EPA/ Industry Dynamometer Comparison Study Nine Vehicle Fleet Submitted to: Dynamometer Comparison Study Task Force April 1995 Martin Reineman Richard Nash United States Environmental Protection Agency National Vehicle and Fuel Emissions Laboratory 2565 Plymouth Road Ann Arbor, Michigan 48105 ------- Abstract Between October 1993 and September 1994 a test program was conducted at the EPA National Vehicle and Fuel Emissions Laboratory (NVFEL) to evaluate emission and fuel economy differences between tests conducted on a large single roll electric and a twin small roll hydrokinetic chassis dynamometers. The principal objective of the program was to compare emissions and fuel economy results from a twin 8.65 in. roll chassis dynamometer, adjusted per current EPA practice, to results obtained with the 48 in. electric dynamometer, which was adjusted to more closely duplicate actual on-road forces over a wide speed range (70 to 10 mph/hr). Because of concerns about how to phase-in a change in dynamometer design, a secondary objective of the study was to assess the accuracy of a dynamometer manufacturer's attempt to simulate twin roll hydrokinetic dynamometer characteristics on the electric dynamometer such that emission and fuel economy results would be similar between the two dynamometer designs. This report serves as a summary of the results. It is not intended to explain reasons for the observed differences or to address the various issues that may surround a change in dynamometer design for emission and fuel economy testing. Background This test program is one step in a series of events which occurred since the late 1980s to investigate the need for an improved method to simulate vehicle road operation using a chassis dynamometer. The 1990 Amendments to the Clean Air Act directed EPA to make changes to its current test practices, if appropriate, to be more representative of actual road operation. As a result, several cooperative studies were conducted between EPA and the American Automobile Manufacturers Association (AAMA) to determine whether a twin or single roll chassis dynamometer would best achieve the new test objectives. Through mutual agreement with the AAMA members, and with input from other vehicle manufacturers, equipment suppliers, and other interested parties, EPA adopted-a 48 in. single roll electric dynamometer design for Cold CO Emissions Regulations and has proposed that this design be adopted for future emission and fuel economy compliance testing. The results presented in this study follow from an EPA October 1992 public workshop attended by vehicle manufacturers, equipment suppliers, and other interested parties. It was agreed at the October meeting to form an EPA/Industry task force to design a test program to compare the results of changes in dynamometer designs and associated changes in test procedures. The Task Force consisting of representatives of EPA's Engineering Operations Division and Certification Division met several times with vehicle manufacturers and other interested parties to develop the test program design. ------- The basic test program consisted of exhaust emissions and fuel economy comparisons among an EPA 8.65 in. twin roll hydrokinetic chassis dynamometer, and two load setting methods using the EPA 48 in. single roll electric chassis dynamometer. Efforts were made to assure the representativeness of the two dynamometers, and to reduce the number of uncontrolled test variables. The number of tests per vehicle was first estimated using assumptions for typical emission and fuel economy variability and standard sample size design theory. In practice, the actual number of tests were based on an examination of an individual vehicle's emission and fuel economy variability, engineering judgment, and practical testing resource considerations. The basic test sequence consisted of a cold start FTP followed by a HFET test and a vehicle/dynamometer coast down. Summary Tables 1-A, 2-A, 1-B, and 2-B summarize the program results. Tables 1-A and 2-A present emission and fuel economy changes obtained using the large roll electric dynamometer relative to the current twin small roll hydrokinetic dynamometer. Table 1-A presents normalized results expressed