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The use of diesel exhaust-emissions measurements to predict the observed odor from diesel engine exhaust has been studied, using a group of 31 trucks and buses powered by a variety of diesel engines. Regression analysis of gaseous emissions at a variety of conditions has resulted in equations for use in predicting odor. Acrolein, carbon dioxide, total hydrocarbons, selected light hydrocarbons, nitric oxide, carbon monoxide, and aliphatic aldehydes have been related to perceived odor. Some of these exhaust products are odorous and some are nonodorous yet indicative of the completeness of combustion. The empirical method, however, is somewhat less reliable than the observed odor based on a trained panel rating supra-threshold levels in terms of the PHS Quality-Intensity Odor Rating kit. In general, the greater variety of measurements and the fewer type of engines will increase odor prediction accuracy.

The research program on which this paper is based included both laboratory emission measurements and extrapolation of results to the national population of heavy-duty farm, construction, and industrial engines. Emission tests were made on four gasoline engines and eight diesel engines typical of those used in F, C, and I equipment. Gaseous and particulate emissions were measured during engine operation on well-accepted steady-state procedures, and diesel smoke was measured during both steady-state conditions and the Federal smoke test cycle. Emissions measured were hydrocarbons, CO, CO2, NO, NOx, O2, aliphatic aldehydes, light hydrocarbons, particulate, and smoke. Emission of sulfur oxides (SOx) was estimated on the basis of fuel consumed, and both evaporative and blowby hydrocarbons were also estimated where applicable (gasoline engines only). Data on emissions obtained from this study were compared with those available in the literature, where possible.

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.

This is a summary compilation and analysis of exhaust-emission results and operating parameters from forty-five heavy-duty gasoline and diesel-powered vehicles tested over a 7.24-mile road course known as the San Antonio Road Route (SARR); and, for correlative purposes, on a chassis dynamometer.(2) Exhaust samples were collected and analyzed using the Constant Volume Sampler (CVS) technique similar to that used in emission testing of light-duty vehicles. On the road course, all equipment and instrumentation were located on the vehicle while electrical power was supplied by a trailer-mounted generator. In addition to exhaust emissions, operating parameters such as vehicle speed, engine speed, manifold vacuum, and transmission gear were simultaneously measured and recorded on magnetic tape. The forty-five vehicles tested represent various model years, GVW ratings, and engine types and sizes.

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 describes the results of a public opinion survey on testing of diesel exhaust odors conducted during 1969 and 1970. Major goals of the research were to relate public opinion of the odors and the objectionability associated with them to odor intensity, and to obtain a dose-response curve as the primary result. The dose-response curve was needed to assess odor-control technology by providing a criterion for deciding whether or not the effect of a given control item would be noticed by the general public, reduce complaints, or be worth the cost and effort required for its implementation. The engine used as the live odor source for the subject research was a two-stroke cycle type similar to those used in many buses. This engine type was chosen because its exposure to the public in urban bus applications is very widespread, and because a large portion of the Environmental Protection Agency's odor research had been performed with similar engines.

Seven motorcycles, ranging in size from 100 to 1200 cm3, were tested for emissions characterization purposes. They were operated on the federal seven-mode test procedure (for 1971 and older light-duty vehicles), the federal LA-4 test procedure (for 1972 and later LDVs), and under a variety of steady-state conditions. Four of the machines tested had 4-stroke engines, and the other three had 2-stroke engines. Emissions which were measured included hydrocarbons, CO, CO2, NO, NOx, O2, aldehydes, light hydrocarbons, particulates, and smoke. Emissions of SOx were estimated on the basis of fuel consumed, and evaporative hydrocarbon losses were also estimated. Crankcase “blowby” emissions from one 4-stroke machine were measured. The impact of motorcycles on national pollutant totals was estimated, based on the test results and information from a variety of sources on national population and usage of motorcycles.

This paper describes a research program on exhaust emissions from snowmobile engines, including both emissions characterization and estimation of national emissions impact. Tests were conducted on three popular 2-stroke twins and on one rotary (Wankel) engine. Emissions that were measured included total hydrocarbons, (paraffinic) hydrocarbons by NDIR, CO, CO2, NO (by two methods), NOx, O2, aldehydes, light hydrocarbons, particulate, and smoke. Emissions of SOx were estimated on the basis of fuel consumed, and evaporative hydrocarbons were projected to be negligible for actual snowmobile operation. During emissions tests, intake air temperature was controlled to approximately -7°C (20°F), and room air at approximately 24°C (75°F) was used for engine cooling. Based on test results and the best snowmobile population and usage data available, impact of snowmobile emissions on a national scale was computed to be minimal.

