The Effects of Oxygen-Enriched Intake Air on FFV Exhaust Emissions Using M85 961171
This paper presents the results of emission tests of a flexible fuel vehicle (FFV) powered by an SI engine, fueled by M85, and supplied with oxygen-enriched intake air containing nominal 21%, 23%, and 25% oxygen (by volume). Emission data were collected by following the standard federal test procedure (FTP) and U.S. Environmental Protection Agency's (EPA's) “off-cycle” test EPA-REP05. Engine-out total hydrocarbons (THCs) and unburned methanol were considerably reduced in the entire FTP cycle when the oxygen content of the intake air was either 23% or 25%. However, CO emissions did not vary appreciably, and NOx emissions were higher. Formaldehyde emissions were reduced by about 53% in bag 1, 84% in bag 2, and 59% in bag 3 of the FTP cycle when 25% oxygen-enriched intake air was used. During the cold-phase FTP, reductions of about 42% in THCs, 40% in unburned methanol, 60% in nonmethane hydrocarbons (NMHCs), and 45% in nonmethane organic gases (NMOGs) were observed when 25% oxygen-enriched intake air was used. The corresponding NOx emissions increased by about 78%. In general, converter-out emissions obtained were also reduced when oxygen-enriched intake air was used, but to a lesser degree. Off-cycle, bag 3 converter-out emissions were reduced when 23% oxygen-enriched intake air was used; CO emissions were reduced by about 67%, and THCs were reduced by about 52%. The FFVs operating on M85 that use 25% oxygen-enriched intake air during only the initial 127 s of the cold-phase FTP or that use 23% or 25% oxygen-enriched intake air during only the cold-phase FIP can meet (without adjusting for catalyst deterioration factors) the reactivity-adjusted NMOG, CO, NOx, and formaldehyde emission standards of the transitional low-emission vehicle (TLEV).