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The paper presents emissions data obtained from three 4-stroke lawn mower engines that were tested using three test cycles: a six mode steady-state test, a quasi-steady-state test, and a transient test. A comparison of emissions from the three test cycles is made for non-methane organic gases, carbon monoxide, nitrogen oxides, detailed hydrocarbons (percent of total organic emissions that are paraffin, olefin, aromatic, or acetylene), and toxic compounds (benzene, 1,3-butadiene, formaldehyde, and acetaldehyde). Differences in ozone potential are also determined and reported for each test cycle. The engines tested are all unregulated (not certified to any emission standard), in-use engines that have a wide range of emission rates. Results indicate that hydrocarbon emission rates are statistically higher with the transient test cycle compared to the steady-state test.

Smog chamber tests were conducted using automobile exhaust gas generated during emission tests with a group of alternatively fueled vehicles. The tests were designed to evaluate the photochemical characteristics of organic emissions from vehicles operating on compressed natural gas, methanol, ethanol, liquefied petroleum gas, and reformulated gasolines. A description of the emission characterization portion of the study is presented in this paper to assist in better understanding the chamber experiments described in a companion paper. The study is part of a larger program in which the U.S. Department of Energy (DOE), in cooperation with the U. S. Environmental Protection Agency (EPA), is examining the effects of alternative fuel usage on emissions and fuel economy.

This paper describes an emissions study of two vans powered by compressed natural gas (CNG). One van was relatively new, while the other had been driven more than 120,000 mi. The purpose of the study was to obtain emissions information which could be used to predict the impact of CNG use on ambient air quality and air toxic concentrations, and to develop a better understanding of the effect of ambient temperature variations on CNG emissions. Using four different driving cycles, emission tests were carried out at 20°F, 75°F, and 105°F. Test results agree with previous findings that document low emissions of nonmethane hydrocarbons from CNG vehicles. Results also confirm the expectation that CNG emissions are not significantly affected by ambient temperature variations, although an increase in formaldehyde emission was noted for the 20°F cold-start tests.

Exhaust emissions from a diesel passenger car were characterized and measured to examine the effect of ambient temperature on emissions performance. The vehicle was tested at three temperatures on a chassis dynamometer located within a cold cell. Three driving cycles and three fuels of varying quality were used. The effort included measurements of regulated exhaust gases and particles, particulate organic fractions and their molecular-weight distributions, particulate fractions under 2 microns in diameter, trace metal contents, and fuel economy. Results indicate that reductions in ambient temperature had little effect on emissions or fuel economy in this study. In some cases, statistically significant increases in NOx emissions were measured with decreases in ambient test temperature. Other differences related to temperature effects occurred more frequently with the lower quality fuels.

A minicomputer controlled automotive emissions sampling and analysis system (the Real-Time System) was developed to determine vehicular modal emissions over various test cycles. This data acquisition system can sample real-time emissions at a rate of 10 samples/s. A buffer utilization program enables incoming digital data from an entire test sequence to be logged rapidly and stored on disc, this permitting the user to reaccess the data at later dates for processing in accordance with modal schemes.