in percent difference. Table 2-A presents absolute differences expressed in units of g/mi or mi/gal. These data suggest the changes in loading associated with the electric dynamometer were vehicle specific. In general, the data showed that testing a vehicle on the large single roll electric dynamometer resulted in higher exhaust emissions, similar FTP fuel economy, and lower HFET fuel economy relative to the twin small roll hydrokinetic dynamometer. Tables 1-B and 2-B summarize results of the secondary objective of the program, the attempt to modify the electric dynamometer load such that it would mimic the performance of the hydrokinetic dynamometer. These tables show the differences of the electric dynamometer relative to the hydrokinetic dynamometer, expressed as percent in Table 1-B, and as absolute differences in Table 2-B. These differences were vehicle specific, but in general still showed slightly higher emissions on the large roll electric, and higher FTP fuel economy relative to the twin small roll dynamometer. The Honda vehicle, the only manual transmission vehicle in the vehicle fleet, was unable to be tested on the electric dynamometer due to instability in the dynamometer's control circuitry when operated in the simulation mode. In addition to the uncertainty whether accuracy could be improved, the issue associated with modeling each vehicle's twin roll behavior using generic tire/roll slip characteristics was determined to be too large to warrant additional development. Test Design Test Site Description - Two dynamometers were used: D006, a Clayton Model ECE-50 with twin rolls, 78 in. long and a nominal 8.65 in. diameter, with 8875 Ib inertia simulation capability. Dynamometer D005, immediately adjacent to D006, is a Horiba Model LDV-48-86-125HP-AC electric chassis dynamometer, ------- with 24 in. wide single rolls with a nominal diameter of 48 in. and 6000 Ib inertia capability. Vehicle restraint on the twin roll dynamometer consisted of the EPA standard non-drive wheel chocks, cable restraint, and cross straps for front wheel drive vehicles on Dynamometer D006. The restraint system for D005 consisted of the GM designed front and rear bumper straps, with cross straps for front wheel drive vehicles. The EPA dynamometer video drivers' aids (VDA) were identical, as were the nominal 5300 cfm fixed speed cooling fans and cell supply air flow. Exhaust gas measurements were made using a shared analyzer site, A003, and a common, moveable, standard CVS, No. 29C, with nominal 350 cfm flow capacity. With exception of the 48 in. dynamometer, and the 8875 Ib inertia capability of the 8.65 in. dynamometer (versus 6875 Ib inertia capability for the most common test site at NVFEL), all equipment used for this study are fully representative of an EPA standard test cell used for compliance testing. Test Vehicles - The nine vehicle test fleet was selected by the Task Force and is described in Attachment A. These vehicles represent a compromise of a desire to select vehicles with a wide range of drive wheel configuration, road load, axle and inertia weights, and the desire to select vehicles representative of the current in-use fleet. Test Fuel - Certification test quality 96 RON test fuel was used for all emission tests. Test fuel analysis reports were provided to task force members when requested. Drivers - One driver operated a particular vehicle for all tests on both dynamometers. Driver training on the electric dynamometer for the four drivers used in the program consisted of practice tests to become familiar with the vehicle response when using the electric dynamometer. Driving excursions from the FTP and HFET cycles were monitored using standard FTP testing requirements as summarized by EPA's VDA summary, which is published with every emission and fuel economy test. Measurements - Exhaust emission measurements were reported for THC, CH4, NMHC, CO, NOx, and COg. Carbon balance fuel economy was calculated using standard procedures and measured test fuel properties. A test report summarizing these results was made available to the interested parties after the data were inspected using normal EPA quality control guidelines. The nine test vehicles were equipped with instrumentation