Emissions from 4-Cycle Walk-Behind-Mower Engines: Test Cycle Effects 972793

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. Overall, regulated emission rate differences due to test cycle are fairly small with no difference exceeding 20 percent Unregulated emission rates and organic composition, except for carbon dioxide, appear not particularly sensitive to test cycle selection.