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Technical Paper

A Correlation Between Tailpipe Hydrocarbon Emissions and Driveability

1996-10-01
962023
Simultaneous tests of emissions and driveability conducted at 4.4°C on a chassis dynamometer using 10 late model vehicles showed a strong correlation between degraded driveability and increased tailpipe hydrocarbon emissions. Other regulated emissions were uncorrelated to driveability, or were small in magnitude. The 24 test gasolines were systematically varied in front-end, mid-range, and tail-end volatility and so spanned much of the moderate and high DI (driveability index) fuel region. Splash blends of 10%.vol ethanol and 15%vol MTBE blended gasolines were tested in addition to hydrocarbon gasolines.
Technical Paper

Gasoline Reformulation and Vehicle Technology Effects on Emissions - Auto/Oil Air Quality Improvement Research Program

1995-10-01
952509
Engine-out and tailpipe exhaust, and hot soak evaporative emissions of two reformulated test gasolines and an Industry Average reference gasoline were compared in four vehicle fleets designed for progressively lower emission standards. The two reformulated gasolines included: 1) a gasoline meeting 1996 California Phase 2 regulatory requirements, and 2) a gasoline blended to the same specifications but without an oxygenated component. These two gasolines were compared with the Auto-Oil Air Quality Improvement Research Program's (AQIRP) Industry Average gasoline representing 1988 national average composition. The vehicle fleets were the AQIRP Older (1983 to 85MY) and Current (1989MY) vehicle fleets used in prior studies, and two new AQIRP test fleets, one designed to 1994 Federal Tier 1 standards and a prototype Advanced Technology fleet designed for lower emission levels of 1995 and later.
Technical Paper

Effects of Gasoline Properties on Emissions of Current and Future Vehicles - T50, T90, and Sulfur Effects - Auto/Oil Air Quality Improvement Research Program

1995-10-01
952510
Exhaust emissions were measured using a matrix of fuels designed to expand on prior AQIRP work by investigating potential interactive effects of fuel distillation parameters T50 and T90, and of T90 and fuel sulfur content. (T50 and T90 represent the temperature at which 50 or 90% of the fuel distills in a standard test.) This fuel matrix was used also to investigate whether fuel effects found in prior work with then-current vehicle technology can be expected to continue in future lower emission vehicles. An additional pair of fuels was included to extend the range of T50. The vehicles were half of the AQIRP Current fleet (ten vehicles) used in prior studies, and two new fleets of six vehicles each. One of the new fleets was designed to 1994 Federal Tier 1 standards, and the other was Advanced Technology prototypes targeted for lower emission levels of 1995 and later. A set of six fuels was tested in all three fleets.
Technical Paper

Emissions with E85 and Gasolines in Flexible/Variable Fuel Vehicles - The Auto/Oil Air Quality Improvement Research Program

1995-10-01
952508
Exhaust and evaporative emissions from three flexible/variable fuel vehicles (FFV/VFV) were measured as the vehicles operated on E85 fuel (a mixture of 85% ethanol and 15% gasoline) or on gasoline. One vehicle was a production vehicle designed for ethanol fuels and sold in 1992-93 and the other two vehicles were prototypes which were recalibrated 1992 model year methanol FFV's. The gasolines tested were Industry Average Fuel A and a reformulated gasoline Fuel C2 that met California 1996 regulatory requirements. The gasoline component of Fuel E85 was based on the reformulated gasoline. The major findings from this three-vehicle program were that E85 reduced NOx 49% compared to Fuel A and 37% compared to Fuel C2, but increased total toxics 108% (5 mg/mi) and 255% (20 mg/mi), respectively, primarily by increasing acetaldehyde. The NOx effect was significant for both engine-out and tailpipe emissions.
Technical Paper

Comparison of CNG and Gasoline Vehicle Exhaust Emissions: Mass and Composition - The Auto/Oil Air Quality Improvement Research Program

