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3、 ORDER; (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1992 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICESubmitted for recognition as an American National Sta
4、ndardJ2177ISSUEDAPR92Issued 1992-04CHASSIS DYNAMOMETER TEST PROCEDUREHEAVY-DUTY ROAD VEHICLESForewordThis Document has not changed other than to put it into the new SAE Technical Standards BoardFormat. The Definition Section was changed to Section 3.TABLE OF CONTENTS1. Scope . 21.1 Field of Applicat
5、ion 22 References 22.1 Applicable Publications. 23. Definitions 24. Test Equipment. 34.1 Test Facility. 34.2 Chassis Dynamometer . 44.3 Instrumentation. 55. Test Procedure . 65.1 Vehicle Preparation 65.2 Operating Conditions 75.3 Test Measurements 85.4 Instrumentation and Equipment Removal 96. Data
6、Correction 96.1 Reference Test Conditions . 96.2 Power Corrections 96.3 Correction Factor Calculations . 97. Data Analysis . 137.1 Additional Units and Symbols. 137.2 Determination of Observed Wheel Power 137.3 Calculation of Corrected Wheel Power. 137.4 Calculation of Expected Wheel Power 137.5 Com
7、parison of Corrected to Expected Wheel Power . 147.6 Set Point Determination 14SAE J2177 Issued APR92-2-7.7 Vehicle Speed Calculation 147.8 Additional Diagnostic Considerations .158. Presentation of Results. 158.1 Recorded Test Data 158.2 Reported Test Information 161. ScopeThis SAE Recommended Prac
8、tice has been adopted by SAE to specify:a. A standard procedure for chassis dynamometer testing of heavy-duty road vehicles for the purpose ofdetermining power delivered through the drive tires.b. A method of correcting observed power to reference test conditions.c. A method of analyzing the test da
9、ta to determine if the test results are within expected power ranges.1.1 Field of ApplicationThis document is applicable to DOT Class 6, 7, and 8 on and on/off highway heavy-dutyroad vehicles equipped with compression ignition engines, manual or automatic transmissions, and single ortandem rear driv
10、e axles.2. References2.1 Applicable PublicationsThe following publications form a part of the specification to the extent specifiedherein. Unless otherwise indicated the latest revision of SAE publications shall apply.All terminology, test procedures, reference conditions and correction procedures a
11、re in accordance with SAEJ1995 except where otherwise specified by this document.SAEJ1587Joint SAE/TMC Electronic Data Interchange Between Microprocessor Systems in Heavy-Duty Vehicle ApplicationsSAEJ1708Serial Data Communications Between Microprocessor Systems in Heavy-Duty VehicleApplicationsSAE J
12、1995Engine Power Test CodeSpark Ignition and Compression IgnitionGross Power Rating 3. DefinitionsThis section contains the definition of key terms used to describe the chassis dynamometer testprocedure.3.1 Gross Brake PowerThe power of an engine when configured with only the built-in equipment requ
13、ired forself-sustained operation in accordance with SAE J1995. This does not include accessory power as defined in3.2.3.2 Accessory PowerPower required to drive engine or chassis components that are necessary to perform theintended service or that power auxiliary systems. These components normally i
14、nclude the chassis inlet andexhaust systems, cooling fan, alternators/generators, vacuum pumps, power steering pumps, and air and freoncompressors, operating as described in Sections 4 and 5. All engine or chassis parasitic power lossesincurred during the chassis dynamometer test that are not includ
15、ed in the gross brake power shall for thepurpose of this procedure be considered accessory power.3.3 Flywheel PowerThe power of an engine as installed in the chassis and measured at the flywheel. Flywheelpower is the net difference between gross brake power and accessory power.3.4 Drive Train Effici
16、encyThe ratio of the sum total of the power delivered to all drive wheels to the flywheelpower. This includes power losses generated by the transmission, driveshaft, carriers, and axles. It does notinclude tire rolling resistance losses. Drive train efficiency may vary with the speed of the vehicle
17、as well as theamount of torque transmitted. It is normally supplied by the vehicle component manufacturer.SAE J2177 Issued APR92-3-3.5 Rolling Resistance PowerThe power required to overcome the rolling resistance of all drive tires. Thispower normally varies with the type of tires, tread pattern, in
18、flation pressure, vehicle weight on the drive tires,vehicle speed, and/or dynamometer roller surface.3.6 Tire-Roller Slip PowerThe net difference between the power delivered through the drive tires and thattransmitted to the dynamometer rollers. This power loss is due to tire to roller relative slip