for measuring a maximum of 16 channels of dynamometer and vehicle parameters. All vehicles were equipped with a volumetric fuel measuring system, and additional instrumentation at the vehicle sponsor's option. On several vehicles, this equipment included wheel torque measuring systems, and instrumentation for measuring wheel speed, engine speed, throttle position, and other vehicle specific parameters including multiple vehicle temperatures. ------- Dynamometer data collected for most, but not all tests, included the hydrokinetic dynamometer front and rear roll speeds, hydrokinetic dynamometer load cell force, electric dynamometer roll speed, and electric dynamometer load cell force. The vehicle/dynamometer parameters were measured and recorded at 10 Hz frequency by using Macintosh based LabView hardware and software. Vehicle Preparation - Vehicles were supplied with fuel tank drains, standard 2.5 in. ID exhaust connectors, and in some cases, a slave canister system to avoid evaporative emission influence on the emission test. Test Sequence - The basic test sequence for a typical vehicle using either dynamometer was as follows: Day 1 Drain fuel, fill to 40% of tank volume with pre-conditioning fuel. Prep LA-4 Purge slave evaporative canister if required Soak 12-24 hours Day 2 Push on dynamometer - no heat build FTP HFET (warm-up and sample) Coast downs - Hydrokinetic 55-45, Electric 70-10 Add test fuel to makeup for daily consumption (vehicle specific) Purge slave canister if required Soak 12-24 hours The typical test sequence began Day 1 activities on Monday, and repeated Day 2 events Tuesday through Friday. Emission, fuel economy, and coast downs on Tuesday through Thursday served as pre-conditioning for the following test day. Day 1 pre-conditioning for all test vehicles was performed on each Monday, or at the outset of the test program, or if there was a disruption in the week long test series for any given vehicle. The dynamometer test location was alternated between individual tests on D005 and D006 to cancel vehicle emission and fuel economy changes with time. Assignment of the vehicle/dynamometer test configuration and the daily testing order was based on site availability and the schedules of the personnel from the vehicle suppliers who often monitored their independent data acquisition systems or chose to witness the daily tests. Track Data Road Coast Down Data - Coast down tests on the nine vehicles were run at the Ford Motor Company Michigan Proving Grounds using instrumentation described in a draft SAE procedure, J1743. New tires were installed prior to the ------- track coast downs and stabilized with 1000 miles of track mileage accumulation. Coast down tests where run using a 75 to 5 mph velocity range and nominal ambient conditions of zero wind speed, 68 +/-10 F, and 29.0 +/- 2.0 in. Hg. It was the opinion of the Task Force that the tight range of ambient coast down temperature eliminated the need for an ambient temperature correction The single roll three term road load force equation was developed using methodology of draft SAE procedure J1743 and the 70 to 10 mph data, while the two term road load force equation and resulting 55-45 coast down time was derived using the methodology of EPA Advisory Circular No. 55C and the 60 to 20 mph data. Track and dynamometer load settings for the nine vehicle fleet are presented in Attachment C. None of the load settings for the single or twin roll dynamometers included an increase in loading for air conditioner simulation. Dynamometer Adjustments Hvdrokinetic - Load setting on the Clayton dynamometer was based on the EPA guidelines published in Advisory Circular No. 55C. Given the "target" 55-45 mph dynamometer coast down time, and Attachment B (an EPA procedure for adjusting loading on a twin roll dynamometer), a 50 mph actual power absorption setting was determined for each test vehicle. The 50 mph horsepower value for each vehicle was a two or three test average determined as a function of the repeatability of the procedure for the individual vehicle. Dynamometer tire pressure for passenger cars and trucks was set to 45 psi. Electric (True Road Load Simulation) - Standard Horiba dynamometer software was used to derive