Five light-duty vehicles were used to investigate HC, CO, and NOx emissions and fuel economy sensitivity to changes in the length of soak period preceding the EPA Urban Dynamometer Driving Schedule (UDDS). Emission tests were conducted following soak periods 10 minutes to 36 hours in length. Each of the first 8 minutes of the driving cycle was studied separately to observe vehicle warm-up. Several engine and fuel system temperatures were monitored during soak and run periods and example trends are illustrated. The extent to which emission rates and fuel consumption are affected by soak period length is discussed.

A program of research on diesel smoke and odor was sponsored by the U.S. Public Health Service by contract with Southwest Research Institute. A test facility was developed in which full-scale trucks and buses were operated on a chassis dynamometer through operating modes that yielded maximum exhaust smoke and odor. A system of exhaust dilution was employed to provide realistic odor concentrations to a panel of judges who rated the intensity and quality of the exhaust in terms of a set of chemical standards. Smoke levels were measured with a PHS-designed full-flow optical smokemeter. After an initial baseline evaluation of groups of buses and trucks with standard engines, various control techniques were evaluated to determine their effectiveness in reducing smoke and/or odor. Chemical analyses of the exhaust were made for the purpose of correlating the smoke and odor reductions with changes in exhaust composition.

Exhaust emissions from heavy duty gasoline-powered vehicles have been studied in detail, under NAPCA support, at South west Research Institute. The principal exhaust emissions studied were carbon monoxide, hydrocarbons, and oxides of nitrogen. A broad variety of vehicles was tested with three variable speed experimental procedures using chassis dynamometers to simulate actual road operations. Approximately 150 trucks and buses of all weight classes were investigated to determine the ability of each vehicle to perform with the respective experimental cycle, each vehicle’s contribution of contaminants on a mass basis per mile driven, and the applicability of these cyclic test procedures for federal testing.

The advent of diesel-powered versions of production passenger cars signals significant dieselization in the United States. Two vehicles, an experimental Oldsmobile diesel Cutlass and a Volkswagen diesel-powered Rabbit, were evaluated to determine their gaseous, particulate, smoke, odor, and noise emissions. For comparison, a 1977 Oldsmobile Cutlass powered by the 260 CID gasoline engine and a 1.6 liter gasoline fuel injected Volkswagen Rabbit (Calfornia version) were similarly evaluated under most emission categories. Three transient driving cycles were employed including those used in emissions certification, sulfate testing, and highway fuel economy.

A wide variety of exhaust emissions are reported for three diesel engines typically used in heavy-duty intercity truck and intracity bus operation. Particulate, odor, sulfate, sulfur dioxide, and selected non-reactive hydrocarbons were measured in addition to the regulated pollutants from Detroit Diesel 6V-7l and 8V-7lTA engines and a turbocharged Cummins 855 cu in research engine. The 855-TC engine was run in standard and a variable injection timing configuration, while the 6V-7l city bus engine was run with two types of injector designs. Emission rates are summarized in terms of grams per unit of fuel consumed and per unit of power output. The data allows direct comparison between engines and engine configurations, as well as a function of engine speed and load condition.

Diesel-powered cars afford some distinct advantages in fuel economy and certain exhaust emissions relative to the conventional Otto cycle engine. Particulate and sulfate emissions from light-duty diesels are two important unregulated emissions for which little is known. Five diesel-powered, light-duty vehicles, a Peugeot 204D, a Mercedes 240D, a Mercedes 300D, a Comprex-equipped Mercedes 220D, and a Perkins 6-247 powered IH pickup, were used to quantify the range of particulate, sulfate as well as other unregulated emissions of odor, visible smoke, sulfur dioxide, aldehydes, and selected non-reactive hydrocarbons. Three transient driving cycles were employed including that used in emissions certification, sulfate testing, and highway fuel economy. Emission rates of particulate, sulfate, and other contaminants of a regulated and unregulated nature are presented in several ways: mass per unit of time, per unit of fuel consumed, and per unit of distance driven.

Exhaust emissions from in-use diesel trucks and buses can be reduced by application of retrofits consisting of new parts and adjustments. The results of fleet test demonstrations of two retrofit kits, one for 2-stroke diesel-powered buses and the other for 4-stroke diesel trucks, are described. Except for the catalytic muffler, the components and adjustments composing the General Motors environmental improvement proposal kit for General Motors city buses were found helpful in reducing exhaust odor, smoke, and certain gaseous emissions. The turbocharger kit and adjustments marketed by Cummins Engine for its NHC 250, an in-use naturally aspirated truck engine, was likewise found to reduce visible smoke satisfactorily. The fleet test data are from three city buses operated for two years and three intercity truck tractors operated for eight months.