Electrically Driven Automotive Air Conditioner

<div class="section abstract"><div class="htmlview paragraph">In automotive air conditioning systems, compressor is used to convert low pressure low temperature refrigerant into high pressure high temperature refrigerant. Various types of compressors like swash plate, rotary vane, scroll etc. are widely used in the automotive industry for air conditioning applications.</div><div class="htmlview paragraph">In rotary vane compressors, thermal protector is used as a safety device, designed to prevent the compressor from overheating during refrigerant compression process. When the discharge temperature exceeds the preset limit of thermal protector, the thermal protector will activate and stop the electrical supply to compressor clutch to stop the compressor operation thereby preventing potential damage to air conditioning system, engine, and other nearby parts of the vehicle.</div><div class="htmlview paragraph">This technical paper explores the various real-world scenarios for a hot country like India, which may result into higher discharge temperatures of compressor resulting into activation of thermal protector. The research encompasses vehicle level evaluations, replicating real world operating scenarios or misuse scenarios that may be evaluated for a vehicle with different load conditions of the air conditioning system and environmental conditions to consider the deletion of thermal protector from the system. The results of this analysis will be imperative in identifying the conditions that must be evaluated to justify the elimination of thermal protector in a particular compressor, assuring that the system's reliability and safety remains intact.</div></div>

<div class="htmlview paragraph">As a prelude to the assessment of the global warming impact of automotive air conditioning, fundamental scientific facts about global warming are reviewed. A comprehensive mathematical model is next developed to quantify the total equivalent warming impact (TEWI) of the automotive air conditioning. Using this model, intensive calculations are performed to determine the TEWI of the present R-134a air conditioning system as well as the proposed alternate systems. The calculated results indicate that TEWI of the present R-134a system is higher than those of the flammable subcritical systems (R-152a, R-290 and R-717) but lower than those of the supercritical carbon dioxide system (R-744) and open air (R-729) cycle system. The calculated results show that TEWI of 303 million R-134a automotive air conditioning systems in the worldwide fleet is no more than 0.14% of TEWI of the greenhouse gases emitted annually into Earth's atmosphere due to human activity. According to the TEWI reduction cost estimates developed by the Council of Economic Advisers to the U. S. President, the cost of eliminating automotive air conditioning TEWI should not exceed $12.60 per system over its life span of 12 years. Taking cognizance of the miniscule contribution of automotive air conditioning to the global emissions and the acceptable cost to eliminate them, it is concluded that the most felicitous and cost effective solution to deal with the automotive air conditioning TEWI is to continue to improve the existing R-134a system through reduction of the refrigerant emissions and enhancement of the overall system efficiency.</div>

<div class="htmlview paragraph">The production unit number of small diesel engine cars tends to decline except recreational vehicles in Japanese market in recent years, while the production unit number in Europe market keeps on increasing owing to the merits of the durability and the fuel consumption. The small diesel engines will have to be improved in the near future by solving major problems such as noise and vibration pollution, environmental pollution, improvement in performance of diesel engines, in order to expand the production of the engines.</div> <div class="htmlview paragraph">This paper refers to a basic study on the experimental and analytical methods for the reduction of resonant vibration in each vibration mode on some cylinder blocks of small high-speed diesel engines in rated engine speed range. Hammering test method, which is easy and useful for measuring frequency response functions, is carried out in the experiments. In this test, the cylinder blocks are directly excited with the impulse hammer, and more the main journals are excited via the newly-made force transmission parts in the next experiment. Two kinds of the engines which have been recently recognized as low noise and vibration engines are chosen in this study. The cylinder blocks of the engines are called of long skirt type and ladder frame type, respectively. The vibration characteristics of these cylinder blocks are obtained in the frequency range from 500 <i>Hz</i> to 2 <i>kHz</i> using the experimental modal analysis. This frequency range is chosen in consideration of the reliability of the vibration experiments. And the force transmission routes from the piston heads to the crank journals of each cylinder block are considered as mentioned in the latter experimental method. The experimental results are used to calculate the natural frequencies by the modal analysis and the calculated results are compared with the ones obtained from FEM analysis. Furthermore, the cylinder blocks are remodeled in order to reduce the vibrations of all modes using FEM analysis.</div> <div class="htmlview paragraph">Consequently, it has been shown that the vibration stress of the cylinder block can be reduced by higher rigidities and more lightening weights of the crankcase and the crank journals in the measured frequency range.</div> <div class="htmlview paragraph">The conclusions are described as follows;</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts is useful to measure the natural frequencies of a cylinder block. This method can be easy to get the equal results with the measured ones on running conditions without engine operation.</div> </li> <li class="list-item"> <span class="li-label">2</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts can easily analyze the natural frequencies at all the vibration modes on equal conditions with running ones. Then the method is a useful tool for improving the vibration characteristics.</div> </li> <li class="list-item"> <span class="li-label">3</span> <div class="htmlview paragraph">It has been proved from the analytical viewpoints that the cylinder block of the ladder frame type can be adopted as low-noise, small diesel engines with little increase of the engine weight while maintaining higher rigidity.</div> </li> </ol> </div>

