Characterization of Emissions from Malfunctioning Vehicles Fueled with Oxygenated Gasoline-MTBE Fuel — Part I Fred Stump, Silvestre Tejada, and David Dropkin National Exposure Research Laboratory U. S. Environmental Protection Agency Research Triangle Park, NC 27711 Colleen Loomis Clean Air Vehicle Technology Center, Inc. Research Triangle Park, NC 27709 ------- Table of Contents Abstract ii List of Tables iii List of Figures iv Abbreviations and Symbols v INTRODUCTION 1 EXPERIMENTAL METHODS AND MATERIALS 2 Test Fuels 2 Test Schedule/Conditions 2 Test Vehicles 3 Test Facilities 3 Test Procedures 4 Tailpipe Emissions 5 RESULTS AND DISCUSSION 5 Regulated Emissions 8 Toxic Emissions 12 Particulate Emissions 13 SUMMARY AND CONCLUSIONS 17 ACKNOWLEDGMENTS 19 DISCLAIMER 20 REFERENCES 20 l ------- ABSTRACT Two vehicles, a 1993 4-cyUnder Chevrolet Cavalier and a 1993 6-cylinder Ford Taurus, were tested using three different fuels - a winter grade fuel containing 11.3% methyl tertiary butyl ether (MTBE), a winter grade fuel (base fuel) without MTBE, and a summer grade fuel without MTBE. Vehicle tests were conducted at ambient temperatures of 75°( with summer grade fuel only), 20°, 0°, and -20°F. The vehicles were first tested under a normal mode (vehicles were tuned to manufacturers specifications) and then tested under two simulated malfunction modes - 1) the oxygen (02) sensor was disconnected and 2) the exhaust gas recirculating valve (EGR) was disconnected and plugged. The malfunction modes were not tested simultaneously. The vehicles were tested on the Urban Dynamometer Driving Schedule (IJDDS) of the Federal T est Procedure (FTP). Two high speed REP05 test cycles were run after each of the IJDDS tests. The exhaust emissions determined were particulate matter (PM2.5 and PM10), gaseous total hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx), speciated (individual) hydrocarbons, MTBE, and speciated aldehydes. The IJDDS hydrocarbon emissions from both vehicles increased as test temperatures decreased. Under normal mode, the HC emissions at 20°F tripled, the CO emissions more than doubled, while the NOx changed only slightly when the vehicles were tested at -20°F. HC emissions with the MTBE fuel were on the average 9-14% less than those with the base fuel. The Cavalier emitted on the average 12% less CO with the MTBE fuel than with the base fuel while the Taurus, 5% more CO with the MTBE fuel. The Cavalier HC, CO, and NOx emissions on the average increased 235%, 489% and -8%, respectively with the base fuel and 226%, 483%) and -27%, respectively with the MTBE fuel over the normal mode emissions when the oxygen sensor was disconnected at the winter test temperatures. The Taurus HC, CO, and NOx emissions on the average increased 216%>, 347%) and 55% with the base fuel and 91%>, 138%> and 52% respectively with the MTBE fuel. Disconnecting the EGR had a minimal impact on the HC and CO emissions but a significant one on NOx emissions. The Cavalier NOx emissions increased 81% and 148% with the base and MTBE fuel respectively over those of the normal mode, while those of the Taurus increased 31 % and 41%> respectively. The emissions of such toxic compounds benzene and 1,3-butadiene tended to increase as the testing temperature decreased. Disconnecting the 02 sensor generally increased the emissions of the toxic compounds, while the fuel containing MTBE reduced some toxic compound emissions. The measured emissions of formaldehyde and acetaldehyde did not show trend associated with changes of test temperatures, modes or fuels used in this study. Particulate emissions were mostly PM2.5 particles. Particulate emissions correlated very well (R2 > 0 .920) with HC emissions for every vehicle-fuel-malfunction mode combinations. Particle emissions increased 4-5 times when the test temperature was decreased from 20°F to -20°F. Both vehicles emitted more particles with the base fuel than with the MTBE at all test conditions. Taurus particle emissions ranged 13-73 mg/mi with the base fuel and 6-34 mg/mi with the MTBE fuel. The Taurus particulate emissions were 2-3 times greater than those of the Cavalier. Maximum particulate emissions were obtained when the oxygen sensor was disconnected. Particle emissions with a disconnected EGR differed only slightly from normal mode emissions for both vehicles. u ------- List of Tables Table 1 Characteristics of test fuels 2 Table 2 Test Schedule/Conditions for 1993 Chevrolet Cavalier and Ford Taurus vehicles . . 3 Table 2a Vehicles tested 3 Table 3 Vehicle tailpipe emissions rates at 75°F with summer grade fuel 5 Table 4 Vehicle UDDS tailpipe emissions at 20°F 6 Table 5 Vehicle UDDS tailpipe emission rates at 20°F 6 Table 6 Vehicle UDDS tailpipe emission rates at -20°F 7 Table 7 Vehicle REP05 tailpipe emission rates 7 in ------- List of Figures Figure 1 Correlation plots of benzene vs HC as a function of fuel 12 Figure 2 Correlation plots of PM10 and PM2.5 particulate emissions from all vehicle-fuel-mode combinations at all test temperatures 13 Figure 3 Correlation plots of PM2.5 vs HC as a function of fuel and oxygen sensor malfunction 14 Figure 4 Correlation plots of PM2.5 vs HC as function a function of fuel and EGR malfunction 15 Figure 5 Correlation plots of REP05 PM2.5 vs HC a function of fuel and oxygen sensor malfunction 16 Figure 6 Correlation plots of PM2.5 vs HC as a function of fuel and EGR malfunction . . . 17 iv ------- Abbreviations and Symbols °F Degree Fahrenheit AME Archived Mobile Source Emissions Data Base CFR Code of Federal Regulations CO Carbon monoxide CVS Constant Volume Sampler EGR Exhaust Gas Recirculation valve FI Fuel Injection FTP Federal Test Procedure g/cm3 gram per cubic centimeter g/mi gram per mile GC-MS Gas chromatography - mass spectrometry HC Hydrocarbon IBP Initial Boiling Point LA-4 Los Angeles cycle, corresponding to stabilized cold cycle of UDDS mg microgram mg/mi milligram per mile mph/sec Miles per hour per second MTBE Methyltertiarybutylether NC North Carolina NOx Oxide of nitrogen 02 oxygen 02 S Oxygen sensor R2 Correlation coefficient REP05 A high speed, high acceleration driving cycle RVP Reid Vapor Pressure TWC Three Way Catalyst v ------- INTRODUCTION Motor vehicles emit large quantities of hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NOx). These emissions participate in the atmospheric photochemical processes to form ozone and other oxidants. Motor vehicles also emit toxic compounds such as formaldehyde, acetaldehyde, benzene, 1,3-butadiene and particulate matter (PM2.5 and PM 10). The 1990 Clean Air Act Amendment specify a reduction in these toxic emissions.1 This study characterized the emissions from two recent model light duty gasoline-powered vehicles tested at ambient temperatures of 75°, 20°, 0°, and -20°F with the vehicles normally tuned to manufacturers' specifications using three commercially available fuels - a winter grade fuel without MTBE, a winter grade fuel with MTBE, and a summer grade fuel without MTBE. In addition, the two vehicle were tested using the same fuel and temperature combinations as the normal mode under two distinct simulated malfunction modes - 1) the 02 sensor was disconnected and 2) the EGR valve was disconnected and plugged. Particulate emissions are becoming of major concern due to their adverse effects on materials, visibility reduction, atmospheric reactivity, and human health. Recent epidemiological studies have indicated health concerns for particulate matter emissions with an aerodynamic diameter of 10 //m or less.2'3 In this study, individual PM2.5 and PM 10 filters were taken from each of the UDDS tests (duplicate tests at each condition). After the completion of each UDDS test, the particulate emissions from two REP05 driving cycles were collected on individual PM2.5 and PM 10 filters. Currently there is little research information regarding particulate emission rates from recent model in-use light-duty gasoline vehicles4 and very few studies have been reported on vehicles tested at malfunction conditions at various ambient temperatures. 