the dynamometer coefficients for each test vehicle from the track coefficients. This technique is described in the Horiba Dynamometer Operation Manual, under the section Coast Down - Derivation of dyno-setting road load parameters. Protocol for the load setting included: the dynamometer inertia was defined as the equivalent test weight (ETW) multiplied by 1.015, the target and actual force curves were produced by coasting down the vehicle from 70 to 10 mph with 5 mph speed intervals, the actual and target force curves were matched to within two pounds, and two verification runs were required to obtain final dynamometer coefficients. Dynamometer tire pressure was set at the same pressure used for track coast downs, which was based on vehicle manufacturers' recommended inflation pressure. Electric (Hydrokinetic Load Simulation) - Tests were performed using an electric dynamometer that was modified by Horiba Instruments to produce loading comparable to the hydrokinetic dynamometer. Modifications included hardware and software (version 1.34C TR) changes. Horiba experimented with two versions of the twin roll simulation during the program. The first version of the twin roll simulation was judged to be unsatisfactory after the first three vehicles were tested due to poor correlation between the twin roll and the twin roll ------- simulation results, and was replaced by a second version of the simulation, which was used to test eight of the nine vehicle fleet. A description of the second twin roll dynamometer simulation was not published. The electric dynamometer coefficients for the twin roll simulation tests were derived from a three run average of consecutive 60 to 10 mph coast downs on the hydrokinetic dynamometer following a HFET driving schedule (warm-up and sample). This was done to match the loading characteristics of the twin roll hydrokinetic dynamometer. The EPA VDA system was used to measure the speed/time data. These data were reduced to provide average coast down times for 5 mph speed intervals from 60 to 10 mph. Standard Horiba software was used to derive A, B, and C target force coefficients from the hydrokinetic dynamometer coast down data. These target force coefficients were used with the Horiba automated approach to determine dynamometer coefficients (over a 60 to 10 mph coast down range) to yield a second set of coefficients for the electric dynamometer. Dynamometer tire pressure was set using the same approach as described earlier for the true road load simulation tests. Quality Control Test Vehicles - Vehicle sponsors conducted emission and fuel economy tests to verify stability before delivery of the vehicles to EPA. D006 Representativeness - The representativeness of the D006 hydrokinetic dynamometer was based on EPA intra laboratory comparisons of 0006 diagnostic data, and emission and fuel economy results from EPA and AAMA repeatable test vehicles on dynamometer D006. EPA Intra laboratory repeatable vehicle (REPCA) tests consisted of weekly hot 505 second emission and fuel economy tests on dynamometers D001 through D006. D006 results were examined using standard control charting practices comparing it with D001-D004. These data were made available to task force participants before and during the test program. CVS. Analyzer Bench - The common analyzer bench and CVS for the test program were verified using CFR and EPA laboratory specific criteria. These included weekly TGI tests, daily CVS flow count checks, monthly analyzer curve verifications, daily analyzer checks using the EPA sample analysis correlation (SAC) checks, and monthly NCJ2 to NO converter efficiency checks. Hydrokinetic Dynamometer - The quality of the hydrokinetic dynamometer was maintained by weekly REPCA tests and CFR and EPA standard diagnostic checks. Electric Dynamometer - The operational integrity of the electric dynamometer was based on adherence to Horiba's recommended practices and ------- from suggestions from Task Force members. Attachment D describes the EPA diagnostic checks for the electric dynamometer during the comparison study. Weekly EPA REPCA tests were also run to assess emission and fuel economy repeatability. Precautions were exercised during the dynamometer comparison