United States Environmental Protection Agency Atmospheric Sciences Research Laboratory Research Triangle Park NC 27711 Research and Development EPA-600/S3-84-104 Dec. 1984 Project Summary Characterization of Heavy-Duty Motor Vehicle Emissions Under Transient Driving Conditions Mary Ann Warner-Selph and Harry E. Dietzmann The objective of this program was to characterize heavy-duty diesel truck and bus emissions produced during transient driving cycles. In the initial phase of the program an improved road- load simulation method was developed for use in operating large trucks on a chassis dynamometer. This method was used in testing vehicles on the chassis dynamometer in the latter parts of the program. The second phase of testing involved operation of six vehicles on the chassis dynamometer (over the chassis version of the heavy-duty trans- ient cycle), removal of the engine and testing of the engines (over the heavy- duty engine transient cycle). Chassis emisisons were then compared to en- gine emissions. Additionally, chassis tests were conducted over a range of dynamometer inertia settings for two of the six vehicles for the purpose of comparison with engine emissions. Baseline emissions were also measured on six buses, five single-axle tractors, and 17 dual-axle tractors over the chassis version of the transient cycle. Regulated emissions and several unregulated emis- sions were measured on baseline tests. Unregulated emissions included partic- ulate, aldehydes and ketones, phenols, DOAS odor, various elements, nitro- pyrenes, and Ames mutagenic re- sponse. This Project Summary was developed by EPA's Atmospheric Sciences Re- search Laboratory, Research Triangle Park, NC, to announce key findings of the research project that is fully docu- mented in a separate report of the same title (see Project Report ordering information at back). Introduction This project was divided into three tasks. The objective of the first task of testing was to determine the appropriate amount of power to be absorbed by a chassis dynamometer to simulate on- road driving conditions. The work per- formed in the first task involved three vehicles, a city bus, a single-axle truck tractor, and a tandem-axle truck tractor. Coastdowns were conducted on the road for each vehicle under essentially ideal weather conditions (primarily no wind) and with zero road grade. Coastdowns were also conducted on the chassis dynamometer with the single-axle tractor and the bus. Results of these determina- tions, along with data reported in the literature, were used to determine the power to be absorbed by a chassis dynamometer. The objectives of the second task were to determine repeatability of HC, CO, COZ, NO,, and particulate emissions in chassis cycle and engine cycle tests and whether there is correlation between engine cycle and chassis cycle emissions. This task involved five sets of tests with four vehicles over a chassis version of the transient cycle for heavy-duty vehicles and with their respective engines over the 1984 transient test for heavy-duty engines. The test vehicles included a city bus powered by a 1 982 Detroit Diesel 6V-71, two dual-axle tractors, one with a 1980 Cummins Formula 350 and one with a 1980 Detroit Diesel 8V-92TA, and a single-axle tractor equipped with a 1979 IHC DT-466. Two additional vehicles underwent two sets of chassis and engine ------- tests. These vehicles were also tested at several different inertia settings over the chassis transient cycle to determine the effect of inertia on emissions. Regulated emissions (HC, CO, C02, and NOX) and participate were measured for all chassis and engine transient tests. The city bus was tested using a DF-1 Emissions Test Fuel (EM-400-F) and the three tractors were tested with a DF-2 Certification Fuel (EM-528-F). The objective of the third task was to measure HC, CO, C02, NOX, paniculate and several unregulated emissions during chassis testing of four single-axle trac- tors, fifteen dual-axle tractors, and five buses. Each vehicle was operated over a minimum of two duplicate transient cy- cles. The buses