1 ------- EXPERIMENTAL METHODS AND MATERIALS The test fuels, vehicles, facilities, and procedures are described in this section. Test Fuels The fuels used in this study were a summer grade fuel, a winter grade fuel containing no methyl tertiary-butyl ether (MTBE), and a winter grade fuel containing 11.3% (volume) MTBE. These fuels were purchased locally and are representative of the fuel in-use. The test fuels are listed in Table 1. Table 1. Characteristics of test fuels. Fuel Property Summer Winter Winter-MTBE Specific gravity, g/cm RVPa Distillation, °F IBP 10% 50% 90% End Point Paraffins, % Olefins, % Aromatics, % Benzene, % MTBE, % a Reid vapor pressure 0.75 6.87 102 133 219 351 421 45.43 14.08 40.23 1.23 0.38 0.75 9.72 101 131 219 355 425 55.33 15.89 28.61 1.23 0 0.72 14.78 77 100 173 314 432 62.09 12.85 24.79 0.63 11.3 Test Schedule/Conditions A single UDDS test was performed with each vehicle at 75 °F with the summer grade fuel at each test mode. Duplicate UDDS tests at 20, 0 and -20°F at each test mode were performed with each of the winter grade fuels (Table 2). Each UDDS test was followed by two consecutive REP05 tests. The vehicles were conditioned with each test fuel at each test condition before actually testing the vehicle for data collection. The vehicles were conditioned each day by running an LA-4 driving cycle after completion of the high speed REP05 tests. 2 ------- Table 2. Test Schedule/Conditions for 1993 Chevrolet Cavalier and 1993 Ford Taurus vehicles. Description Summer Test Conditions Winter Test Conditions Driving Cycles Test Temperature Duplicate Runs Fuel Type MTBE Malfunction Modes Emissions Measured: IJDDS 75°F Single test only Summer Fuel Without 02 and EGR Gaseous Emissions No Particles IJDDS + 2 REP05 20, 0, -20°F. Duplicate runs Winter Fuel With and Without 02 and EGR Gaseous Emissions Particle Measured: PM2.5 and PM10 Test V ehicles The vehicles used in this study are described in Table 2a. Table 2a. Vehicles tested. Vehicle Cyl. Vehicle Displaced Fuel Emission Miles Liters System System1 1993 Chevrolet Cavalier 4 9545 2.2 FI* EGR/TWC/02S 1993 Ford Taurus 6 5320 3 FI EGR/TWC/02S ^ EGR _ Exhaust Gas Recirculation, TWC ~~ Three Way Catalyst, 02S ~~ Oxygen Sensor * FI _ Fuel Injeetion Test Facilities Vehicle road simulations were conducted on a Horiba Model CDC800/DM A915 computerized DC electric chassis dynamometer. The dynamometer was housed in a temperature controlled chamber capable of maintaining vehicle test temperatures from -20° to 110°F. Vehicle emissions were transferred from the vehicle tailpipe to a constant volume sampling 3 ------- (CVS) system through a 7.62-cm i.d. (3 inch) section of flexible stainless steel tubing heated to 230°F. The CVS system, which dilutes the tailpipe emissions with charcoal-filtered room air, has been described previously.5 A heater has been added behind the dilution air filter to raise the tunnel dilution air temperature to 150°F to prevent formaldehyde and other compound losses in the system.6 Test Procedures Emission tests were conducted in close accord with the Code of Federal Regulations (CFR) Title 407 using the Urban Dynamometer Driving Schedule (UDDS) and a high speed, high acceleration rate "off-cycle" sequence (REP05). The UDDS cycle has a maximum speed of about 57 mph, a maximum acceleration rate of about 3.3 mph/sec, and an average speed of about 19.6 mph. The cycle includes three phases: a cold start transient phase (505 sec), a stabilized phase (808 sec), and a hot start transient phase (505) with a 10 minute engine-off soak between phases two and three. The REP05 cycle has a maximum speed of about 80 mph, a maximum acceleration rate of about 8.5 mph/sec, and an average speed of about 51.5 mph. It includes two test phases: a high speed driving mode (1195 sec) and a final high acceleration rate mode (205 sec). At the beginning of the test week, the vehicle to be tested was pre-conditioned by driving the vehicle over the UDDS cycle with the test fuel, in the test mode, and at the test temperature to be used for data collection. The daily UDDS test served (as duplicates were run at all temperatures except 75 °F) as the pre-conditioning for the actual test. During the test week when the vehicle, fuel, temperature, or mode were to be changed, the vehicle was conditioned in the afternoon after the daily test was over, by running an LA-4 cycle (phase one and phase two of the UDDS cycle) at the test conditions to be used the following day. Each UDDS test cycle was followed by two REP05s. Particulate PM2.5 and PM 10 emissions from a single UDDS cycle were each collected on single filters using a PM2.5 and a PM 10 cyclone system (University Research Glassware, Carrboro, NC). Single filters were used to collect the PM2.5 and PM 10 emissions from two consecutive REP05 cycles. Vehicle emissions were measured at 75°, 20°, 0°, and -20 °F for each of the UDDS driving cycles and the REP05 high speed cycles. No REP05 particulate filter data were obtained at 75°F due to equipment problems. Integrated emission samples were collected from the CVS system in Tedlar bags for each UDDS test phase including the initial 124 seconds of phase one. Also, a background air sample was taken after the charcoal dilution air filter. The regulated emissions (HC, CO, and NOx) were measured in real time with instruments connected to the CVS system. Vehicle emissions were characterized to determine speciated (individual) hydrocarbons, speciated aldehydes, regulated gaseous emissions, and MTBE. Identification or structural formulas for more than 95% of the emitted HCs have been determined by established gas chromatographic-mass spectrometric (GC-MS) techniques. Supplementary emission data of regulated, unregulated, speciated HCs, aldehydes, and MTBE are available from the authors. 