1995-10-01
952507
Exhaust emissions of three vehicles fueled with compressed natural gas (CNG) were compared with emissions of three counterpart gasoline vehicles. The natural gas vehicles were tested on four CNG fuels covering a wide range of pipeline natural gas compositions. The gasoline vehicles were tested on AQIRP Industry Average gasoline and a reformulated gasoline meeting California 1996 regulatory requirements. Nonmethane hydrocarbon (NMHC) and toxic air pollutant emissions of the CNG vehicles were about one-tenth those of their counterpart gasoline vehicles, while methane emissions were about ten times those of the gasoline vehicles. Carbon monoxide (CO) and nitrogen oxides (NOx) emissions were more variable among the three vehicle pairs. CO emissions ranged from 20 to 80% lower with CNG than with gasoline, and NOx ranged from 80% lower with CNG to equivalent to gasoline.
Technical Paper

Effects of Gasoline Properties (T50, T90, and Sulfur) on Exhaust Hydrocarbon Emissions of Current and Future Vehicles: Speciation Analysis - The Auto/Oil Air Quality Improvement Research Program

1995-10-01
952505
Species analyses have been performed on engine-out and tailpipe hydrocarbon mass emissions to help understand why fuels with higher T50 and/or T90 distillation temperatures produce higher engine-out and tailpipe hydrocarbon emissions and why fuels with higher T90 distillation temperatures produce higher engine-out and tailpipe specific reactivities. Species analyses were also performed to examine the effects of fuel sulfur level on engine-out and tailpipe species and specific reactivities. These analyses were performed on three different test-vehicle fleets representing varying levels of emissions control technology and the effect of emissions control technology was examined. Individual hydrocarbon species concentrations in both the engine-out and tailpipe were found to correlate linearly with the concentrations of the same species in the fuel, implying that a small fraction of the fuel escapes the combustion process and conversion over the catalyst.
Technical Paper

Effects of Gasoline Properties (T50, T90, and Sulfur) on Exhaust Hydrocarbon Emissions of Current and Future Vehicles: Modal Analysis - The Auto/Oil Air Quality Improvement Research Program

1995-10-01
952504
Modal analyses have been performed on engine-out and tailpipe hydrocarbon mass emissions to help understand why fuels with higher T50 and/or T90 distillation temperatures produce somewhat higher engine-out hydrocarbon emissions and substantially higher tailpipe hydrocarbon emissions. Modal analyses were also performed to examine how increased fuel sulfur increases tailpipe hydrocarbon emissions and to identify which gasoline properties in this study are responsible for the lower tailpipe hydrocarbon emissions with reformulated gasolines. These analyses were performed on three different test vehicle fleets representing varying levels of emissions control technology. The modal analyses showed that the substantially higher tailpipe hydrocarbon emissions from fuels with high T50 and/or T90 distillation temperatures result primarily from these fuels producing substantially higher engine-out hydrocarbon emissions during the first cycle of the Federal Test Procedure (FTP).
Technical Paper

Sources of Vehicles Emissions in Three Day Diurnal SHED Tests - Auto/Oil Air Quality Improvement Research Program

1994-10-01
941965
Three-day diurnal SHED evaporative emissions were measured in a fleet of ten Auto/Oil current (1989) and 2 older (1984) vehicles using Auto/Oil Industry Average fuel. SHED temperature cycled each 24-hour period from 72 to 96 F (22.2 to 35.5C). Measurements included speciation of individual hydrocarbons in the SHED as well as total mass emissions at the end of each of the three 24-hour test periods. Previous evaporative emission studies provided evidence that permeation and/or fuel seepage could contribute significantly to the mass of diurnal and hot soak emissions. Data from this investigation were used to quantify the contribution of liquid fuel to total SHED emissions during diurnal testing. A calculation method, based on the concentration of 29 select hydrocarbons in the SHED, is presented to apportion SHED emissions between those associated with liquid fuel losses and those associated with fuel tank head space vapor losses.
Technical Paper