were tested with a DF-1 Emissions Test Fuel (EM-455-F), and the tractors were tested with a DF-2 Certi- fication Fuel(EM-528-F).The unregulated emissions that were measured included aldehydes and ketones, DOAS odor, various elements, and organic solubles. In addition, Ames bioassay and nitro- pyrene analyses were performed on the organic soluble samples. Procedures Dynamometers and CVS Systems Transient engine testing was performed in accord with the 1984 Transient test for Heavy-Duty Diesel Engines. The proce- dure specifies transient engine operation over variable speed and load, the magni- tude of the load depending on the power output capability of the test engine. The cycle requires relatively rapid dynamom- eter control, that is, the capability to load the engine one moment and motor it the next. The system used in this program consisted of a GE 200 hp motoring/250 hp absorbing dynamometer coupled to a Midwest 500 hp eddy current (absorbing) dynamometer, with a suitable control system fabricated in-house. Engine transient testing of Engine 2-1 was conducted using a double-dilution constant volume sampler (CVS) with the main dilution tunnel flow set at 1100 CFM. Engines 2-2, 2-3, and 2-4 were operated with a main dilution flow of 1900 CFM. This provided a dilution ratio of roughly 4:1 in the primary tunnel and 12:1 in the secondary tunnel. Secondary tunnel sample flowrates were about 1 CFM for all engine transient tests. Chassis transient operation was con- ducted in general accord with the EPA Recommended Practice for determining exhaust emissions via the chassis version of the Transient Cycle. Vehicle testing was performed on a tandem drive dyna- mometer equipped with two air-gap 350 hp eddy current power absorbers and with inertia wheels directly connected to each set of rolls. A speed vs load curve, simulating road-load horsepower, was programmed into the system using a load control circuit. A single dilution CVS with maximum capacity of 12,000 cfm was used with vehicles tested on the chassis dynamom- eter. The CVS was set at flow rates ranging from 4000 to 9000 cfm, depend- ing on engine horsepower and ambient temperature. Driving Cycles Vehicle testing involved vehicle opera- tion over three different driving cycles: the 1984 Transient FTP for Heavy-Duty Diesel Engines, the "Recommended Prac- tice for Determining Exhaust Emissions from Heavy-Duty Vehicles Under Trans- ient Conditions," and the New York Bus Cycle. The 1984 engine transient cycle is described in the Federal Register by percent of maximum torque and percent of rated speed for each one-second interval, for a test cycle of 1199 seconds duration. This 20-minute transient cycle is composed of four five-minute seg- ments. The four segments are described as follows: Engine Transient Cycle Segment Time, sec New York Non-Freeway 297 (NYNF) Los Angeles Non-Freeway 300 (LANF) Los Angeles Freeway (LAP) 305 New York Non-Freeway 297 (NYNF) The chassis transient test is composed of a cold-start cycle followed by a 20- minute soak period and then a hot-start cycle. On the day preceding testing the vehicle is propped by driving through the chassis transient test. The vehicle is then allowed to stand overnight prior to the cold-start. The transient cycle is com- posed of four segments which are des- cribed as follows: Chassis Transient Cycle Segment Time, sec New York Non-Freeway (NYNF) 254 Los Angeles Non-Freeway 267 (LANF) Los Angeles Freeway (LAP) 285 New York Non-Freeway 254 (NYNF) One chassis transient cycle is a total of 1060 seconds, or approximately 18 min- utes. Although engine and chassis trans- ient cycles are quite similar in most respects, differences in cycle lengths exist because of inherent differences in the chassis and engine test procedures. Another driving cycle used in testing of buses in Task 3 was the New York Bus Cycle. This experimental driving cycle was developed from a CAPE-21 study of several buses during in-service operation. Of the 1191 seconds duration of the cycle, 394 seconds are idle. The distance covered by the test is 2.90 miles and the maximum