19、 and is normallydissipated as heat. Tire-roller slip power can be significant and may vary with the type of tire, tread pattern,inflation pressure, roller surface, roller diameter, as well as the test speed and torque application.3.7 Observed Dynamometer PowerThe observed vehicle power with no corre
20、ctions made as measured by thechassis dynamometer using the equipment and procedures defined in Sections 4 and 5.3.8 Dynamometer Machine LossesThe net difference between the power delivered to the dynamometer rollersand that measured by the dynamometer load cell. These include windage or bearing pow
21、er losses as well asany unaccounted for load cell calibration error.3.9 Observed Wheel PowerThe observed dynamometer power adjusted only for dynamometer machinelosses, if any. If these losses are not known and cannot be accounted for, then observed wheel power isassumed equivalent to observed dynamo
22、meter power.3.10 Corrected Wheel PowerThe observed wheel power corrected to reference test conditions.3.11 Expected Wheel PowerThe vehicle power that would normally be expected to be transmitted to thedynamometer if the test were run at reference test conditions. This is calculated by subtracting es
23、timatedaccessory, drive train, and rolling resistance power losses from the engine gross brake power.3.12 Reference Test ConditionsThe standard or reference test conditions to which all power corrections aremade per 6.1. These corrections are made to reference engine inlet air and fuel conditions as
24、 well as toaccount for tire-roller slip.3.13 Reference Test SpeedThe highest engine speed that can be attained in direct drive gear with the throttlefully depressed and the dynamometer rollers turning, but fully unloaded. At the reference test speed theobserved dynamometer power should be at or near
25、 zero and tire-roller slip power is assumed to be negligible,since there is little or no torque transmitted to the dynamometer.3.14 Set Point SpeedThis is also sometimes referred to as the governor cut-in speed. It is the speed abovewhich the engine governor begins to significantly reduce engine pow
26、er. The set point speed is normallyspecified to preclude governor interference with engine power at nominal rated speed and is therefore normallyset at slightly above rated speed.3.15 Low and High Idle SpeedsThe lowest and highest test engine speeds respectively that can be attained withthe clutch f
27、ully disengaged (pedal depressed). At all idle speeds flywheel power is limited to zero. The throttlepedal is not depressed at low idle and is fully depressed at high idle. Low and high idle speeds are measuredwith all engine accessories driven at minimum output levels.4. Test EquipmentThis section
28、describes the recommended test equipment necessary to perform the chassisdynamometer test.4.1 Test Facility4.1.1 The use of an indoor facility is recommended in order to effectively control ambient test air and fueltemperatures, which can significantly effect vehicle power. The test facility should
29、be able to control ambientair temperature to within 25 C 15 C.SAE J2177 Issued APR92-4-4.1.2 The test facility should be equipped with a fresh air ventilation system of sufficient capacity to maintain anadequate air supply to the test vehicle. Ambient air pressure must be maintained at a constant le
30、vel in thetest facility throughout the chassis dynamometer test.4.1.3 The facility should be equipped with an exhaust ventilator system that permits engine exhaust gas to beremoved directly from the test room. This ventilator tube is normally vented to atmosphere, or to separatereservoir, either of
31、which must have a total pressure of within 0.75 kPa of the ambient air pressure in the testfacility.4.1.4 The test facility should be equipped with safety chains and mounts for the test vehicle rear axle as well as tie-down straps for the front wheels. Chocks are acceptable for the front wheels only
32、 if the drive tires cradle orare cradled by the dynamometer rollers. The safety chain mounts should be positioned so as to minimize thedownward force on the test vehicle when the chains are installed, resulting in an undesirable increase inrolling resistance. Ideally the safety chain mounts should a
33、llow the chains to be positioned as close tohorizontal as possible, provided they prevent lateral movement of the test vehicle during operation.4.1.5 For vehicles having engines equipped with chassis mounted air-to-air charge air cooling systems, it isrecommended that a portable auxiliary cooling fa
34、n be available. This cooling fan should be placed directly infront of the radiator on any chassis dyno tests where the inlet manifold air temperature exceeds therecommended test limits as described in 5.2.6.4.1.6 The test facility must also be equipped with other safety equipment as required by the