4 ------- Tailpipe Emissions The vehicle UDDS bag samples were analyzed for speciated hydrocarbons and MTBE by gas chromatography. Data were manually transferred to a PC where peak assignments were made using a Lotus 1-2-3 program developed for identifying compounds in complex chromatograms8. The data were finally transferred to the Archived Mobile Source Emissions Data Base (AME). The concentrations of the regulated emissions were reported as g/mi and mg/mi for individual HCs, aldehydes, and MTBE. Aldehyde emissions were sampled from the CVS system through a heated (212°F) stainless steel line and collected on silica gel cartridges coated with acidified 2.4-dinitrophenylhydrazine. A mass flow controller was used to regulate the sampling rate of the aldehydes in the exhaust stream at 1 L/min. The aldehydes were analyses previously described liquid chromatographic procedures.9 Particle mass was determined by weighing the filter before and after sample collection in an electronic balance with mass resolution of ±1 jig. All filter samples were equilibrated for 24 hours in a constant humidity room prior to weighing. RESULTS AND DISCUSSION Single UDDS test was performed with each vehicle at 75°F with the summer grade fuel at each test mode. Duplicate UDDS tests were performed at 20°F, 0°F, and -20°F with each of the winter grade fuel at each test mode. The individual UDDS test with the winter grade fuel was followed by two consecutive REP05 tests. The data were not statistically evaluated since only- single and duplicate tests were made. Any comparison should be viewed from this perspective. The THC emission results reported were the values determined by the analytical bench and total hydrocarbon analyzer (using the flame ionization detector) rather than a summation of the Table 3. Vehicle tailpipe emission rates at 75°F with summer grade fuel. Vehicle Cavalier Taurus Mode No 02 Sensor EGR No 02 Sensor EGR Malfunction Disconnected Disconnected Malfunction Disconnected Disconnected Fuel, Summer Grade THC, g/mi 0.19 1.71 0.19 0.3 0.67 0.24 CO, g/mi 4.51 48.71 3.27 4.58 11.61 3.95 NOx, g/mi 0.69 1.16 2 0.59 1.69 0.82 MTBE, mg/mi NA+ NA NA NA NA NA Formaldehyde, mg/mi 0.9 1.17 1.36 0.76 1.33 0.81 Acetaldehyde, mg/mi 1.37 2.84 1.29 0.57 1.18 0.61 Total Aldehydes, mg/mi 3.42 5.64 3.93 2.63 4.27 2.4 Benzene, mg/mi 16.3 106.94 11.07 8.07 45.5 7.69 1,3-Butadiene, mg/mi 0.64 2.82 0.03 1.21 0.20 0.77 ^ Data not available 5 ------- Table 4. Vehicle UDDS tailpipe emissions at 20°F. Vehicle Cavalier Taurus Mode No 02 Sensor EGR No 02 Sensor EGR Malfunction Disconnected Disconnected Malfunction Disconnected Disconnected Fuel Base* MTBE* Base MTBE Base MTBE Base MTBE Base MTBE Base MTBE THC, g/mi 0.49 0.46 2.43 2.08 0.66 0.49 0.62 0.46 1.93 0.8 0.64 0.44 CO, g/mi 10.35 10.63 94.39 77.38 12.75 11.14 6.94 6.1 28.45 11.42 7.64 6.86 NOx, g/mi 0.55 0.64 0.52 0.7 1.61 1.83 0.73 0.45 0.98 1.49 0.91 0.67 MTBE, mg/mi NA 5.12 NA 8.68 NA 5.42 NA 15.49 NA 12.05 NA 11.63 Formaldehyde, mg/mi 7.6 2.7 3.79 5.94 3.25 7.27 1.57 2.2 2.45 2.19 2.37 2.67 Acetaldehyde, mg/mi 4.55 1.27 7.25 6.94 1.45 3.64 1.1 1.12 1.97 1.22 1.37 1.38 Total Aldehydes, mg/mi 18.93 5.25 20.15 17.52 7.25 10.18 4.24 4.77 7.41 6.4 6.19 7.13 Benzene, mg/mi 23.08 16.12 86.64 62.84 30.71 17.3 25.72 8.56 64.2 28.15 35.12 8.69 1,3-Butadiene, mg/mi 0.7 3.36 7.48 5.82 1.69 1.48 2.78 2.12 9.91 2.48 4.32 1.94 PM2.5, mg/mi 3.58 3.99 7.38 4.72 7.31 4.61 12.7 6.22 15.97 6.74 17.37 7.05 PM10, mg/mi 3.99 4.56 7.21 5.44 8.04 4.46 12.5 5.7 15.35 7.31 17.52 7.05 ^ Winter grade fuel without MTBE, ^ Winter grade fuel with MTBE Table 5. Vehicle UDDS tailpipe emission rates at 0°F. Vehicle Cavalier Taurus Mode No 02 Sensor EGR No 02 Sensor EGR Malfunction Disconnected Disconnected Malfunction Disconnected Disconnected Fuel Base* MTBE* Base MTBE Base MTBE Base MTBE Base MTBE Base MTBE THC, g/mi 1.05 0.92 3.03 2.65 1.15 0.94 0.91 0.81 2.71 1.73 1.17 0.86 CO, g/mi 24.58 19.71 120.9 100.3 25.17 18.95 8.91 9.96 39.96 24.73 10.09 9.92 NOx, g/mi 0.61 1.23 0.47 0.54 0.86 1.86 0.56 0.47 0.94 0.97 0.87 0.73 MTBE, mg/mi NA 20.46 NA 27.42 NA 19.92 NA 34.58 NA 39.01 NA 34.33 Formaldehyde, mg/mi 4.08 4.16 3.66 7.42 4.01 3.91 3.23 3.72 4.72 4.22 4.36 4.2 Acetaldehyde, mg/mi 2.09 1.99 7.42 4.88 2.2 2.05 1.44 1.55 3.25 2.3 1.3 1.59 Total Aldehydes, mg/mi 8.43 9.99 20.4 14.89 8.87 8.74 6.89 9.21 12.69 10.76 8.35 8.63 Benzene, mg/mi 49.05 22.19 109.5 74.12 50.55 22.06 29.81 21.1 73.14 60.22 24.82 22.19 1,3-Butadiene, mg/mi 3.29 2.7 15.07 6.92 3.89 2.7 4.93 4.34 12.74 9.88 4.51 4.14 PM2.5, mg/mi 14.1 9.12 16.59 10.52 13.79 8.4 28.62 16.8 31.63 18.1 40.7 19.86 PM10, mg/mi 12.34 9.96 16.28 11.61 12.44 9.12 27.74 17.6 32.72 19.86 36.66 19.08 ^ Winter grade fuel without MTBE, * Winter grade fuel with MTBE 6 ------- Table 6. Vehicle UDDS tailpipe emission rates at -20°F. Vehicle Cavalier Taurus Mode No 02 Sensor EGR No 02 Sensor EGR Malfunction Disconnected Disconnected Malfunction Disconnected Disconnected Fuel Base* MTBE* Base MTBE Base MTBE Base MTBE Base MTBE Base MTBE THC, g/mi 1.63 1.5 3.6 3.58 1.74 1.65 1.62 1.53 3.92 2.85 1.67 1.44 CO, g/mi 31.8 25.71 115.95 132.5 32.61 29.14 11.59 13.65 44.69 38.17 10.83 12.26 NOx, g/mi 0.73 0.67 0.85 0.47 0.8 0.54 0.63 0.53 1.05 0.81 0.73 0.64 MTBE, mg/mi <0.01 56.14 <0.01 45.36 <0.01 59.63 NA 73.65 NA 62.82 NA 57.05 Formaldehyde, mg/mi 3.14 2.71 2.85 7 2.41 3.83 2.36 4.16 3.03 1.33 1.97 3.64 Acetaldehyde, mg/mi 2.68 1.1 7.6 6.47 2.66 2.34 2.03 2.63 3.86 1.18 1.77 2.56 Total Aldehydes, mg/mi 7.96 6.3 22.39 21.21 8.7 10.84 8.83 10.24 15.59 4.27 7.09 10.21 Benzene, mg/mi 72.69 35.47 132.14 91.33 82.63 39.76 51.23 39.63 164.8 90.41 61.03 36.94 1,3-Butadiene, mg/mi 5.39 4.52 25.1 9.85 6.58 5.15 8.85 7.99 29.08 16.79 9.87 7.3 PM2.5, mg/mi 25.55 17.3 37.65 22.4 31.9 19.05 60.46 38.06 73.26 33.18 63.15 33.86 PM10, mg/mi 25.05 21.9 36.25 24.8 32.8 21.8 59 37.54 71.86 33.5 63.26 34.58 t t Winter grade fuel without MTBE, Winter grade fuel with MTBE Table 7. Vehicle REP05 tailpipe emission rates. Vehicle Cavalier Taurus Mode No 02 Sensor EGR No 02 Sensor EGR Malfunction Disconnected Disconnected Malfunction Disconnected Disconnected Fuel Base* MTBE* Base MTBE Base MTBE Base MTBE Base MTBE Base MTBE Temperature, THC, g/m 20 F 0.19 0.19 1.36 0.99 0.21 0.15 0.27 0.18 0.68 0.19 0.16 0.15 CO, g/mi 8.38 9.49 70.17 44.04 9.5 8.61 6.48 7.22 16.67 5.71 6.27 5.18 NOx, g/mi 0.59 0.59 0.97 1.35 1.17 0.72 0.57 0.35 1.13 2.06 0.73 0.51 PM2.5, mg/mi 2.0 1.36 2.33 2.0 2.41 1.14 1.9 1.69 2.29 1.35 1.82 1.33 PM10, mg/mi 2.37 1.38 2.61 1.96 2.75 1.31 2.43 1.75 2.26 1.65 2.2 1.46 Temperature, THC, g/m OF 0.32 0.18 1.47 1.22 0.25 0.17 0.28 0.15 0.98 0.29 0.2 0.17 CO, g/mi 13.43 9.09 73.99 69.41 10.82 9.5 8.24 5.41 19.2 8.37 5.98 7.6 NOx, g/mi 0.79 0.74 0.94 0.85 0.99 0.97 0.48 0.41 1.07 1.42 0.63 0.61 PM2.5, mg/mi 1.86 1.68 2.53 1.9 1.82 1.82 3.02 1.22 2.27 1.06 2.44 1.97 PM10, mg/mi 2.23 2.19 2.8 2.36 1.82 2.41 3.22 1.82 3.07 1.36 2.71 2.58 Temperature, THC, g/m -20 F 0.32 0.15 1.51 1.33 0.27 0.15 0.32 0.17 1.28 0.58 0.28 0.15 CO, g/mi 12.28 8.75 76.65 74.07 11.24 10.45 8.51 6.89 23.52 13.93 8.28 5.96 NOx, g/mi 0.71 0.49 0.99 0.8 1.03 1.04 0.5 0.37 1.11 1.1 0.57 0.47 PM2.5, mg/mi 2.0 2.19 3.75 2.98 2.59 2.54 3.68 1.96 4.1 4.77 3.1 2.27 PM10, mg/mi 1.9 2.64 3.66 4.83 3.04 3.08 4.06 1.59 4.57 5.17 3.52 2.95 t i Winter grade fuel without MTBE, Winter grade fuel with MTBE 7 ------- individual hydrocarbons as determined by gas chromatographic analysis. Tables 3-6 summarize the UDDS regulated, toxic, and particulate emission data and Table 7, the REP05 gas phase and particulate data. Emission rates in Table 7 are averages of two tests. Regulated Emissions TotalHydrocarbons-UDDS Cycle — Under normal mode, the Cavalier emitted 6-12 % less hydrocarbons when using the MTBE fuel compared to the base fuel at ambient temperatures