speed called for by the cycle is 36 mph. Unregulated Emissions Phenols Phenols were sampled by bubbling dilute exhaust at 0.8 ftVmin through glass impingers containing a chilled aqueous solution of 1 N potassium hydrox- ide. The samples were acidified, extracted with ether, and concentrated. Samples were analyzed on a gas chromatograph equipped with a flame ionization detector. This procedure analyzes for phenol, sali- cylaldehyde, m-cresol/p-cresol, p-ethyl- phenol/2-isopropylphenol/2,3-xylenol/ 3,5-xylenol/2,4,6-trimethylphenol, 2,3,5- trimethylphenol, and 2,3,5,6-tetramethyl- phenol. Aldehydes and Ketones Two variations of the 2,4-dinitrophenyl- hydrazme (DNPH) method were used in the analysis of aldehydes and ketones. The first method involved sampling dilute exhaust at 4 lit/min through an aqueous 2N HCI scrubber solution of DNPH. The samples were filtered, extracted with pentane, and analyzed on an HPLC. The compounds measured were formalde- hyde, acetaldehyde, acrolein, propional- dehyde, acetone, crotonaldehyde, isobu- tyraldehyde, methylethylketone, benzal- dehyde, and hexanaldehyde. This pro- cedure was used for Vehicles 3-1 through 3-7. An improved version of the 2,4-DNPH method was used to analyze samples from Vehicles 3-8 to 3-24. Dilute exhaust was bubbled through a solution of DNPH in acetonitrile spiked with 1N perchloric ------- acid. A portion of the sample was analyzed by direct injection into an HPLC. The same aldehydes and ketones were meas- ured with this method as with the original procedure, however, isobutyraldehyde and methylethylketone elute at the same retention time. DOAS Odor Dilute exhaust was sampled at approx- imately 2.8 lit/min for odorants using stainless steel traps packed with Chromo- sorb 102. Two traps were positioned in series for each sample taken. Samples were eluted from the traps with cyclo- hexane and a portion of each sample was analyzed on the Diesel Odor Analysis System (DOAS), a liquid chromatograph. Elements Paniculate samples were collected on 47 mm Pallflex filters. The particulate from these filters was analyzed for several elements at EPA-RTP using a Siemens Model MRS-3 high resolutionx-rayfluor- escence multispectrometer. Solvent Extraction of Particulate Filters Particulate was also sampled on 20x20 inch Pallflex filters. These filters were Soxhlet extracted with methylene chlor- ide for 8 hours at 4 cycles/hour and the resulting extractables were analyzed for nitropyrenes and for mutagenic activity (Ames Bioassay). Nitropyrenes Nitropyrenes were measured using a method developed by the EPA in which the samples were analyzed on a liquid chromatograph coupled to a fluorescence detector. Each organic extractable sample was dissolved in a 50:50 mixture of methylene chloride/methanol prior to analysis. The liquid chromatograph is equipped with four columns, two contain- ing reduction catalyst, and two packed with Zorbax ODS. The catalyst columns remove oxidative compounds from the solvent and convert nitropyrenes to the highly fluorescent aminopyrenes. The Zorbax ODS columns separate the com- pounds in the sample. This procedure analyzes for 1-nitropyrene and three dinitropyrenes: 1,3-, 1,6-, and 1,8-dinitro- pyrene. Ames Bioassay Organic extractables were analyzed for mutagenic activity by the S. typhimurium mutagenicity test (Ames test), in tester strains TA1538, TA98, and TA100. The samples were analyzed in triplicate for mutagenic activity in the presence and absence of the S9 external metabolic activation system, Aroclor-induced rat liver homogenate. Results The first task of vehicle testing involved operation of six vehicles over the chassis transient cycle, removal of the respective engines, and subsequent engine opera- tion over the engine transient cycle. The emissions results from these tests are summarized in Tables 1 and 2 in g/km and g/kg fuel. Engine emissions in g/km were calculated based on an engine cycle equivalent distance of 10.3 km. This value was determined by the EPA in 1978. Hydrocarbons (HC), carbon mon- oxide (CO), oxides of nitrogen (NO,), and particulate were