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Measurement of emissions from small utility engines has usually been accomplished using steady-state raw emissions procedures such as SAE Recommended Practice J1088. While raw exhaust measurements have the advantage of producing modal exhaust gas concentration data for design feedback; they are laborious, may influence both engine performance and the emissions themselves, and have no provision for concurrent particulate measurements. It is time to consider a full-dilution procedure similar in principle to automotive and heavy-duty on-highway emission measurement practice, leading to improvements in many of the areas noted above, and generally to much higher confidence in data obtained. When certification and audit of small engine emissions become a reality, a brief dilute exhaust procedure generating only the necessary data will be a tremendous advantage to both manufacturers and regulatory agencies.

Methods for measurement and expression of crankcase or “blowby” emissions from diesels were developed and demonstrated on a test engine. These methods were subsequently used to characterize gas and particulate emissions from two in-service engines. Crankcase emissions were evaluated under engine operating conditions corresponding to the EPA 13-mode certification test. Substances for which analyses were conducted included regulated pollutants, sulfate, trace elements, nitrosamines, individual hydrocarbons, and aldehydes. Emissions from the diesel crankcases were compared to exhaust emissions (where possible) to assess their importance. Analysis for nitrosamines was continued beyond the original effort, utilizing another test engine.

Gaseous and particulate emissions from two heavy-duty diesel engines were characterized while the engines were operated on five different fuels. Characterization included mass rates of major exhaust products, plus analysis of particulate matter for sulfate, trace elements, major elements, total solubles, and other properties. Analysis of rate and composition data was conducted with regard to fuel and engine effects on particulate. Two large particulate samples were also collected for later analysis on groups of organics present.

Emissions from a Stirling engine-powered 1986 model light-duty truck were measured using current EPA (chassis dynamometer) emissions certification procedures and certain specialized tests. Three fuels were used including unleaded gasoline, a blend of MTBE in unleaded gasoline, and JP-4. City (FTP) cycles and Highway (FET) cycles were run on all three fuels, and emissions measured during the cycles included hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). Fuel economy was also calculated for these tests. Additional pollutants measured during some of the tests included aldehydes, 1,3-butadiene, individual hydrocarbon species, and total particulate matter. In addition to the cyclic schedules, steady-state conditions were run on JP-4 and straight gasoline for regulated emissions and fuel economy. The conditions consisted of several simulated gradients at three vehicle speeds, plus idle.

Particulate and gaseous emissions from two light-duty diesel vehicles were measured over eight operating schedules, using five different fuels. Characterization included regulated exhaust emissions and a number of unregulated constituents. Non-routine gas measurements included phenols, hydrocarbon boiling range, and aldehydes. Particulate characterization included mass rates and concentrations, visible smoke, aerodynamic sizing, total organics, BaP, sulfate, phenols, trace elements, and major elements. Statistical analysis of emissions data was undertaken using fuel properties and operating schedule statistics as independent variables. Regressions were computed for a few variables, and analysis of variance and multiple comparisons were used where the data were not suitable for regression analysis.

Exhaust emission data from several fuel effects studies were normalized and subjected to statistical analyses. The goal of this work was to determine whether emission effects of property variation in alternate-source fuels were similar, less pronounced, or more pronounced than the effects of property variation in petroleum fuels. A literature search was conducted, reviewing hundreds of studies and finally selecting nine which dealt with fuel property effects on emissions. From these studies, 15 test cases were reported. Due to the wide variety of vehicles, fuels, test cycles, and measurement techniques used in the studies, a method to relate them all in terms of general trends was developed. Statistics and methods used included bivariate correlation coefficients, regression analysis, scattergrams and goodness-of-fit determinations.

Several properties of a refinery “straightrun kerosene“, which had a narrow boiling range approximating the middle of a No. 1 diesel fuel, were altered to study their effects on regulated and unregulated exhaust emissions. Eleven fuel blends, representing changes in nitrogen content, aromatic level, boiling point distribution, olefin content, and cetane number, were evaluated in a 1975 Mercedes-Benz 240D. Statistical analysis, including regression, was performed using selected fuel properties as independent variables. Higher aromatic levels were generally associated with increased emissions, while increased olefin levels were generally associated with decreased emissions.

A major gap exists in available baseline emissions data on the small utility engine population between the mid-1970's and present day. As part of the input required for a standard-setting process, the California Air Resources Board has funded limited laboratory emission measurements on a number of modern small engines, both 2-stroke and 4-stroke designs. Exhaust constituents characterized in this study include total hydrocarbons, reactive hydrocarbons (RHC), methane, CO, NOx, CO2, O2, aldehydes, and particulate matter. A total of nine engines were evaluated, spanning the range from the smallest widely-used 2-strokes (about 20 cc displacement) to 4-strokes approaching 20 hp.

Emissions from two heavy-duty four stroke direct injection engines designed to use methanol fuel, one using Diesel pilot fuel injection and the other using spark ignition, were characterized in this program along with those from a comparably-sized Diesel engine. Emissions evaluated during both steady-state and transient FTP procedures included regulated gases (HC, CO, and NOx), unburned methanol, aldehydes, other gaseous organics, total particulate, sulfate, soluble organics in particulate and BaP. The engines adapted for methanol fuel and using catalysts emitted less HC, CO, particulate, soluble organics, and BaP than the Diesel fueled engine.