in the 20° to -20°F range. The Taurus emissions were 6-26% less under the same test conditions. The hydrocarbon emissions increased with decreasing ambient temperatures for all vehicle-fuel combinations. With the base fuel, the Cavalier emission of 0.49 g/mi at 20°F more than doubled to 1.06 g/mi at 0°F and tripled tol .63 g/mi at -20°F. Corresponding emissions with the MTBE fuel were 0.46 g/mi, 0.62 g/mi, and 1.5 g/mi. The Taurus emission of 0.62 g/mi at 20°F with the base fuel increased to 0.91 g/mi at 0°F and to 1.62 g/mi at -20°F. With MTBE, the Taurus emission of 0.46 g/mi at 20°F almost doubled to 0.81 g/mi at 0°F and more than tripled to 1.53 g/mi at -20°F. Hydrocarbon emissions with the summer grade fuel at 75 °F were 0.19 g/mi and 0.3 g/mi for the Cavalier and the Taurus respectively. The vehicle's engine air/fuel mixture is controlled by a feedback loop via the oxygen sensor. When the sensor is disconnected, the vehicle operates in a slightly rich fuel condition throughout the test cycle. In this malfunction mode, all vehicle-fuel combinations exhibited dramatic increases (86 - 800%) in hydrocarbon emissions compared to the normal mode at all test temperatures. This malfunction mode had a significantly greater impact on the emission of the Cavalier than for the Taurus. The malfunction emissions of the Cavalier which has a smaller engine than the Taurus, were significantly greater for most winter grade fuel-temperature combinations. In only one instance, at -20°F with the base fuel, was the Taurus malfunction emission greater than that of the Cavalier. At 75 °F the Cavalier malfunction mode emission of 1.71 g/mi was nine times those of the normal mode and the Taurus emission of 0.67 g/mi, 2.2 times that of the normal mode. With both winter fuels, the malfunction mode emissions were about 5, 3 and 2 times those of the normal mode at 20°, 0°, and -20 °F respectively for the Cavalier. For the Taurus using the base fuel, the malfunction mode emissions were 3.1,3, and 2.4 times those of the normal mode at 20°, 0° and -20 °F respectively. With the MTBE fuel, the Taurus malfunction emissions were 1.7, 2.2, and 1.9 times those of the normal mode. Malfunction emissions for all vehicle-fuel combinations increased as temperature decreased. The Cavalier malfunction emissions with the base fuel at 20°F increased 25% at 0°F and 48% at -20°F; with the MTBE fuel, the corresponding increases were 27% and 72% respectively. For the Taurus, the corresponding increases were 40% and 103%) respectively with the base fuel, and 76%) and 156% respectively with the MTBE fuel. Disconnecting the EGR resulted in no change in emission of 0.19 g/mi over the normal mode at 75°F for the Cavalier. However, the Taurus emission of 0.24 g/mi was 20% lower than that under normal mode. The malfunction emissions at 20° to -20°F for all vehicle-fuel combinations differ slightly (~ 10%, except the Cavalier with the base fuel at 20°F) from the corresponding normal mode emissions. Malfunction emissions with the base fuel were also slightly higher than with the MTBE fuel. It was surprising to note, however, that at the same test temperature, the Cavalier malfunction emission, in absolute amount, was almost the same as that 8 ------- of the Taurus malfunction emission despite the difference in engine size of the vehicles. It may not be unreasonable to explain this observation as due to the difference in efliciency/size of the catalytic converters of the vehicles. For all vehicle-fuel combinations, the malfunction emissions approximately doubled at 0°F and approximately tripled at -20°F from their initial values at 20°F. Total Hydrocarbons-REP05 Cycle — The REP05 tests in this study were preceded either by a UDDS or another REP05 test. The tests started with an already warm engine and with the catalytic converter performing at or near peak efficiency. REP05 THC emissions for all vehicle-fuel-temperature-mode combinations were therefore expected to be lower than the corresponding UDDS emissions. This has been found to be the case in this study. Under normal mode, the Cavalier THC emissions ranged from 0.19 to 0.32 g/mi with the base fuel and 0.15 to 0.19 g/mi with the MTBE fuel in the temperature range 20° to -20°F. For the Taurus, the emission ranged from 0.27 to 0.32 g/mi with the base and from 0.15 to 0.18 g/mi with the MTBE fuel in the same temperature range. Both the emissions of the Cavalier and the Taurus with the base fuel showed a discernible upward trend with decreasing temperatures. With the MTBE fuel, however, the Cavalier emissions showed a discernable downward trend with decreasing temperatures while with the Taurus, no definitive trend with decreasing temperature was observed. It must be noted that with the MTBE fuel, the emissions at 20°, 0°, and -20°F differed from each other by no more than 0.04 g/mi for the Taurus. For all practical purposes these emissions can be considered almost equivalent. We believe that the predominant factors influencing REP05 hydrocarbon emissions under the normal mode are the temperatures of the engine and the catalyst and not the ambient test temperatures. With the oxygen sensor disconnected, all vehicle-fuel combinations showed dramatic increases in hydrocarbon emissions compared to the normal mode at all test temperatures. With the base fuel, the increases ranged from 359-616% for the Cavalier and 152-300% for the Taurus. With the MTBE fuel, the increases ranged from 421-787% for the Cavalier and 6-241% for the Taurus. As with the UDDS tests, the malfunction emissions of the Cavalier were significantly greater than those of the Taurus at all test temperatures. All vehicle-fuel combinations showed increasing emissions with decreasing test temperatures. From their initial values at 20°F, the Cavalier malfunction emissions at -20°F increased 11% and 34% with the base and MTBE fuels respectively. The corresponding increases for the Taurus were 88% and 205% respectively. Disconnecting the EGR resulted in slight decrease or no change in the malfunction emission relative to the normal mode for all vehicle-fuel combinations, except in case of the Cavalier with the base fuel at 20 °F and of the Taurus with the MTBE fuel at 0°F where the malfunction mode emissions were slightly greater than the normal mode emissions. With the base fuel, the malfunction emissions of the Cavalier increased 29% and those of the Taurus increased 75% when the temperature was changed from 20° to -20°F. With the MTBE fuel, the malfunction emissions of both practically remained the same when the temperature was changed from 20° to -20°F. Carbon M on oxide- UDDS Cycle — The Cavalier normal mode CO emission of 4.51 g/mi at 75 °F was about the same as that of the Taurus. However, from 20 °F to -20 °F, the Cavalier emissions of 10.4-31.8 g/mi with the base fuel were significantly (49-74%) higher than the corresponding emissions from the Taurus; with the MTBE fuel, the Cavalier emissions of 10.6-25.7 g/mi were likewise significantly (74-98%) higher. Emissions from all vehicle-fuel combinations increased with decreasing temperatures. Except at 20°F, emissions from the 9 ------- Cavalier were higher with the base fuel than with MTBE fuel while emissions from the