measured and are re- ported as composite values weighted 1 /7 cold-start and 6/7 hot-start. Vehicle 3-23 was inadvertently tested at 80 percent of standard horsepower. All other vehicles were tested at standard horsepower. HC chassis emissions, in g/km, generally exceeded engine emissions by 10 to 30 percent with the exception of Vehicle 2-1, in which chassis HC was lower than engine HC by 16 percent. Vehicle 3-23 emitted the highest level of chassis and engine HC while Vehicle 2-4 produced the lowest levels. Vehicle 2-1 had rela- tively high chassis CO emissions, 21 g/km compared to the other vehicles, 2 to 6 g/km. NOX emissions from Vehicles 2- 2, 2-3, 2-4, and 3-24 chassis and engine tests agreed within 11 percent. However, NOX produced by Vehicle 2-1 during chassis tests exceeded engine NOX by 65 percent while NOX from vehicle 3-23 chassis tests were 38 percent lower than engine NO*. Vehicle 3-24 produced the highest NOX levels of the six vehicles. Particulate emissions from chassis tests were generally higher th-n particulate produced during engine testing (by 18 to 28 percent). Vehicle 2-3 produced nearly equivalent amounts of particulate in chassis and engine tests. Particulate emissions from chassis tests of Vehicle 2-1 were double the amount of particulate emissions from engine tests. Engine and chassis emissions are also reported on a fuel specific basis, in g/kg fuel. The general trends observed be- tween engine and chassis emissions in g/km are similar. However, in about half the measurements, the agreement between engine and chassis emissions improved when using fuel specific units for reporting emissions. Two of the six vehicles that were tested over chassis and engine cycles were also tested at several inertia weights over the chassis transient cycle. Chassis transient Table 1. Comparison of Emissions from Chassis and Engine Tests from Several Vehicles Composite Emission Rate, g/km Vehicle Number Vehicle Description HC CO NO, Part. Chassis Engine" Chassis Engine' Chassis Engine" Chassis Engine' 2-1 BusDD6V-71 2-2 Dual-Axle Cummins Form. 350 2-3 Dual-Axle DD8V-92TA 2-4 Single-Axle IHC DT-466 3-23 Single-Axle Cummins NTC-300 3-24 Dual-Axle DD8V-92TA 1.74 2.06 1.72 1.15 3.16 1.62 2.08 1.88 1.34 1.00 2.80 1.36 21.4 5.56 2.24 2.82 3.70 4.67 5.92 4.39 4.33 2.62 5.55 6.66 108 14.3 13.4 891 8.99 17.6 6.56 13.7 15.1 8.31 14.6 187 1.28 0.97 0.87 0.78 1 19 1.35 0.63 0.82 0.89 0.64 093 1.14 "Engine transient emission rate based on an engine equivalent distance of 10.3 km. ------- Table 2. Comparison of Fuel Specific Emissions from Chassis and Engine Transient Tests from Several Vehicles (g/kg fuel) Composite Emission Rate, g/kg fuel Vehicle Number 2-1 2-2 2-3 2-4 3-23 3-24 HC Chassis 4.23 4.69 3.81 3.69 9.60 3.18 Engine 7.25 4.83 2.97 3.63 7.26 2.71 CO Chassis 51.9 12.7 4.97 8.89 11.2 9.17 Engine 20.5 11.3 9.50 9.47 14.4 13.3 NO, Chassis 26.4 32.7 29.8 281 27.2 34.4 Engine 22.8 34.6 33.2 30.1 37.9 372 Paniculate Chassis 3.10 2.21 1.93 2.50 3.59 2.64 Engine 2.21 2.12 1.94 2.30 2.42 2.28 testing is usually conducted at 70 percent of GVW. Vehicle 3-23, a single-axle tractor, was tested at 61%, 70%, 80%, and 93% of GVW. Vehicle 3-24, a dual- axle tractor, was operated at 55%, 70%, 86%, and 97% of GVW. Emissions results from these tests and from engine tests are reported in Tables 3 and 4 in g/km and in g/kg fuel, respectively. Vehicle 3- 23 C02 and NOX increased with increasing inertia when measured in g/km. On a fuel specific basis, however, C02 was constant while NO* increased with in- ertia. HC and particulate were not affected by variations in inertia. For the dual-axle tractor. Vehicle 3-24, CO, C02, and NOX emissions (in g/km) increased as inertia weight was added. On a fuel specific basis, C02 remained constant and CO and NOX increased. Similar to Vehicle 3-23, HC and particulate did not vary with inertia weight with the exception of fuel specific HC, which decreased with in- creased inertia. There was no single inertia setting at which chassis emissions were equivalent to engine emissions. For some emissions, chassis and engine emissions