study so that the timing of calibration adjustments had a minimal impact on the results of thp etnrtv the study. Results The tabular and graphical data specific to the electric dynamometer are frequently described as "Road Simulation" or "Twin Roll Simulation". Road simulation refers to data obtained when the electric was used to simulate actual on-road loading conditions. Twin roll simulation describes the mode of operation of the electric when it was adjusted to simulate the twin roll hydrokinetic dynamometer loading. Tables 1 -A and 2-A present emission and fuel economy changes of the large roll electric dynamometer relative to the current twin small roll hydrokinetic dynamometer. Table 1-A presents normalized results expressed in percent difference. The Ford F-150 and Ranger trucks exhibited some of the greatest changes in emissions and fuel economy. Table 2-A presents absolute differences expressed in units of g/mi or mi/gal. Tables 1-B and 2-B present similar results for the twin roll simulation data. Figures 1-5 are displays of the percent difference between the electric and hydrokinetic dynamometers. Figures 1-5 compare the differences in HC, CO, NOx emissions, and FTP and HFET fuel economy, respectively. All differences are presented with respect to the hydrokinetic dynamometer. Figures 6-10 are similar presentations for results using the hydrokinetic simulation loading on the electric dynamometer versus the hydrokinetic baseline condition. Appendices 1-4 present the individual composite data and the individual bag 1, 2, and 3 values. Appendix 1 summarizes individual test results for the FTP and HFET road simulation results versus the hydrokinetic tests. Appendix 2 presents the data for the tests used to compare the hydrokinetic simulation to the hydrokinetic baseline. Note that the hydrokinetic baselines for individual vehicles in Appendices 1 and 2 are sometimes different because twin roll simulation tests were run after the road simulation tests, and therefore the hydrokinetic baseline was rerun to prevent confounding effects due to changes over time in the vehicle's emission and fuel economy performance. Appendices 3 and 4 are the individual test bag data. Appendices 5 and 6 summarize coast down data. Appendix 5 presents 55 to 45 mph coast down times for road simulation tests versus-the hydrokinetic ------- dynamometer data. Appendix 6 displays similar data for twin roll simulation tests on the electric dynamometer compared to the hydrokinetic data. Coast downs on the hydrokinetic dynamometer were the standard 55 to 45 mph quick check, while coast downs on the electric were from 70 to 10 mph for the road simulation tests on the electric, and from 60 to 10 mph for coast downs utilizing the simulation mode of the electric. Appendix 7 contains plots of coast down road load force curves for the nine vehicle test fleet. Each figure includes a plot derived from the 75 to 5 mph track force loading (labeled "Track"), the 70 to 10 mph force loading on the electric used for road simulation tests (labeled "Single Roll"), and the hydrokinetic dynamometer load from 60 to 10 mph (labeled "Twin"). The plots are least squares fits of the reduced track and dynamometer coast down data extrapolated to 0 mph. The two dynamometer force curves include dynamometer load and friction at the tire/roll interface. The lower half of each figure also includes a plot of the difference in loading between the two dynamometers. Ninety-five percent confidence intervals around the absolute means for emissions and fuel economy are displayed in Appendices 8 and 9. Confidence intervals in Appendix 8 are specific to the road simulation mode of the electric versus the hydrokinetic baseline. Appendix 9 refers to similar summaries for the simulation mode of the electric versus the hydrokinetic baseline. The plots in Appendices 8 and 9 are interpreted as showing statistically significant differences at the 95 percent confidence level if the confidence intervals do not overlap. Discussion Road Simulation Results - Tables 1-A, 2-A, Figures 1-5, and Appendix 8 all suggest that, in general, when adjusted to reproduce on-road loading conditions, vehicles tested on the electric dynamometer showed higher exhaust