Taurus were higher with the MTBE fuel than with the base fuel. The Cavalier emissions at 20°F increased 207% with the base fuel and 104 % with the MTBE fuel at -20°F. The Taurus emissions at 20°F increased 67% with the base fuel and 124% with the MTBE fuel at -20°F. Disconnecting the oxygen sensor increased dramatically (100-900%) the CO emissions relative to the normal mode emissions for all vehicle-fuel combinations at all test temperatures. At 75°F, the Cavalier emission of 4.51 g/mi increased ninefold and the Taurus emission of 4.58 g/mi more than doubled. Malfunction emissions increased with decreasing temperatures. The Cavalier emission of 94.4 g/mi with the base fuel at 20°F tripled at -20°F; the emission of 77.4 g/mi with the MTBE fuel more than doubled at -20°F. The Taurus emission of 28.4 g/mi with the base fuel increased 57% at -20°F; the emission of 11.4 g/mi with the MTBE fuel more than tripled at -20°F. Except in one instance (Cavalier at -20°F), the malfunction emissions from both vehicles with MTBE fuel were generally lower than the corresponding vehicle emissions with the base fuel. With the base fuel, the Cavalier emissions were about three times those of the Taurus. With the MTBE fuel, the Cavalier emissions were 3.5-6.8 times as much as those of the Taurus. The CO emissions with the winter fuels from both vehicles with entirely malfunctioning EGRs, differed from the normal mode emissions by no more than 23% at all low test temperatures. The Cavalier emissions at this temperature range were 1.6-3 times greater than those of the Taurus. The Cavalier consistently emitted more CO with the base fuel than with the MTBE fuel. The Taurus emissions with the base fuel were slightly greater at 20°F and 0°F than with the MTBE fuel but slightly less at -20°F. The CO emissions of both vehicles increased as the temperature decreased. With the Cavalier, the CO emissions increased by about 160% at -20°F for both the base and the MTBE fuels from their values at 20°F. With the Taurus, the CO emission increases were 42% and 79% for the base and MTBE fuels respectively. Carbon M on oxide-RE P05 Cycle — U nder normal mode, the Cavalier CO emissions (8.3-13.4 g/mi, with base fuel; 8.8-9.5 g/mi, with MTBE fuel) were consistently higher than those of the Taurus (6.0-8.5 g/mi, with base fuel; 6.41-7.2 g/mi, with MTBE fuel) at all test temperatures. Except at 20°F, emissions from both vehicles with the base fuel were greater than those with the MTBE fuel. Emissions from both vehicles with the base fuel showed apparent upward trend with decreasing temperatures while with the MTBE fuel, there were slight indications of downward trends with decreasing temperatures. Disconnecting the oxygen sensor increased the Cavalier emissions with the base fuel from 4.7 to 8.4 times the corresponding normal mode emissions; with the MTBE fuel, 4.6-8.5 times. The Taurus malfunction emissions with the base fuel increased by about 2.5 times the corresponding normal mode emissions; with the MTBE fuel, the emission increase range from -20% to 50% of the normal mode emissions. The Cavalier emissions were consistently higher (100-680%) than those of the Taurus at all temperatures. The CO emissions for all vehicle fuel combinations exhibited increasing trends with decreasing temperatures. Depending on the fuel, the CO emissions of the Cavalier with the EGR disabled ranged from -20% to 20% of the normal mode; with the Taurus, the CO emissions ranged from -28% to 40% of the normal mode. The Cavalier emissions were consistently higher (25-81%) than those of the Taurus at all temperatures. With one exception (Taurus at 0°F), emissions with the base fuel were higher than with the MTBE fuel for all vehicle fuel combinations. The CO emissions for all vehicle fuel combinations exhibited increasing trends with decreasing temperatures. 10 ------- Oxides of Nitrogen - UDDS — Under normal mode at ambient temperature range 20 °F to -20°F, the Cavalier NOx emissions ranged 0.55-0.73 g/mi with the base fuel and 0.64-0.67 g/mi with the MTBE fuel. For the Taurus, the emissions ranged 0.56-0.73 g/mi with the base fuel and 0.45-0.53 g/mi with the MTBE fuel. There were slight indications of upward trends with the Cavalier emissions with both fuels and the Taurus emissions with the MTBE fuel with decreasing temperatures. Emissions of the Taurus with the base fuel, however, showed a slight downward trend with decreasing temperatures. The Cavalier emission at 75°F was 0.69 g/mi; the Taurus, 0.59 g/mi. Disconnecting the oxygen sensor almost doubled (1.16 g/mi) the Cavalier emission and almost tripled (1.69 g/mi) the Taurus emission at 75°F relative to their normal mode values. At the lower test temperatures, both vehicle emissions with the base fuel showed a slight upward trend with increasing temperatures; vehicle emissions with the MTBE fuel showed a downward (especially the Taurus with MTBE fuel) trend. A disabled oxygen sensor had a greater impact on the Taurus NOx emissions than those of the Cavalier. Depending on the temperature, the Taurus NOx emissions were 19-53% greater than those of the Cavalier. Disabling the EGR had a greater impact on the NOx emissions of the Cavalier than those of the Taurus. The impact was more pronounced with the MTBE fuel. At temperature range 0°F to 75°F, the Cavalier NOx emissions increased 40-190% relative to the normal mode emissions. Over this temperature range, the Taurus emissions increased only 25-55% relative to the normal emission values. Depending on the fuel and temperature, the absolute NOx emissions of the Cavalier were 1-1.8 times those of the Taurus. At -20°F, the Cavalier emissions were 10% higher and -16% lower than the Taurus emissions for the base and MTBE fuels respectively. All vehicle-fuel combinations showed decreasing emissions with decreasing winter test temperatures. Oxides ofNitrogen-REPOS — Under normal mode, the Cavalier emitted more NOx (0.49-0.79 g/mi) than the Taurus (0.41-0.58 g/mi) for all vehicle-fuel combinations at all test temperatures. The Cavalier emission with the base fuel showed a slight upward trend with decreasing temperatures while the Taurus showed a downward trend. With the MTBE fuel, the NOx emissions from both vehicles showed a definite downward trend with decreasing temperatures. With one exception (Cavalier at 20°F), NOx emissions with the MTBE fuel were consistently lower than with the base fuel for both vehicles. With a completely disabled oxygen sensor, the Taurus NOx emissions (1.07-2.06 g/mi) were consistently higher than those the Cavalier emissions (0.8-1.35 g/mi) for all vehicle-fuel combinations. With the base fuel, the Taurus NOx emissions increased 98-133% over the normal mode values; the Cavalier, 18-64% over the normal mode values. With the MTBE fuel, the NOx emissions of both vehicles decreased with decreasing test temperatures. With the base fuel, the Cavalier NOx emissions were about the same over the winter test temperature range. Similar variations were observed with the Taurus emissions. The NOx emissions of the Cavalier with a completely disabled EGR increased 22-112% over the normal mode emissions. The Taurus NOx emissions increased 14-45% under the same test conditions. The Cavalier emissions were consistently higher (41-121%) than the Taurus emissions at all test temperatures. The Cavalier and the Taurus emissions with the base fuel showed a downward trend with decreasing temperatures while the Cavalier emissions with the MTBE fuel showed an upward trend with decreasing temperatures. 