were never equivalent. This occurred with Vehicle 3- 23. Chassis particulate emissions were higher and CO, COj, and NOX emissions were lower than engine emissions. For Vehicle 3-24, chassis HC wfls greater than engine HC and chassis CO and NOX (in g/kg fuel) were lower than engine emissions at all inertia settings. Baseline emissions were measured on six buses, five single-axle tractors, and 17 dual-axle tractors over a minimum of two chassis transient cycles. Five of the six buses were also tested over two cycles of the New York Bus Cycle. Average baseline emissions (in g/km and g/kg fuel) are given in Table 5 for each vehicle type and for buses tested over the Bus Cycle. As a group, single-axle tractors produced rel- atively high HC levels and relatively low NO. and particulate. Dual-axle tractors emitted relatively high C02 and NOX and low HC and CO. Buses tested over the Table 3. Comparison of Engine and Chassis Emissions from Vehicles 3-23 and 3-24 Measured at Several Inertia Settings (g/km) Vehicle Number 3-23" 3-24 Vehicle Description Single-axle 1981 Cummins NTC-300 Dual-axle 1980 DD8V-92TA Engine Emissions, g/km" Percent HC CO COi NO," Part. of GVW 2.80 5.55 1211 14.6 0.93 61% 70% 80% 93% 1.36 6.66 1583 18.7 1.14 55% 70% 86% 97% Chassis Emissions, g/km HC 3.33 3.16 3.54 3 14 1 71 1.62 1.65 1.66 CO 3.79 3.70 4.15 4.20 3.36 4.67 5.81 7.62 C02 1006 1036 1110 1152 1416 1609 1775 1847 /V0xb 8.37 8.99 10.4 10.8 14.4 17.6 19.8 21.5 Part. 1.22 1.19 1.31 1.26 1.14 1.35 1.26 1 41 * Engine emission rates are based on a 10.3 km engine test cycle. "NO, from bag measurement. "Vehicle 3-23 chassis emissions were measured at 80 percent of standard horsepower. Table 4. Comparison of Composite Fuel Specific Engine and Chassis Emissions from Vehicles 3-23 and 3-24 Measured at Several Inertia Settings (g/kg fuel) Vehicle Number 3-23" 3-24 Vehicle Description Single-axle 1981 Cummins NTC-300 Dual-axle 1980 DD8V-92TA Engine Emissions, g/kg fuel Percent HC CO C02 NO," Part. of GVW 7.26 14.4 3136 379 2.42 61% 70% 80% 93% 2.71 13.3 3153 37.2 2.28 55% 70% 86% 97% Chassis Emissions, HC 10.4 9.60 10.0 8.55 3.83 3.18 2.93 2.82 CO 11.8 11.2 11.7 11.4 7.50 9.17 10.4 13.0 C02 3128 3130 3128 3134 3156 3155 3154 3150 g/kg fuel NO," 26. 1 27.2 30.0 29.6 32.1 34.4 35.2 36.7 Part. 3.80 3.59 3.68 3.44 2.53 2.64 2.24 2.41 "NO, from bag measurement. ^Vehicle 3-23 chassis emissions were measured at 80 percent of standard horsepower. ------- chassis transient cycle produced relative- ly high CO and particulate and low HC compared to single- and dual-axle trac- tors. Bus CO emissions were 4 to 6 times higher than tractor CO emissions and bus particulate was double that of tractor particulate emissions. Bus emissions from the New York Bus Cycle generally exceeded chassis trans- ient cycle emissions with the exception of fuel specific C02 and NO,. The greatest difference between driving cycles was for Table 5. Summary of Baseline Emissions from Single-Axle Tractors, Dual-Axle Tractors, and Buses Over the Chassis Version of the Transient Cycle and of Buses Over the New York Bus Cycle Emission Rate, g/km Emission Rate, g/kg fuel HC CO COi NO, Part. HC . CO CO2 NO, Part. Single-Axle Tractors Average Std. Dev. Coef. of Var. (%) 1.94 0.86 44 3 1 .75 .26 34 1056 70 7 9.37 0.81 9 1.07 0.28 26 5.75 2.50 44 11.1 3.5 32 3144 12 <0.5 28.1 3.6 13 3.19 0.73 23 Dual-Axle Tractors Average Std. Dev. Coef. of Var. (%) Average Std. Dev, Coef. of Var. (%) Average Std. Dev. Coef. of Var. (%) 1.74 7.19 0.48 4.58 28 64 1.71 27.4 0.10 16.6 6 61 2.23 48.0 0.32 28.6 14 60 1464 106 7 17.0 2.9 17 1.47 0.55 37 3.74 1.04 28 15.3 9.2 60 3142 16 1 35.5 5.4 15 3.15 1.10 35 Buses 1233 12.4 37 3.0 3 24 2.46 4.23 67.4 3045 30.7 6.04 1.45 030 40.7 64 7.4 3.56 59 7 60 2 24 59 Buses Over New York Bus Cycle 1488 15.2 3.89 4.51 95.9 3000 30.7 7.74 32 3.1 2.30 0.76 55.5 86 7.0 4.40 2 20 69 17 58 3 23 57 Table 6. Summary of Unregulated Emissions from Single-Axle Tractors, Dual-Axle Tractors, and Buses Over the Chassis Transient Cycle Emission Total Aldehydes and Ketones, mg/km° Phenols, mg/km0 DOAS odor LCA, mg/km