1957. This paper adds the 1976 model year data to the historical trend and concentrates on comparisons between the 1976 and 1975 models. Calculation procedures which allow the changes in fuel economy to be determined separately for system optimization, new engine/vehicle combinations, and model mix shifts have been employed in the analysis which compares 1976 models with 1975 models. A wide range of percentage changes was seen for the fifteen manufacturers who were certified in time to be included in the analysis performed for this paper. The net change in fuel economy for the 1976 new car fleet has been estimated at +12.8% compared to the 1975 new car fleet. System optimization is responsible for 8.8% of the improvement and model mix shifts are projected to account for +3.1% of the change.

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.

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.

Motor vehicles are seldom used in ambient conditions like those defined in current emission regulations. For example, most of the year average temperatures across Europe fall much below the range of legislative testing. Furthermore, it has been widely demonstrated that cold-starts at low ambient temperature increase the emissions. Therefore, there is a growing need to broaden the range of legislative emissions tests and set a separate low-ambient test with respective emission standards. This paper gives emissions test results form a joint research programme between Sweden and Finland. Altogether 11 late model gasoline-fueled TWC vehicles were tested at ambient temperatures of +22 and -7 °C using a variety of different driving cycles. Apart from the driving schedule, other test parameters like vehicle preconditioning, manual vs. automatic transmission and the effect of external cooling were studied and discussed.

This report describes the results of a surveillance study initiated by the U.S. Environmental Protection Agency to measure gaseous exhaust emissions from 1020 light-duty motor vehicles. This project was the second effort in a continuing program using the CVS Federal Test Procedure. Selected privately-owned vehicles, drawn randomly from six metropolitan areas, were tested in as-received condition. The emissions data obtained from these 1966-1972 model-year vehicles are reported in grams per mile of unburned hydrocarbons, carbon monoxide, carbon dioxide and oxides of nitrogen while fuel economy is reported in mpg as determined over the Federal Driving Schedule.

The Environmental Protection Agency (EPA) is developing emission standards for nonroad spark-ignition engines rated over 19 kW. Existing emission standards adopted by the California Air Resources Board for these engines were derived from emission testing with new engines, with an approximate adjustment applied to take deterioration into account. This paper describes subsequent testing with two LPG-fueled engines that had accumulated several thousand hours of operation with closed-loop control and three-way catalysts. These engines were removed from forklift trucks for characterization and optimization of emission levels. Emissions were measured over a wide range of steady-state points and several transient duty cycles. Optimized emission levels from the aged systems were generally below 1.5 g/hp-hr THC+NOx and 10 g/hp-hr CO.

A fleet of 64 heavy-duty 1970-71 model trucks and buses powered by a variety of diesel engines were tested periodically to determine exhaust smoke behavior. Smoke tests were made when the vehicle was new or nearly new and at four month intervals thereafter, or until 160,934 km (100,000 miles) odometer reading was reached. Gaseous emissions of hydrocarbon (HC), carbon monoxide (CO), and nitric oxide (NO) were measured at one point early in the project. Both smoke and gaseous emission tests were performed with chassis versions of the engine dynamometer Federal Test Procedures (FTP). Results in terms of “a” (acceleration), “b” (lugging), and “c” (peak) smoke factors versus mileage are reported for the 13 engine-vehicle-application groupings.

This paper summarizes an investigation of reductions in exhaust emission levels attainable using various techniques appropriate to gasoline engines used in vehicles over 14,000 lbs GVW. Of the eight gasoline engines investigated, two were evaluated parametrically resulting in an oxidation and reduction catalyst “best combination” configuration. Four of the engines were evaluated in an EGR plus oxidation catalyst configuration, and two involved only baseline tests. Test procedures used in evaluating the six “best combination” configurations include: three engine emission test procedures using an engine dynamometer, a determination of vehicle driveability, and two vehicle emission test procedures using a chassis dynamometer. Dramatic reductions in emissions were attained with the catalyst “best combination” configurations. Engine durability, however, was not investigated.

Evaporative emission tests were performed on forty in-use late model passenger cars using different volatility fuels and varying temperatures. Results show that diurnal and hot soak emissions are quite sensitive to temperature, and also that the temperature sensitivity increases with the use of higher volatility fuels. Empirical models were developed to express diurnal and hot soak emissions as a function of fuel volatility and temperature.

Of all existing modes of transportation, onroad motor vehicles are the largest contributor to greenhouse gas emissions and fuel usage. The Environmental Protection Agency and the National Highway Traffic Safety Administration finalized regulations in April 2010 to reduce greenhouse gas emissions and improve fuel economy for 2012-2016 model year light-duty vehicles. In November 2010, both agencies jointly proposed the first ever greenhouse gas standards for medium- and heavy-duty trucks which are expected to take effect for model years starting in 2014. Vehicles of light-duty families are subject to mandatory testing for certification and compliance. Unlike the light-duty sector where a vast majority of vehicles are mass produced for generally similar purposes, medium- and heavy-duty vehicles are commonly custom-made.