35、dynamometermanufacturer, facility owner, or appropriate federal, state, and local codes. This would normally include, butnot be limited to, a fire extinguisher, safety glasses, ear protection, etc.4.2 Chassis Dynamometer4.2.1 A computer based dynamometer automatic control and data acquisition system
36、 is recommended, but notrequired. This type of dynamometer can be used to automatically control test cycles and acquire, analyze,plot, and report data. Such dynamometer control systems can generally improve test uniformity,repeatability, and overall accuracy levels as well as reduce operator error a
37、nd fatigue.If the test dynamometer does not have the capability to analyze the test results in accordance with Sections6 and 7, it is recommended that a PC based computer program be used to analyze the test results. Refer tothe engine or vehicle manufacturer for this program. In such cases observed
38、test data would manually beentered into the program in order to calculate corrected and expected wheel power levels.4.2.2 The chassis dynamometer should be designated by the manufacturer for use in this type of testing. Thedynamometer must be of the non-portable variety designed to measure whole veh
39、icle horsepower at thedrive tires on single and tandem axle heavy-duty road vehicles. The expected wheel power should notexceed the dynamometer manufacturers stated power absorption capabilities.4.2.3 On tandem drive axle vehicles, the chassis dynamometer must be capable of adjustment as required to
40、maintain proper tire-roller contact on all drive tires of the test vehicle.4.2.4 Whenever possible large diameter dynamometer rollers are recommended in order to increase tire-rollercontact area and reduce the possibility of large tire-roller slippage power losses and tire overheating. A rollerdiame
41、ter of 0.9 m (36 in) or greater is recommended, although a minimum roller size of 0.5 m (20 in)diameter is permitted. On any test where excessive tire-roller slippage or tire overheating is apparent asdescribed in 5.2.8, a set of auxiliary or “slave“ test drive tires is also recommended.SAE J2177 Is
42、sued APR92-5-4.2.5 The test dynamometer should be calibrated by a method approved by the manufacturer at periodic intervals.On many dynamometers this is a dead weight load cell calibration check only. In such cases the calibrationperiod is not to exceed every 6 months. Prior to conducting each chass
43、is dynamometer test, check to insurethat this calibration period has not expired.The dynamometer calibration should also include accounting for bearing, windage, or other machine losses.On certain dynamometers these losses can be measured and automatically included in the observeddynamometer power r
44、eading. In such cases observed dynamometer power will be equal to observed wheelpower. If these losses are not automatically included in the test dynamometer calibration, then they shouldbe accounted for in accordance with 7.2.4.3 Instrumentation4.3.1 The following minimum test measurements and inst
45、rumentation accuracy is recommended for the chassisdynamometer test at each test point:a. Engine Speed 0.2% of measured valueb. Dynamometer Speed 0.2% of measured valuec. Observed Dynamometer Power 1.0% of measured valued. Fuel Flow 1.0% of measured valuee. Inlet Fuel Temperature 2.0 Cf. Inlet Air T
46、emperature 2.0 Cg. Inlet Manifold Air Temperature 2.0 Ch. Inlet Fuel Pressure 2 kPai. Inlet Manifold Pressure 2 kPa4.3.2 On vehicles equipped with tandem drive axles, where each axle drives a separate set of rollers (either singleor paired), dynamometer speed measurements must be obtained for both a
47、xle-roller sets. Ondynamometers so equipped, observed dynamometer power should also be recorded for each set of rollers.Observed dynamometer power is then corrected individually for each drive axle in accordance with 7.3.4.3.3 The following measurements and instrumentation accuracy should be taken o
48、nly once at some convenientpoint immediately before, during, or after the dynamometer test:a. Fuel Density 0.001 kg/l (0.2 API)b. Fuel Viscosity (optional) 0.1 mm2/sc. Barometric Pressure 0.1 kPad. Vapor Pressure (optional) 0.1 kPa4.3.4 Fuel viscosity and ambient air vapor pressure measurements are
49、optional. If measured, they will improve theaccuracy of the correction factors used in Section 6 to calculate corrected wheel power. Note, however, thatfuel viscosity is only critical on pump-line-nozzle (P-L-N) injection systems; therefore it is not necessary tomeasure on test engines equipped with unit injectors.4.3.5 The use of the standard vehicle tachometer to obtain engine speed is generally not recommended becausethe accuracy level required per 4.3.1 cannot normally be obtained. Engine and dynamometer speed value