emissions, similar FTP fuel economy, and lower HFET fuel economy relative to the hydrokinetic dynamometer. An examination of the data shows that the dynamometer influence is quite vehicle specific. Individual vehicles showed higher, lower, or no change in exhaust emissions and fuel economy. Twin Roll Simulation Results - Tables 2-A, 2-B, Figures 6-10, and Appendix 9 again suggest a vehicle specific response to twin roll simulation on the electric dynamometer. In general, CO emissions were biased higher on the electric, as was FTP fuel economy. As previously stated, the manual transmission Honda vehicle could not be tested on the electric dynamometer due to feedback stability in the twin roll simulation control circuitry which caused the vehicle to shake severely in the 15-20 mph speed range as the transmission was shifted into second gear. An informal consensus of the Task Force was that significantly more development work was necessary, without certainty of success, to have confidence that the twin roll simulation could produce emissions and fuel economy similar to the hydrokinetic dynamometer on a vehicle specific basis. ------- Coast Down Data - An inspection of the 55-45 mph coast down data in Appendices 5 and 6 show that the loaded coast down times had lower coefficients of variation for seven of nine vehicles in road simulation mode, and lower variation in twin roll simulation mode for six of eight vehicles, relative to the twin roll results. Force Curve Plots - Track and dynamometer road force curves are plotted in Appendix 7. They show that the coast downs performed on the electric dynamometer more accurately matched the measured track coast down force versus velocity data than coast downs performed on the hydrokinetic dynamometer. When reviewing only the hydrokinetic coast down data, it can be noted that the rear wheel drive vehicles more accurately matched the track road load, while the front wheel drive vehicles tended to overload at low speed and underload at speeds above about 50 mph. Conclusions Three conclusions are developed from the data in this study: 1) When the 48 in. single roll electric dynamometer was operated in road simulation mode, exhaust HC, CO, and NOx emissions were generally higher, FTP fuel economy results were similar, and HFET fuel economy results were lower relative to the 8.65 in. twin roll hydrokinetic dynamometer. 2) The emissions and fuel economy differences of the nine vehicle fleet attributable to the change in dynamometer design and loading were vehicle specific. 3) It was the Task Force's opinion that the twin roll simulation did not accurately estimate the loading of the twin roll hydrokinetic dynamometer, and that significantly more development work would not guarantee better accuracy. / Acknowledgments EPA wishes to express its appreciation to the many individuals in the motor vehicle and dynamometer industries who supported this project; it could not have succeeded without the high level of cooperation which was received. All aspects of this endeavor, from planning to the preparation of this report, benefited from the cooperation received. While naming specific individuals runs the risk of inadvertently omitting someone, EPA wishes to thank those members of the task force listed below as well as other unnamed members of their firms who assisted in this effort: ------- Individual Firm Giedrius Ambrozaitis Ken Barnes Peter Benkmann Bob Bisaro Frank Buckley Ken Burt Tommy Chang Charles Cowham Severino D'Angelo Todd Fagerman Anastas Farjo Todd Fronckowiak Robert Gower Mark Guenther Steve Hunter Paul Karas John Keefe Chuck Kizlauskas Dianna Korduba-Sawicki Alan Kuge Brooke Lament Dave Luzenski Ted Malachowski Bill Mears Richard Pearl Dave Perkins Dave Pruess David Robertson Bob Slater Dan Sougstad Kim Waggoner William Watkins Allen White Mercedes-Benz Froude Mercedes-Benz Ford Buckley Associates General Motors Honda Burke-Porter Horiba Ford Ford Ford Chrysler Ford Ford Ford General Motors Ford Ford Honda Clayton General Motors Suzuki Horiba Toyota Froude Chrysler Ford Mercedes-Benz General Motors Nissan Schenck-Pegasus Chrysler Acknowledgment is also made to the efforts of all the EPA staff who contributed to the test program, including Bob