11 ------- Toxic Emissions Benzene — Besides being present in the fuel itself (see Table 1), benzene is emitted from the tailpipe as a result of its formation during the combustion process involving other fuel components, such as cyclohexane and the alkylaromatics.1011 In one study from 2° to 7% of the benzene was determined to be the result of the rearrangement of these molecules during combustion.12 Benzene emissions showed a general increase as test temperature decreased. A regression plot of HC vs benzene had a R2 of 0.880 and a slope of 32.099 for the Cavalier and a R2 of 0.906 and a slope of 37.37 for the Taurus indicating good correlation with the HC emissions for both vehicles at all test conditions. The correlation of benzene with HC emission as a function of the individual fuel is shown in Figure 1. The MTBE fuel reduced benzene emissions, as compared to the base fuel, for both vehicles and all test modes. Benzene emissions from the Cavalier ranged from a low of 11.07 mg/mi, at 75 °F (EGR disconnected), to a high of 132.14 mg/mi at -20°F (02 sensor disconnected and base fuel), and for the Taurus a low of 7.69 mg/mi, at 75°F (EGR disconnected) to a high of 164.80 mg/mi at -20°F (02 disconnected). 140 - 130 - 120 - 110 - 100 - 90 - 60 - 70 - 60 - 50 - 40 - 30 - 20 - 10 - o - Figure 1. Correlation plots of benzene vs HC as a function of fuel. 1,3-Butadiene — 1,3-Butadiene is not a gasoline component but a by-product of the combustion process. This compound was emitted primarily in the initial 2 minutes (present in the 124 second sample bag) of vehicle start-up, when the air-to-fuel mixture was rich and the vehicle's emission control system was warming up. 1,3-Butadiene emissions from the Taurus increased as test temperature decreased for both fuels and all test modes. A regression plot of HC vs 1,3-butadiene had a R2 of 0.720 and a slope of 5.067 for the Cavalier and a R2 of 0.919 and a slope of 6.742 for the Taurus indicating good correlation with the HC emissions for both vehicles at all test conditions. Emissions from the Cavalier appeared to be test temperature and fuel dependent. The MTBE fuel reduced emissions from the Taurus for all test conditions and in general, also for the Cavalier. The Cavalier emissions ranged from a low of 0.64 mg/mi, at 12 ------- 75°F, to a high of 25.10 mg/mi, at -20°F, and the Taurus emissions ranged from 0.77 mg/mi, at 75 °F, to a high of 29.08 mg/mi at -20°F. Formaldehyde and Acetaldehyde — Formaldehyde and acetaldehyde were not present in the fuel but are by-products of the incomplete combustion of the fuel. These two aldehydes are usually the major aldehydes emitted, with formaldehyde the major emission product. A regression plot of HC vs formaldehyde had a R2 of 0.012 and a slope of 0.174 for the Cavalier and a R2 of 0.081 and a slope of 0.360 for the Taurus indicating no correlation with the HC emissions for either vehicle. Further regressions when temperatures or modes were deleted showed no correlation improvement for either vehicle. The Cavalier formaldehyde emissions ranged from a low of 0.90 mg/mi, at 75°F, to a high of 7.42 mg/mi, at 0°F, and the Taurus formaldehyde emissions ranged from 0.76 mg/mi, at 75 °F, to 4.72 mg/mi at 0°F. A regression plot of HC vs acetaldehyde had a R2 of 0.650 and a slope of 1.835 for the Cavalier and a R2 of 0.679 and a slope of 0.745 for the Taurus indicating fair correlation with the HC emissions for both vehicles at all test conditions. A regression plot of the data without the -20 °F values increased the R2 of the Taurus (0.841) but did not make a significant improvement in the R2 of the Cavalier (0.681). The Cavalier acetaldehyde emissions ranged from a low of 1.10 mg/mi, at -20°F, to a high of 7.60 mg/mi at -20 °F. The aldehyde emissions were greatest when the oxygen sensor was disconnected (vehicle running rich). Particulate Emissions The mass emission rates of the PM2.5 and PM10 particles were about the same for all vehicle-fuel combinations at all test modes and temperatures. Figure 2 shows a very good correlation of the PM10 and PM2.5 particle data. The regression parameters (R2 = 0.995, slope PM2.5, mg/mi Figure 2. Correlation of PM10 and PM2.5 particulate emissions from all vehicle-fuel-mode combinations at all test temperatures. 13 ------- = 0.976, intercept = 0.437) strongly indicate that the particles collected on the cyclone filters were mostly PM2.5 fine particles. PM2.5 and PM10 - UDDS Cycle — The particulate emissions (PM2.5 and PM10) from the UDDS cycle followed the HC and CO trends, and increased as the temperatures decreased. The Taurus, which had a larger engine than the Cavalier, emitted significantly (25-250%) more particles than the Cavalier under normal mode at all test temperatures. Except in one instance (Cavalier at 20°F), both vehicles emitted more particles when using the base fuel than when using the MTBE fuel. The Taurus emitted about twice as much particles with the base fuel than with the MTBE fuel while the Cavalier emitted about 10-35% more with the base fuel than with the MTBE fuel. The Taurus PM2.5 emission of 12.7 mg/mi at 20°F, with the base fuel, quadrupled at -20°F. With the MTBE fuel, the emission (6.2 mg/mi) at 20°F increased sixfold at -20°F. Under the same sets of conditions, the Cavalier PM2.5 emission with the base fuel (3.58 mg/mi) and with the MTBE fuel (3.99 mg/mi) increased 7 and 4.3 times respectively at -20°F. Maximum particulate emission observed for the Taurus was 60 mg/mi with the base fuel and 28 mg/mi with the MTBE fuel, both at -20°F. Corresponding maxima for the Cavalier were 25 mg/mi and 21 mg/mi, respectively. As was noted earlier, disabling the oxygen sensor resulted in dramatic increase of both the HC and CO emissions at all test temperatures compared to the normal mode and that this malfunction mode impacted the emissions of the Cavalier more than those of the Taurus. Particulate emissions did increase with the disconnected oxygen sensor, but the increases were more modest than those of the CO and the hydrocarbons. The Taurus emissions were consistently higher (34-116%) than those of the Cavalier for both fuels at all test temperatures. Over the temperature range 20 to -20°F, the Cavalier particulate malfunction emissions with the base fuel increased on the average by about 54% over the normal mode emissions; with the MTBE fuel, the average increase was about 18%. For the Taurus, the average increase was about 19% with the base fuel and 5% with the MTBE fuel. The malfunction particulate emissions of both vehicles at 20°F increased about 5 times at -20°F. Maximum particulate emissions for the Taurus were 73 mg/mi and 38 mg/mi for the base and MTBE fuel respectively at -20°F. For the Cavalier, maximum particulate emissions were 38 mg/mi and 25 mg/mi for the base and MTBE Figure 3. Correlation plots of PM2.5 vs HC as a function of fuel and oxygen sensor malfunction. 