Emissions with Reformulated Gasoline and Methanol Blends in 1992 and 1993 Model Year Vehicles

1994-10-01
941969
Exhaust and hot soak evaporative emissions were measured in a fleet of 1993 production flexible/variable-fueled vehicles on methanol fuels blended with a reformulated gasoline. A fleet of 1993 California Tier 1 gasoline vehicles was also tested on the same reformulated gasoline blended to meet the specifications of California Phase 2 fuel. Ozone-forming reactivity, expressed as reactivity weighted emissions and specific reactivity, was calculated using 1991 SAPRC and 1994 CBM MIR and MOR factors. Within the FFV/VFV fleet, FTP exhaust and reactivity weighted emissions were significantly lower by 18 to 32% with Phase 2 gasoline relative to Industry Average gasoline. With the exception of greater NMOG emissions with the M85 blends, and lower OMHCE emissions with M85 blended with Industry Average gasoline, exhaust organic emissions, CO and NOx with the methanol fuels were not significantly different than their base gasolines.
Technical Paper

How Heavy Hydrocarbons in the Fuel Affect Exhaust Mass Emissions: Modal Analysis — The Auto/Oil Air Quality Improvement Research Program

1993-10-01
932724
Modal analyses have been performed on engine-out and tailpipe hydrocarbon and carbon monoxide mass emissions to help understand why fuels with increasing amounts of heavy hydrocarbon constituents produce significantly higher tailpipe hydrocarbon emissions, yet do not produce significantly higher tailpipe carbon monoxide emissions. Mass emissions were acquired for a fleet of ten 1989 model year vehicles operating on twenty six fuels of differing heavy hydrocarbon composition. These fuels formed two statistically designed matrices: one examining the effects of medium, heavy, and tail reformate and medium and heavy catalytically cracked components; and the other examining the effects of heavy paraffinic versus heavy aromatic components and the effects of the 50% distillation temperature.
Technical Paper

How Heavy Hydrocarbons in the Fuel Affect Exhaust Mass Emissions: Correlation of Fuel, Engine-Out, and Tailpipe Speciation — The Auto/Oil Air Quality Improvement Research Program

1993-10-01
932725
Species analyses have been performed on engine-out and tailpipe hydrocarbon mass emissions to help understand why fuels with increasing amounts of heavy hydrocarbon constituents produce significantly higher tailpipe hydrocarbon emissions. Mass and speciated hydrocarbon emissions were acquired for a fleet of ten 1989 model year vehicles operating on twenty-six fuels of differing heavy hydrocarbon composition. These fuels formed two statistically designed matrices: one examining the effects of medium, heavy, and tail reformate and medium and heavy catalytically cracked components; and the other examining the effects of heavy paraffinic versus heavy aromatic components and the effects of the 50% distillation temperature. In this paper the fates of fuel species were traced across the engine and across the catalyst, and correlations were developed between engine-out and tailpipe hydrocarbon species emissions and fuel composition.
Technical Paper

Effects of Gasoline Sulfur Level on Exhaust Mass and Speciated Emissions: The Question of Linearity - Auto/Oil Air Quality Improvement Program

1993-10-01
932727
Effects of gasoline sulfur content on emissions were measured in a fleet of ten 1989 model year vehicles. Two ranges of sulfur content were examined. In a set of five fuels, reducing sulfur from 450 to 50 ppm, reduced fleet average tailpipe emissions of HC, NMHC and CO each by about 18%, and reduced NOx 8%. The largest effect on HC and CO emissions was observed in FTP Bag 2. This and the absence of any significant effect on engine emissions indicate that sulfur affected the performance of the catalytic converters. The response of HC and NMHC to fuel sulfur content was non-linear and increased as sulfur level was reduced. In the second set of three fuels, reducing sulfur from 50 to 10 ppm reduced HC and NMHC by 6% and CO by 10%, but had no significant effect on NOx. The effects on HC, NMHC and NOx were not significantly different from predictions based on the prior fuel set. The reduction in CO was larger than predicted.
Technical Paper