Gilkey and the test site technicians: Phil Conde, Ken Lesage, Dave VanAmburg, and Paul Velandra. ------- Attachment A Dynamometer Comparison Study Test Fleet Vehicle Model cubic inches Ford F-150 Mercedes 300E Cadillac DeVille Toyota Truck Ford Ranger Nissan 240SX Dodge Caravan Chevrolet Lumina Honda Civic 1992 1987 1991 1991 1993 1991 1992 1992 1992 300 159 300 183 140 146 201 189 92 A-4 A A-4 L-4 A-4 A-4 A-4 A-4 M-5 Rear Rear Front Rear Rear Rear Front Front Front pounds 1861 1761 2427 3122 1140 1409 2345 2232 1442 Firestone Pirelli Michelin Bridgestone Firestone Toyo Goodyear Goodyear Goodyear 1 M W VXI*_Wr P235/75R15 I95/65VR16 P205/70R15 185/R14LT P195/70R14 195/60R15 P205/70R15 P215/60R16 P175/70R13 ------- Attachment B EPA/Industry Dynamometer Comparison Study Procedure for 8.65 in. Twin Roll DPA Determination 1. Drain tank and fill to 40% of volume. Record the time and date on the Dynamometer Power Absorption Determination data sheet. 2. Weigh the front axle, rear axle, and total vehicle. Record this on the data sheet and attach the weigh scale print out. Notify test requester of weight results before proceeding. 2.1 Total weight must be within 100 Ibs of production vehicle weight. 2.2 Drive axle weight must be within 50 Ibs of production axle weight. 3. Fill the drive axle tires to 5 psi above the vehicle manufacturer's dynamometer tire test pressure. Record tire data on the data sheet. 4. Park the vehicle in the soak area for a minimum of 4 hours to stabilize the tire temperature. Record the initial and final soak times on the data sheet. 5. Prepare the vehicle and dynamometer. 5.1 Drive the vehicle onto the dynamometer. 5.2 Position front cooling fan and driver's aid, adjust the tie-down cable to normal tension. 5.3 Reduce the tire pressure to 45 +/- 1 psi for passenger cars, or the vehicle manufacturer's dynamometer tire test pressure +/- 1 psi for trucks. 5.4 Position a side cooling fan if used by the manufacturer for conventional HFET tests. 5.5 Set the dyno inertia weight and manufacturer AHP from the DPA data sheet. Verify proper flywheel engagement. 5.6 Select the rear roll position on the dynamometer speed/power meter. 5.7 Select the Automatic and Count positions on the quickcheck timer. (Steps 5.6 and 5.7 will permit measurement of front roll quickcheck time). 6. Warm-up the vehicle and dyno by driving an HFET (warmup and sample). 7. Begin coastdown measurements within 1 minute of the end of the HFET, / 7.1 Accelerate at an approximate rate of 2 mph/sec to about 65 mph and hold that speed for about 2 seconds. 7.2 Verify that the quickcheck timer has reset to zero. 7.3 Shift the vehicle transmission to neutral. 7.4 Allow the vehicle to coastdown to 40 mph. 7.5 Repeat Steps 7.1 through 7.4 until 3 coastdowns (not necessarily consecutive) have been obtained within a range of 0.3 seconds. Do not run more than 5 coastdowns. Record all values on the data sheet. 8. When 3 coastdowns are completed at the load setting in Step 5.5, increase or decrease the actual horsepower settings, and repeat Steps 7.1-7.5. In order, set actual horsepowers equal to +0.5 HP, -0.5, +1.5, -1.5, +1.0, and -1.0 above and below the manufacturer's DPA value. Record the thumbwheel settings on the data sheet. 9. Complete the DPA data sheet and submit to the test requester for processing. ------- Attachment C Track and Dynamometer Loading Conditions Twin Roll Vehicle Ford F-150 Mercedes 300E Cadillac DeVille Toyota Truck Ford Ranger Nissan 240SX Dodge Caravan Chevrolet Lumina Honda Civic Track Coefficients A B . C 21.8 40.4 15.9 54.9 33.3 48.1 27.1 26.9 15.4 0.9315 0.3529 0.4716 0.5983 0.1642 0.0096 0.4804 0.4216 0.1384 0.03266 0.01636 0.02444 0.03058 0.02903 0.01809 0.02494 0.01637 0.01960 Electric Dynamometer Coefficients Taraet Time ABC 55-45 mnh. sec 12.11 13.41 4.91 16.28 13.77 23.71 3.16 8.73 4.60 0.1108 0.2089 -0.0538 0.2812 0.11 13 -0.3065 0.1921 0.0392 0.0105 0.04090 0.01688 0.02467 0.03152 0.02842 0.02001 0.02662 0.01888 0.01982 13.97 17.55 17.96 15.13 14.25 15.43 16.50 19.07 16.30 Test Weight. pounds 4500 3750 3875 5250 3500 3125 4000 3625 2500 Actual Hp @ 50 mph 14.1 6.9 6.6 11.8 11.0 6.5 7.8 4.6 6.9 Note: A, B, and C track and dynamometer coefficients are expressed in units of