14 ------- fuel respectively at the same temperature. Figure 3 shows the impact of the fuel and the disabled oxygen sensor on PM2.5 emissions. Under the normal mode, the PM2.5 particle generation rates with HC (slope of the regression line) of the Taurus with the base and the MTBE fuels were about twice those of the Cavalier with the same fuel. For the Taurus, the particle generation rate was slightly higher with the base than with the MTBE fuel; for the Cavalier the particle generation rates were about the same for both fuels. However, under the oxygen malfunction mode, the particle generation rates of both vehicles are comparable. With the EGR disconnected, the Cavalier particulate emissions with the base fuel increased on the average by about 43% over the normal mode but hardly no increase (~1%) at all with the MTBE fuel. The Taurus emissions with the base fuel, on the average increased by about 27% over the normal mode; with the MTBE fuel, the increase was about 7%. The Taurus emissions were also consistently higher (53-200%) than the corresponding Cavalier emissions. For both fuels, the Cavalier emissions at 20°F more than quadrupled at -20°F, while the Taurus emissions almost quadrupled with the base fuel and quintupled with the MTBE fuel. Maximum particulate emissions for the Taurus were 63 mg/mi and 35 mg/mi at -20°F with the base and MTBE fuel respectively. Corresponding values for the Cavalier were 32 mg/mi and 22 mg/mi respectively. Figure 4 shows for the same fuel, the EGR malfunction particle generation rates with hydrocarbon emissions are comparable to those under normal mode. Figure 4. Correlation plots of PM2.5 vs HC as a function of fuel and EGR malfunction. PM2.5 and PM10 - REP05 Cycle — The REP05 hydrocarbon emissions were generally low and several factors less than the corresponding values observed with the UDDS cycle. The same low emissions were observed with the PM 2.5 and PM10 particles. Since as indicated earlier, the particles collected on the PM2.5 and the PM10 cyclone filters were mostly PM2.5 particles, it is perhaps more appropriate, especially at these low levels, to present the particulate emission as an average, i.e., (PM2.5 + PM10)/2. Average particulate emissions, in general, increased as the test temperature decreased. Under normal mode, the average particulate emissions with the base fuel were about twice those with the MTBE fuels for both vehicles except for the Cavalier at -20°F. Over the temperature range 20°F to -20°F, the average Cavalier particulate emissions ranged 2.0-2.4 mg/mi and 1.3-2.4 mg/mi with the base and MTBE fuel respectively while those of the Taurus 15 ------- ranged 2.7-3.9 mg/mi and 1.5-1.8 mg/mi for the base and MTBE fuel respectively. The average Cavalier particulate emission at 20 °F with the MTBE fuel about doubled at -20 °F; with the base fuel, the emission decreased by about 10%. The average Taurus particulate emission of 2.16 mg/mi at 20°F with the base fuel doubled at -20°F while emissions with the MTBE fuel remained about the same. Disconnecting the oxygen sensor increased the average particulate emissions of both vehicles. Over the temperature range 20°F to -20°F, the average Cavalier particulate emissions ranged 2.7-3.7 mg/mi with the base fuel and 2.0-2.9 mg/mi with the MTBE fuel. The average Taurus particulate emissions ranged 2.4-4.3 mg/mi with the base fuel and 1.4-4.8 mg/mi with the MTBE fuel. Both vehicle emissions showed upward trends with decreasing temperature. Figure 5 shows regression plots of PM2.5 vs HC emissions of the Cavalier and the Taurus running on base and MTBE fuels under normal and oxygen sensor malfunction mode. No meaningful correlation was observed between the PM2.5 and the HC emissions of the Cavalier with either of the winter grade fuels nor of the Taurus with the MTBE fuel under normal mode. Fair to good correlations were obtained with the Cavalier and the Taurus under malfunction mode and the Taurus with the base fuel under normal mode. The malfunction PM2.5 particle generation rate with HC emissions (slope of the regression line) of the Cavalier was almost three times faster with the base fuel than with the MTBE fuel. With the Taurus, the PM2.5 particle generation rate with HC emissions was in the reverse direction of the fuel; the generation rate was three times faster with the MTBE than with the base fuel. 3,50 ¦ 3.00 1 0,50 ¦ 0.00 • I ~ ~ ~ nD Base Fuel, normal mode, R2=0.000, Slope=0.0 MTBE fuel, normal mode, R2=0.021, Slope=-1.7 Base fuel, 02 sensor disabled, R2=0.622, Slope=7.5 MTBE fuel, 02 sensor disabled, R2=0.592, Slope=2.6 TAURUS REP05 Base Fuel, normal mode, R2=0.801, Slope=20.8 MTBE fuel, normal mode, R2=0.039, Slope=3.1 Base fuel, 02 sensor disabled, R2=0.705, Slope=3.0 MTBE fuel, 02 sensor disabled, R2=0.834, Slope=9.2 0.60 0.80 1,00 1.20 1.40 0,60 0.80 1.00 1.20 Figure 5. Correlation plots of REP05 PM2.5 vs HC as a function of fuel and oxygen sensor malfunction. Average particulate emissions of the Cavalier under the EGR malfunction mode ranged 1.8-2.8 mg/mi with the base fuel and 1.5-2.8 mg/mi with the MTBE fuel. The Taurus malfunction emission ranged 2.0-3.3 mg/mi and 1.4-2.6 mg/mi with the base and the MTBE fuel respectively. The malfunction emissions trended upwards with decreasing test temperatures. The correlation of malfunction PM2.5 particles with HC emissions of the Cavalier was poor (R2 < 0.1) for both fuels. The same was true for the Taurus with the MTBE fuel. Correlation of the normal PM2.5 and the malfunction PM2.5 emissions with HC emissions for the Taurus operating on the base fuel was fairly good (R2 > 0.80). Figure 6 shows regression plots of the normal and 16 ------- CAVALIER REP05 Base Fuel, normal mode, R2=0.000, Slope=0.0 MTBE fuel, normal mode, R2=0.021, Slope=-1.7 Base fuel, EGR disabled, R2=0.074, Slope=6.0 MTBE fuel, EGR disabled, R2=0.012, Slope=14 Base Fuel, normal mode, R2=0.801, Slope=20.8 MTBE fuel, normal mode, R2=0.039, Slope=3.2 Base fuel, EGR disabled, R2=0.849, Slope=10.5 MTBE fuel, EGR disabled, R2=0.009, Slope=4.4 0.10 0,20 0,30 0,00 - 0.40 0,00 TAURUS REP05 Figure 6. Correlation plots of PM2.5 vs HC as a function of fuel and EGR malfunction. malfunction PM2.5 emissions vs HC. The malfunction PM2.5 particulate generation rate as a function of HC emission for the Taurus is about twice as fast as the generation rate under normal mode. SUMMARY AND CONCLUSIONS The regulated (HC, CO, andNOx), the toxic (benzene, 1,3-butadiene, formaldehyde, and acetaldehyde), and the particulate (PM2.5 and PM10) emissions data were obtained from two vehicles operated on three different fuels. These test vehicles could or could not be representative of the on-road fleet. The malfunction conditions introduced are extreme conditions in which the vehicle's oxygen sensor and the EGR valve were rendered completely inoperable. In actuality, the condition of these simulated malfunctions (oxygen sensor and EGR valve disconnected) on-road vehicles could be anywhere in the range of being completely operable and inoperable. Limited resources restricted our testing to two vehicles and to duplicate runs (one at 75°F) at 20°, 0° and -20°F. Also, due to resource limitations we were only able to take only single PM2.5 and PM10 particulate