LCO, mg/km Phosphorus, mg/kma Sulfur, mg/kma 1 -nitropyrene, ug/km* Ames bioassay, revertants/km TA1538+S9 -S9 TA98 +S9 -S9 TA100 +S9 -S9 Single-Axle Tractors 451 NDC 253 130 1 19 5 440 208 438 359 414 560 Dual-Axle Tractors 238 ND 340 204 2 28 8 277 262 304 345 343 434 Buses 381 ND 895 101 3 9 ND 127 47 128 63 285 196 fAverage included only those vehicles analyzed with improvedDNPH method. "Negligible phenol levels measured. CND = Not Detected. ''Most common elements detected were phosphorus and sulfur. "No dinitropyrenes detected above 1fjg/km. CO and particulate emissions. Unregulated emissions were measured for 24 of the baseline test vehicles. Aldehydes and ketones, phenols, and odor were sampled over one cold-start and three hot-starts. Elemental composi- tion and soluble organic fractions (for nitropyrene and Ames bioassay) were determined on filters sampled during one cold-start and filters sampled over one hot-start. Unregulated emissions results are summarized in Table 6. The emissions represent composite values weighted 1 /I cold-start and 6/7 hot-start. As a group, single-axle tractors pro- duced higher than average total alde- hydes and ketones and relatively high Ames response. They also emitted lower than average LCA odor and phosphorus relative to all vehicle types. Dual-axle tractors produced relatively high LCO odor, sulfur, and 1 -nitropyrene levels and low levels of aldehydes and ketones. Buses tended to produce higher than average LCA odor and phosphorus and relatively low amounts of 1-nitropyrene and low Ames response. Recommendations Results reported in this study have provided an important step forward in understanding the relationship between engine and chassis testing, as well as providing a significant data base for the characterization of heavy-duty trucks and buses for gaseous, particulate and un- regulated emissions. Upon completion of this program, it was apparent many areas of investigation remain, before the know- ledge of heavy-duty truck and bus emis- sions approach that of the automobile. Several of the areas suggested for addi- tional research are briefly described by various vehicle categories. City Buses Engine versus chassis comparisons of a city bus showed virtually no agreement of gaseous or particulate emissions. Additional work is recommended to in- clude engine versus chassis comparisons on a different bus with the same engine model. This study should include the engine bus transient cycle (a cycle not available at the time of this study) as well as several inertia weights during chassis testing. Additional buses should be included that would expand the data base to include the DD 6V-92TA and Cummins V-903 engines, and other engines repre- senting significant fractions of the bus population. These evaluations should ------- include both chassis and engine testing for these engines. Consideration should be also given to developing a different bus cycle, if it is felt that the current cycle is not representative of real life bus opera- tion. Dual-Axle Diesel Truck Tractors This program generated a substantial amount of emissions characterization from a variety of dual-axle tractors. These vehicles basically represent engine pro- duction from 1979-1981. Although most of the major engine models were included in this study, there will undoubtedly be new models introduced each year. In order to keep current on in-use emissions characterization of heavy-duty vehicles, it is suggested that EPA continue a limited amount of characterization to include new technology engines that will be built to meet the particulate standards. Several factors influence the gaseous and particulate emissions from a given engine in a dual-axle truck. The influence of inertia weight on emissions was in- vestigated in this study, but this was only a first step in understanding the relation- ship between chassis and engine emis- sion results. For example, how much does the transmission and gear-train affect emissions, do the tires influence emissions results, do assumptions in frontal area significantly affect emissions from dual-axle