1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (724) 772-8512 FAX: (724) 776-0243TO PLACE A DOCUMENT
3、 ORDER: (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1998 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、ndardJ2438ISSUEDDEC1998Issued 1998-12Low-Temperature Cranking Load Requirements of an EngineAir Starter Method1. ScopeThe air cranking system components, which include the tank, valve, hose, and starter, must becarefully selected to provide the necessary speed to start an engine under the most sever
5、e climatic conditionsfor which the system is intended. Engine cranking loads increase with cold temperatures, therefore, the initialselection of these components, needs to consider low-temperature engine torque requirements. To insure anadequate air cranking system is obtained, it is important that
6、proper test procedures are used for obtaining thecranking load requirements of the engine.2. References2.1 Applicable PublicationsThe following publication forms a part of this specification to the extent specifiedherein. Unless otherwise indicated, the latest issue of SAE publications shall apply.2
7、.1.1 SAE PUBLICATIONAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J300Engine Oil Viscosity Classification2.2 Related PublicationsThe following publications are provided for information purposes only and are not arequired part of this document.2.2.1 SAE PUBLICATIONSSAE J12
8、53Low Temperature Cranking Load Requirements of an EngineSAE J2437Air Starter Motor Test Procedure3. Description3.1 Engine PreparationThe engine to be tested should be equipped with all accessories that provide parasiticloads, such as, power steering pump, automatic transmission, gear motor sets, et
9、c.3.1.1 The engine, if new, should be “run in“ to stabilize friction loadsequivalent to 2400 km (1500 miles) or 18 hat normal engine speed.3.1.2 The engine is winterized with antifreeze solution for the temperature at which the test will be run.SAE J2438 Issued DEC1998-2-3.1.3 The engine oil selecte
10、d for the low-temperature test should be representative of the high limit viscosity for theSAE grade recommended by the engine manufacturer for the operating temperature range (refer to SAEJ300). Sufficient oil of the same viscosity should be obtained for the complete test program so variations inte
11、st results can be minimized.3.1.4 Fuel dilution of the engine oil will reduce its viscosity; therefore, to avoid this possibility, the cranking test isrun without fuel in the carburetor, or with the fuel system cut off.3.1.5 To prepare the engine for the test, the engine is warmed up and oil drained
12、 hot. This procedure should berepeated two times to assure complete change of oil when oil grade change is made. The oil filter ischanged for the final fill. When the same grade of oil is used for other test temperatures and/or additionaltest days, the engine warm up procedure is repeated and only o
13、ne drain is required.3.1.6 Install a thermocouple in the center of the greatest mass of oil, so soak temperatures can be monitored.3.1.7 Equip engine with necessary instrumentation to provide cranking speed starter inlet pressure, tank pressure,air flow (optional).3.1.8 Prior to starting the cold so
14、ak period, warm up the engine for approximately 5 to 10 min to circulate oil, runcarburetor bowl dry and disable ignition or cut off fuel system, and adjust throttle plate to the idle position.3.1.9 The engine with the calibrated motor is soaked at the test temperature for a period of 16 to 24 h, wh
15、ich canbe monitored by the oil thermocouple.3.2 Cranking Motor PreparationThe cranking motor is used to measure the engine cranking torque. Tominimize performance variances, a new cranking motor should be “run in“ until the motor performancebecomes stabilized prior to calibration which is determinin
16、g the speed, torque, and starter inlet pressure underload. Air flow can be used in some cases to provide a data accuracy cross check. After completion of thecranking load tests, a re-calibration curve should be run to verify initial performance.NOTESince torque is proportional to cranking motor air
17、inlet pressure, determination of engine torque can becalculated by obtaining the cranking motor running torque corresponding to the cranking motor air inletpressure and rpm from the performance characteristics of the calibrated cranking motor andmultiplying this value by the proper flywheel ring gea
18、r to cranking motor pinion gear ratio.3.3 Cranking Load Tests3.3.1 A sufficient number of cranking tests should be run to obtain a curve of average torque versus averageengine speed over an approximate range of 30 to 120 engine rpm for gasoline engines, 50 to 150 rpm fordirect injection diesel engin
19、es, and 120 to 220 rpm for small indirect injection diesel engines.3.3.2 To obtain the range of speeds required to plot the torque curve, the air inlet pressure is varied. Air should notbe cold soaked for this test. The air source should be within 5 C (77 F) of the air temperature used tocalibrate t
20、he cranking motor to minimize differences in energy supplied to the motor.3.3.3 The cranking time for each test should be approximately 5 s with the readings between 0 and 5 s used as theplotting points. Allow a minimum of 30 min additional soak time before performing the next cranking test.3.3.4 Us
21、ing the test data, calibrated cranking motor performance characteristics and engine ring gear to crankingmotor pinion gear ratio, calculate the engine torque requirements for each test speed and plot an enginetorque requirement curve.SAE J2438 Issued DEC1998-3-3.3.5 It should be noted that since gea
22、r efficiencies have been neglected, the torque measured is not true enginetorque but that as seen by the cranking motor. However, this is the correct torque for design and applicationdata for determining cranking motor requirements.3.3.6 Once the engine torque requirement curve has been determined a
23、nd the speed required to start the engineis known, cranking motor performance requirements for the engine application can be determined.3.3.7 A correctly sized air cranking system should provide a minimum of 5 s cranking time above themanufacturers minimum unaided cranking speed at the minimum unaid
24、ed start design temperature. The 5 scrank duration represents the capacity from a 60 gallon air tank on a vehicle with a typical air starting system.The minimum cranking speed is generally between 100 and 120 rpm. Engine manufacturers recommendstarting aids below 4 C (40 F), however, end users expec
25、t unaided starts above 7 C (20 F).PREPARED BY THE SAE STARTER MOTOR STANDARDS COMMITTEESAE J2438 Issued DEC1998RationaleA need for a document that is specific to low-temperature cranking load requirements for airstarters is addressed with this specification. A similar document that addresses electri
26、c starters is SAEJ1253.Relationship of SAE Standard to ISO StandardNot applicable.ApplicationThe air cranking system components, which include the tank, valve, hose, and starter, must becarefully selected to provide the necessary speed to start an engine under the most severe climaticconditions for
27、which the system is intended. Engine cranking loads increase with cold temperatures,therefore, the initial selection of these components needs to consider low-temperature engine torquerequirements. To insure an adequate air cranking system is obtained, it is important that proper testprocedures are used for obtaining the cranking load requirements of the engine.Reference SectionSAE J300Engine Oil Viscosity ClassificationSAE J1253Low Temperature Cranking Load Requirements of an EngineSAE J2437Air Starter Motor Test ProcedureDeveloped by the SAE Starter Motor Standards Committee