filter from each of the UDDS test cycles (all three phases combined) rather than individual PM2.5 and PM10 particle filter from each of the UDDS's three phases. Hvdrocarbons-UDDS cycle — The MTBE fuel produced less HC emissions than the base fuel for both vehicles. Hydrocarbon emissions increased as test temperature decreased. Maximum THC was emitted when the oxygen sensor was disconnected. Hydrocarbon emissions with the EGR disconnected differed very slightly from the normal mode emissions. The Taurus, which had a bigger engine than the Cavalier, emitted more hydrocarbons at 75 °F than the Cavalier. However, at the winter test temperatures under the normal mode and the EGR malfunction mode, the Taurus emissions were comparable to those of the Cavalier. At the same winter test temperatures when the oxygen sensor was disconnected, the Cavalier emissions were significantly greater than those of the Taurus at all temperatures. We suggest that these 17 ------- significant emission differences can be reasonably attributed to the capacity/efficiency differences of the catalytic converters of the vehicles. Hydrocarbons-REPOS cycle — Hydrocarbon emissions were a few factor lower than the corresponding UDDS emissions. The MTBE fuel produced less emissions than the base fuel for both vehicles. Emissions increased as test temperature decreased. Maximum HC was emitted when the oxygen sensor was disconnected. Under this conditions, the Cavalier emissions were significantly greater than those of the Taurus for both fuels at all test temperatures. The EGR malfunction emissions differ only slightly from the corresponding normal mode emissions. Carbon M on oxide- UDDS cycle — Carbon monoxide emissions with the summer grade fuel were about he same for the Cavalier and the Taurus. At the winter test temperatures, the Cavalier emissions were significantly (49-170%) greater than those of the Taurus under normal mode. The Cavalier emissions with the base fuel were generally greater than those with the MTBE fuel at all test conditions and temperatures. The Taurus emissions with the base fuel were comparable to those with the MTBE fuel under the normal and the EGR malfunction mode. Maximum CO was emitted at each test temperature when the oxygen sensor was disconnected. Under this condition, the Cavalier emissions with the base fuel were about three times higher than those of the Taurus with the base fuel and the Cavalier emission with the MTBE fuel were three to seven times higher than those of the Taurus with the MTBE fuel. Carbon M on oxide-RE P05 cycle — The REP05 CO emissions were decidedly lower than the UDDS emissions under all modes and test temperatures. Emissions were generally higher with the base fuel than with the MTBE fuel for both vehicles. Emissions generally increased as the temperature decreased. EGR malfunction emissions were comparable to the normal mode emissions for each vehicle. Maximum CO was emitted at each test temperature when the oxygen sensor was disconnected. Under this mode, the Cavalier CO emissions with the base fuel were 3-4 times higher than those of the Taurus; with the MTBE fuel, the Cavalier emissions were 5-8 times higher than those of the Taurus with the MTBE fuel. Oxides of Nitrogen - UDDS cycle — With the summer grade fuel at 75 °F, the Cavalier normal mode NOx emission (0.69 mg/mi) increased 68% when the oxygen sensor was disconnected and 190% when the EGR was disconnected. The Taurus normal mode emission (0.59 mg/mi) increased 186%) when the oxygen sensor was disconnected but only 38 % when the EGR was disconnected. With the winter fuels at winter test temperatures, the NOx emissions of both vehicles with the base fuel showed discernable increasing trends with decreasing temperatures under the normal or the oxygen sensor malfunction mode. With MTBE, NOx emissions showed a discernable downward trend. Maximum NOx was emitted at each temperature when the EGR was disconnected for all vehicle-fuel combinations. Emissions trended downward with decreasing temperature under the EGR malfunction mode. Oxides ofNitrogen-REPOS cycle — Normal mode emissions of the Cavalier were about the same at 20° and 0°F for both the base and the MTBE fuel. At -20°F, emission with the base fuel was about 44% higher. NOx emissions of the Cavalier were significantly (4-121%) higher at all temperatures than those of the Taurus under the normal or EGR malfunction mode. However, when the oxygen sensor was disconnected, the Taurus emissions were significantly (12-79%) higher than those of the Cavalier. Except for the Cavalier with the MTBE fuel, NOx emissions trended downward with decreasing temperatures. Benzene — Benzene emissions generally increased as test temperature decreased. Disconnecting the oxygen sensor produced the highest benzene emission rate and the MTBE fuel 18 ------- reduced benzene emissions. Regression analysis shows good correlation between HCs and benzene with both vehicles at all test conditions. 1,3-Butadiene — The 1,3-butadiene emissions increased as test temperature decreased. Disconnecting the oxygen sensor generally produced greater emissions and the MTBE fuel generally reduced emissions. Regression analysis of HCs and 1,3-butadiene indicated fair correlation (R2 = 0.720) for the Cavalier and very good correlation (R2 = 0.919) for the Taurus. Aldehydes — Formaldehyde and acetaldehyde did not show any trends with test temperature, test mode or test fuel. Regression analysis of HCs and formaldehyde showed no correlation (R2 less than 0.1 for both vehicles) but a regression of HCs and acetaldehyde showed a fair correlation (R2 0.650 and 0.679). PM2.5 and PM 10particulate-UDDS cycle — Particulate emissions were mostly PM2.5 particles. Particulate emissions correlated very well (R2 > 0.920) with HC emissions for every vehicle-fuel-malfunction mode combinations. Particle emissions increased 4-5 times when the test temperature was decreased from 20°F to-20°F. Both vehicles emitted more particles with the base fuel than with the MTBE at all test conditions. Taurus particle emissions ranged 13-73 mg/mi with the base fuel and 6-34 mg/mi with the MTBE fuel. The Taurus which had a bigger engine than the Cavalier emitted 2-3 times as much particles as the Cavalier. Maximum particles were emitted when the oxygen sensor was disconnected. Particle emissions with a disconnected EGR differed only slightly from normal mode emissions. PM2.5 and PM If) particulate-REPOS cycle — The REP05 particle emissions (2-5 mg/mi) were several factors lower than the UDDS particle emissions for all vehicle-fuel-malfunction mode combinations. Particle emissions trended upward with decreasing temperatures. The normal mode and the EGR malfunction mode particle emissions of the Cavalier for both the base and the MTBE fuels were about the same. The EGR malfunction mode emissions of the Taurus with the MTBE fuel were slightly higher than those of the normal mode. Maximum particles were emitted when the oxygen sensor was disconnected. ACKNOWLEDGMENTS The authors acknowledge and express gratitude to William Crews and Richard Snow of Clean Air Vehicle Technology Center, Inc. for providing analytical assistance. 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