Ibf, Ibf/mph, and lbf/(mph)(mph), respectively. ------- Attachment D Electric Dynamometer Operational Checks Frequency Description Daily: Warm-up Procedure Auto Calibration Test Vehicle-Off Coast Down at Test Condition Weekly: Parasitic Loss Check Timing Test 1500 and 5500 Ib Vehicle-Off Coast Downs Zero Load Speed Check Monthly: Lubricate Roll Cover Tracks Inspect Roll Brake Lines Clean Air Filters on CDC-900 and Power Converter Cabinets ------- Table 1-A Dynamometer Comparison Study Emissions and Fuel Economy Differences of 48 in. Single Roll Electric Dynamometer Relative to 8.65 in. Twin Roll Hydrokinetic Dynamometer, % Ford F-150 Mercedes 300E GM Cadillac Toyota Truck Ford Ranger Nissan 240SX Dodge Caravan GM Lumina Honda Civic N 8 6 6 7 8 4 7 8 7 HQ 25 1 12 5 9 18 -2 25 7 QQ 46 20 19 0 70 58 9 35 17 NOx 40 7 0 7 17 5 22 10 15 FTPFE -0.6 1.4 1.1 0.1 -2.0 -0.1 2.7 1.1 -0.2 HFETFE -5.1 -0.6 -4.5 -2.2 -7.2 -0.9 -4.3 -4.8 -1.9 Notes: N equals number of FTP tests on the single roll. Number of FTP tests on the twin roll are approximately the same. Electric dynamometer matches actual road force from 70 to 10 mph. ' Hydrokinetic dynamometer uses standard load curve. % = ((Single roll - Twin roll)/(Twin roll))100 2/2 ------- Table 2-A Dynamometer Comparison Study Emissions and Fuel Economy Differences of 48 in. Single Roll Electric Dynamometer Relative to 8.65 in. Twin Roll Hydrokinetic Dynamometer Ford F-150 Mercedes 300E GM Cadillac Toyota Truck Ford Ranger Nissan 240SX Dodge Caravan GM Lumina Honda Civic N 8 6 6 7 8 4 7 8 7 HC g/mi 0.064 0.003 0.017 0.007 0.014 0.036 -0.004 0.063 0.007 CO g/mi 0.74 0.59 0.37 0.01 3.86 1.72 0.12 1.29 , 0.16 NOx g/mi 0.206 0.021 -0.001 0.016 0.014 0.024 0.093 0.037 0.028 FTP mi/aal -0.09 0.28 0.20 0.02 -0.44 -0.01 0.54 0.21 -0.07 HFET mi/< -1.25 -0.18 -1.45 -0.49 -2.19 -0.33 -1.36 -1.63 -0.98 Notes: N equals number of FTP tests on the single roll. Number of FTP tests on the twin roll are approximately the same. Electric dynamometer matches actual road force from 70 to 10 mph. Hydrokinetic dynamometer uses standard load curve. Applicable emission standards - Mercedes 300E, GM Cadillac, Nissan 240SX, GM Lumina, Honda Civic HC = 0.41 CO = 3.4 NOx = 1 .0 Ford F-150, Toyota, Dodge Caravan HC = 0.80 CO = 10.0 NOx = 1.7 Ford Ranger HC = 0.80 CO = 10.0 NOx = 1.2 ------- Table 1-B Dynamometer Comparison Study Emissions and Fuel Economy Differences of Electric Dynamometer Twin Roll Simulation Relative to 8.65 in. Twin Roll Hydrokinetic Dynamometer, % Ford F-150 Mercedes 300E GM Cadillac Toyota Truck Ford Ranger Nissan 240SX Dodge Caravan GM Lumina Honda Civic N 6 5 8 7 7 6 6 6 0 HQ 3 4 8 6 0 -7 4 0 -2 QQ 19 1 1 8 12 -16 10 3 -7 NOx -1 10 -2 2 -3 0 3 2 FJPFE 1.2 1.9 2.0 3.2 3.6 1.3 0.5 -0.7 HFETFE -0.3 2.8 1.5 1.8 2.5 0.3 -0.1 -1.3 Notes: N equals number of FTP tests on the single roll. Number of FTP tests on the twin roll are approximately the same. Honda could not be tested on the single roll. Electric dynamometer matches hydrokinetic load from 60 to 10 mph. Hydrokinetic dynamometer uses standard load curve. % = ((Single roll - Twin roll)/(Twin roll)) 100 ------- Table 2-B Dynamometer Comparison Study Emissions and Fuel Economy Differences of Electric Dynamometer Twin Roll Simulation Relative to 8.65 in. Twin Roll Hydrokinetic Dynamometer Ford F-150 Mercedes 300E GM Cadillac Toyota Truck Ford Ranger Nissan 240SX Dodge Caravan GM Lumina Honda Civic N 6 5 8 7 7 6 6 6 0 HC g/mi 0.008 0.010 0.011 0.008 -0.010 0.007 0.001 -0.005 CO a/mi 0.27 0.37 0.16 0.17 -0.78 0.30 0.04 -0.23 NOx g/mi -0.006 0.030 -0.011 0.004 . -0.003 0.001 0.012 0.009 FTP mi/gal 0.19 0.41 0.35 0.48 0.80 0.31 0.10 -0.15 HFET miA -0.08 0.86 0.48 0.38 0.74 0.10 -0.04 -0.45 Notes: N equals number of FTP tests on the single roll. Number of FTP tests on the twin roll are approximately the same. Honda could not be tested on the single roll. , Electric dynamometer matches hydrokinetic load from 60 to 10 mph. Hydrokinetic dynamometer uses standard load curve. Applicable emission standards - Mercedes 300E, GM Cadillac, Nissan 240SX, GM Lumina, Honda Civic HC = 0.41 CO = 3.4 NOx = 1.0 Ford F-150, Toyota, Dodge Caravan HC = 0.80 CO = 10.0 NOx = 1.7 • Ford Ranger HC = 0.80 CO = 10.0 NOx =1.2 2/27.35 ------- |