tractor. Many of the ques- tions could be answered by obtaining two vehicles with identical engines, but dif- ferent drive trains, tires, etc.; testing the vehicles over the chassis cycle; then removing the engine and testing them over the engine transient cycle. Upon completion, the engines would be switched from their original chassis and the chassis testing repeated. This would provide information to determine if as- sumptions made during chassis testing significantly affect emissions as well as expand the data base for engine chassis comparisons. In addition, hot-start eval- uations would be conducted at several horsepower settings and inertia weights to further assess the effects of these parameters. Single-Axle Diesel Truck Tractors Results of two engine-chassis compar- isons were obtained in this study. In one case (IHC DT-466B), good agreement was observed, but in the other case {Cummins NTC-300), virtually no agree- ment between chassis and engine emis- sions was observed. In the case where good agreement was observed, the engine power to vehicle weight appeared to be more "normally" matched for a single- axle truck tractor. In the case of the second engine with virtually no agree- ment in emission results, the Cummins NTC-300 engine had a relatively high power to vehicle weight ratio. Several of the single-axle tractors had engines with relatively high power to vehicle weight ratios. The Cummins NTC-300 engine in a dual-axle tractor would probably provide a better agreement of chassis and engine emission results. If it is felt that a significant fraction of the single-axle, truck tractor population is in this category, then additional work would be warranted. This work could be similar to that des- cribed earlier, with a given engine model (e.g., Cummins NTC-300) being used in both single- and dual-axle tractors for chassis testing. This engine would also be tested over the engine transient cycle. The chassis tests should include various horsepower settings to simulate different frontal areas and different inertia weights to simulate different loadings. Additional emissions characterization is also in order for single-axle tractors to include engines that were not available for this study and possibly include Class VI diesel vehicles. As the technology for developing low particulate heavy-duty diesel engines becomes available, it is suggested that EPA continue the char- acterization study at a low-level of effort. Heavy-Duty Gasoline Vehicles In-house studies in progress at EPA in Research Triangle Park are addressing heavy-duty gasoline vehicles requiring inertia up to about 19,000 Ibs. A signif- icant portion of the heavy-duty gasoline vehicles are above 19,000 Ibs and will not be included in that study. Only a limited amount of chassis testing on heavy-duty gasoline vehicles has been conducted using the transient cycle; and even less data exists on engine versus chassis comparisons. In general, heavy-duty gaso- line chassis tests have not included unregulated emissions characterization. The virtual lack of emissions data in the heavy-duty gasoline vehicle category suggest that additional work in this area may be justified. Some vehicle categories that would be good candidates would include school buses, large box vans and soft drink and beer delivery trucks. •&U. S. GOVERNMENT PRINTING OFFICE: 1985/559-111/10751 ------- M. A. Warner-Selph andH. E. Dietzmann are with Southwest Research Institute, San Antonio, TX 78284. F. M. Black is the EPA Project Officer (see below). The complete report, entitled "Characterization of Heavy-Duty Motor Vehicle Emissions Under Transient Driving Conditions," (Order No. PB 85-124 154; Cost: $16.00, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, v'A 22161 Telephone: 703-487-4650 • The EPA Project Officer can be contacted at: Atmospheric Sciences Research Laboratory U.S. Environmental Protection Agency Research Triangle Park, NC 27711 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 BULK RATE POSTAGE & FEES PAID EPA PERMIT No G-35 Official Business Penalty for Private Use $300 ------- |