To characterize exhaust emissions from water-cooled 2-stroke outboard motors (the predominant type), four new motors were tested on dynamometer stands. The engines ranged from 4-65 hp in size, and operating conditions were chosen along lines of simulated boat loading. All the measurements were taken at steady-state conditions. Emission concentrations were measured in raw exhaust gas and after the gases had been bubbled through water in a specially constructed tank. Constituents measured included hydrocarbons, CO, CO2, NO, NOx, O2, light hydrocarbons, and aldehydes. Emissions of sulfur oxides (SOx) were estimated on the basis of fuel consumed, and all the exhaust emissions data were used with available information on population and usage of motors to estimate exhaust emission factors and national exhaust emissions impact.

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.

To develop a methodology for characterizing particulate emissions from diesel engines, one 2-stroke cycle engine and one 4-stroke cycle engine were operated in both individual steady-state modes and according to a variation of the 13-mode diesel emissions measurement procedure. Both engines were operated on three fuels, each used with one of two available diesel fuel additives as well as by itself. The primary particulate sampling technique employed was a dilution tunnel, and secondary evaluation techniques included a diluter-sampler developed under contract to EPA by another organization, a light extinction smokemeter, and a filter-type sampling smokemeter. Gaseous emissions were also measured, providing a running check on engine condition. Particulate mass rates were calculated from gravimetric data; and analysis of particulate included determination of sulfur, carbon, hydrogen, nitrogen, phenols, nitrosamines, trace metals, and organic solubles.

Emissions from a modern heavy-duty Diesel truck engine were characterized with five different fuels during transient and steady-state operation. A control fuel (Phillips D-2) was used for baseline emissions, and as base stock in three alternate fuel blends containing EDS or SRC-II middle distillates, or used lubricating oil. The fifth fuel tested was neat soybean oil, heated to 145°C. HC, CO, NOX, and particulate emissions were similar for this engine on all fuels tested, with the exception of higher particulates for the soybean oil and higher NOX for the SRC-II blend.

Three crude shale oils were chosen from six candidates to investigate their possible use as substitutes for No. 2 diesel fuel. Satisfactory hot engine operation was achieved on the crudes using a fuel heating system, allowing emissions characterization during transient and steady-state operation. Regulated gaseous emissions changed little with the crudes compared to diesel fuel; but total particulate and soluble organics increased, and larger injector tip deposits and piston crown erosion were observed. After engine rebuild, two minimally-processed shale oils were run without the fuel heating system, causing no engine problems. Most emissions were higher than for No. 2 fuel using an SO percent distillate of crude shale oil, but lower using a hydrotreated form of the distillate.

Diesel engines are adjusted to manufacturers' specifications when produced and placed in service, but varying degrees of maintenance and wear can cause changes in engine performance and exhaust emissions. Maladjustments were made on two heavy-duty diesel engines typically used in buses in an effort to simulate some degree of wear and/or lack of maintenance. Emissions were characterized over steady-state and transient engine operation, in both baseline and maladjusted configurations. Selected maladjustments of the Cummins VTB-903 substantially increased HC, smoke and particulate emission levels. Maladjustments of the Detroit Diesel 6V-71 coach engine resulted in lower HC and NOX emission levels, but higher CO emissions, smoke, and particulate.

The influence of fuel composition on exhaust emissions from four 1982 model light-duty diesel vehicles was studied on the FTP cycle and at two steady-state conditions, but only the FTP results are presented and discussed in this paper. Nine test fuels were blended specifically for the program, with intentional variation in aromatic content, 90% boiling point, and 10% boiling point. Limited data were also acquired with injection timing at advanced and retarded settings, in addition to the main body of data taken with the engines adjusted to recommended timing. A comparatively small effort was also made to evaluate a tenth fuel consisting of a blend of two of the original nine fuels. Of the fuel characteristics varied intentionally, aromatic content generally had the greatest effect on most emissions of major interest (hydrocarbons, oxides of nitrogen, particulate, soluble organic fraction, polynuclear aromatic hydrocarbons, and mutagenicity of extract by Ames bioassay).

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.

Diesel soot or smoke has been regarded as a nuisance pollutant and potential health hazard, especially in congested urban areas where diesel buses operate. Exhaust emissions from a DDAD 6V-71 coach engine and a similarly-powered 1980 GMC RTS-II coach, fitted with a non-catalyzed particulate trap, were characterized over various Federal Test Procedures for heavy-duty engines, including an experimental test cycle for buses. Regeneration was accomplished using an in-line burner in the exhaust to raise the engines' idle exhaust gas temperature from 120 to 700°C. Trap testing included approximately 15 hours of engine operation and 100 miles of bus operation. Particulate emissions were reduced by an average of 79 percent and smoke emissions were nil using the trap. The effect of the trap on regulated and other unregulated emissions was generally minimal.

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.

In an attempt to characterize emissions from small air-cooled utility engines, five gasoline-fueled models were operated over a variety of speeds and loads, and important exhaust constituents were measured. These emissions included hydrocarbons, CO, CO2, NO, O2, aldehydes, light hydrocarbons, particulates, and smoke. Emissions of SOx were estimated on the basis of the fuel consumed; evaporative losses of hydrocarbons were also estimated. The impact of small engine emissions was calculated on the basis of the test results and information on national engine populations and usage. From these data, it appears that the 50 million or more small engines currently being used account for only a small part of pollutants from all sources.