Effects of Heavy Hydrocarbons in Gasoline on Exhaust Mass Emissions, Air Toxics, and Calculated Reactivity - Auto/Oil Air Quality Improvement Research Program

1993-10-01
932723
Emission effects of gasoline hydrocarbon components distilling above 300°F were investigated to determine whether the effect of 90% distillation temperature (T90) found in an earlier Auto/Oil Program study is due to fuel distillation properties or to hydrocarbon composition, and also to determine whether the T90 effect is linear. Twenty-six fuels were tested in two sets. In Matrix A, the independent variables were catalytically cracked (FCC) and reformate stocks with nominal distillation ranges of 300 to 350, 350 to 400 and 400+°F. In Matrix B, the independent variables were a reformate stock (320 to 370°F), a heavy alkylate (330 to 475°F), and a light alkylate distilling below 300°F, which was used to vary fuel T50 at fixed levels of T90. Exhaust mass and speciation were measured using ten 1989 vehicles of the Auto/Oil Current Fleet. Tailpipe hydrocarbon emissions were found to increase nonlinearly with progressive addition of the heavier components.
Technical Paper

Fuel Effects in Auto/Oil High Emitting Vehicles

1993-03-01
930137
Fuel effects on exhaust emissions of a sample of seven high emitting vehicles were studied. The vehicles had various mechanical problems and all ran fuel rich. The degree of enrichment varied between tests, and strongly affected mass emissions. Variable enrichment can cause incorrect apparent fuel effects to be calculated if not accounted for in data analysis. After variable enrichment was compensated for, the percentage effects of fuel oxygen, RVP, and olefins were largely in agreement with prior findings for normally emitting vehicles. Reducing fuel sulfur and T90 may have less benefit on hydrocarbon emissions in these high emitters than in normal emitters, and reducing sulfur may have less benefit on CO emissions. Reducing aromatics may be somewhat more helpful in reducing hydrocarbon and CO emissions in the high emitters.
Technical Paper

Fuel Composition Effects on Automotive Fuel Economy - Auto/Oil Air Quality Improvement Research Program

1993-03-01
930138
Fuel economy measurements from portions of Phase I of the Auto/Oil Air Quality Improvement Research Program were analyzed. The following fuel variables were examined: aromatics, olefins, T90, RVP, and various oxygenates (MTBE, ETBE and ethanol). Two vehicle fleets were tested: twenty 1989 vehicles and fourteen 1983-1985 vehicles. Three measures of fuel economy were analyzed. EPA Fuel Economy used the calculation defined in the Federal Register and is an attempt to correct for changes in fuel properties. Volumetric Fuel Economy is based on a carbon balance calculation and is a measure of the actual volume of gasoline burned. Energy Specific Fuel Economy is a measure of fuel economy based on energy content. The following fuel changes resulted in reductions of Volumetric Fuel Economy in both fleets: reduced aromatics, reduced olefins, reduced T90, and addition of oxygenates. Changes in RVP did not have a significant effect on fuel economy.
Technical Paper

Effects of Oxygenated Fuels and RVP on Automotive Emissions - Auto/Oil Air Quality Improvement Program

1992-02-01
920326
Exhaust and evaporative emissions were measured as a function of gasoline composition and fuel vapor pressure in a fleet of 20 1989 vehicles. Eleven fuels were evaluated; four hydrocarbon only, four splash blended ethanol fuels (10 vol %), two methyl tertiary-butyl ether (MTBE) blends (15 vol %) and one ethyl tertiary-butyl ether (ETBE) blend (17 vol %). Reid vapor pressures were between 7.8 and 9.6 psi. Exhaust emission results indicated that a reduction in fuel Reid vapor pressure of one psi reduced exhaust HC and CO. Adding oxygenates reduced exhaust HC and CO but increased NOx. Results of evaporative emissions tests on nineteen vehicles indicated a reduction in diurnal emissions with reduced Reid vapor pressure in the non-oxygenated and ethanol blended fuels. However, no reduction in diurnal emissions with the MTBE fuel due to Reid vapor pressure reduction was observed. Reducing Reid vapor pressure had no statistically significant effect on hot soak emissions.
Technical Paper

The Effects of Methanol/Gasoline Blends on Automobile Emissions

1992-02-01
920327
This report presents the Auto/Oil AQIRP results of a methanol fueled vehicle emission study. Nineteen early prototype flexible/variable fueled vehicles (FFV/VFV) were emission tested with industry average gasoline (M0), an 85% methanol-gasoline blend (M85), and a splash-blend of M85 with M0 (gasoline) giving 10% methanol (M10). Vehicle emissions were analyzed for the FTP exhaust emissions, SHED diurnal and hot soak evaporative emissions, and running loss evaporative emissions. Measurements were made for HC, CO and NOx emissions and up to 151 organic emission species, including air toxic components. M0 and M10 emissions were very similar except for elevated M10 evaporative emissions resulting from the high M10 fuel vapor pressure. M85 showed lower exhaust emissions than M0 for NMHC (non-methane hydrocarbon), OMHCE (organic material hydrocarbon equivalent), CO and most species. M85 had higher exhaust emissions for NMOG (non-methane organic gases), NOx, methanol and formaldehyde.
Technical Paper

The Effect of Aromatics, MTBE, Olefins and T90 on Mass Exhaust Emissions from Current and Older Vehicles - The Auto/Oil Air Quality Improvement Research Program

1991-10-01
912322
Exhaust emissions were measured as a function of gasoline composition in two fleets of vehicles - 20 1989 vehicles and 14 1983-1985 vehicles. Eighteen different gasolines were tested which varied in aromatic, olefin, and MTBE content and in the 90 percent distillation temperature (T90). Subject to the cautions and qualifications described in the body of this paper, mass exhaust emissions in both fleets of vehicles were affected by changes in fuel composition. Responses to changes in MTBE and olefins were similar in both fleets: adding MTBE reduced emissions of HC and CO, and reducing olefins lowered emissions of NOx while raising emissions of HC. In the current fleet, reducing aromatics lowered HC and CO, while in the older fleet, reducing aromatics raised HC and lowered NOx. In the current fleet, lowering T90 reduced HC over 20%, while raising NOx slightly. In the older fleet, lowering T90 reduced HC by only 6%.
Technical Paper

Effects of Gasoline Sulfur Level on Mass Exhaust Emissions - Auto/Oil Air Quality Improvement Research Program

1991-10-01
912323
In this portion of the Auto/Oil Air Quality Improvement Research Program, ten 1989 model vehicles were tested using two fuels with different sulfur levels. These tests were run to determine instantaneous effects on exhaust emissions, not long-term durability effects. The high- and low-sulfur fuels contained 466 ppm and 49 ppm sulfur, respectively. Mass exhaust emissions of the fleet decreased as fuel sulfur level was reduced. Overall, HC, CO, and NOx were reduced by 16, 13, and 9 percent, respectively, when fuel sulfur level decreased. This effect appeared to be immediately reversible. Engine-out mass emissions were unaffected by changes in the fuel sulfur content, therefore, tailpipe emissions reductions were attributed to increased catalyst activity as the sulfur level was reduced.
Technical Paper

Description of Auto/Oil Air Quality Improvement Research Program

1991-10-01
912320
An overview of Phase 1 of the Auto/Oil Air Quality Improvement Research Program is presented. Specific information is provided on each of the individual test fuel matrices that were conducted to investigate vehiclelfuel “system” effects on emissions. Procedures for sampling exhaust, evaporative, and running loss vehicle emissions are described, as well as techniques developed for speciation of individual hydrocarbons. Air quality models to project ozone reduction potential of reformulated gasolines and methanol, and economic studies to estimate the relative cost-effectiveness of the vehiclelfuel alternatives are also briefly explained.
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