<div class="htmlview paragraph">Recent research on internal combustion spark ignited engines has focused more and more on charge control by means of direct injection.</div> <div class="htmlview paragraph">Nevertheless most of the systems proposed so far do not seem to be suitable for small engines as they are high-cost.</div> <div class="htmlview paragraph">A new direct injection system, based on the hydraulic phenomenon commonly known as “water hammer” has been recently proposed by the authors to be used for small two-stroke engines.</div> <div class="htmlview paragraph">It constitutes a reliable means of achieving high injection pressures while maintaining the simple manufacturing and low-cost characteristics of this kind of engines. It is equipped with a low-pressure fuel pump and provides high injection pressure values thanks to the conversion of the kinetic energy of the fluid into a local pressure rise, which takes place when the fuel flow is suddenly halted by an automatic valve.</div> <div class="htmlview paragraph">The first results from a simulation code which takes into account of cavitation and column separation phenomena typical of the system's behaviour are presented.</div> <div class="htmlview paragraph">The influence of various parameters on system's performances is discussed.</div>

<div class="htmlview paragraph">A method of real time oil concentration measurment has been developed utilizing the effect of ultraviolet light absorption by lubricating oil in the liquid refrigerant line of an automotive air conditioning system. The light wavelengths from 200nm to 370nm are selected based on the ultraviolet light absorption sensitivity of the oils and refrigerants (CFC12,HFC134a).</div> <div class="htmlview paragraph">The effects of temperature,pressure and contaminantion on the absorbance of light are investigated in order to determine how these parameters affect the concentration measurement. The density changes of refrigerants are then compensated in the calculation for the oil concentration. The uncertainties of the overall concentration measurement are less than ±0.1 weight percent at 1 weight percent concentration.</div> <div class="htmlview paragraph">A transient oil circulation of the automotive air conditioner is measured by using this method.</div>

<div class="htmlview paragraph">The increase of the electrical power required by current vehicles suggests the need to evaluate its impact on fuel consumption, emissions and performances.</div> <div class="htmlview paragraph">Moreover, due to the growing amount of cars equipped with Air Conditioning System, a deep knowledge on how these additional loads influence vehicle performances is required.</div> <div class="htmlview paragraph">Often, the mechanical power requested by electrical and AC systems is comparable to the mechanical power necessary to move the vehicle (or sometimes even higher) and this happens mainly during urban driving cycles.</div> <div class="htmlview paragraph"><i>Drivetrain 3.0</i> is an integrated simulation model for vehicle energetic evaluation and management; fuel consumption and performances on a generic speed vs time driving cycle are dynamically evaluated as a function of electrical power loads and their possible management strategies.</div> <div class="htmlview paragraph">Other additional mechanical loads (i.e. climate compressor) and the related transmission efficiency could also be taken into account.</div> <div class="htmlview paragraph">Furthermore, <i>Drivetrain 3.0</i> can calculate the fuel consumption as a function of the state of charge (SOC) of the battery and the engine idle rpm boost (depending on the energy management strategies), in order to guarantee the electrical balance.</div> <div class="htmlview paragraph">The simulation model enables the evaluation of the effects of Start&Stop strategy on fuel consumption, taking into account the electrical power consumption when the engine is switched off.</div>

<div class="section abstract"> <div class="htmlview paragraph">This document provides preliminary<sup><span class="xref">1</span></sup> safety-relevant guidance for in-vehicle fallback test driver training and for on-road testing of vehicles being operated by prototype conditional, high, and full (Levels 3 to 5) ADS, as defined by SAE J3016. It does not include guidance for evaluating the performance of post-production ADS-equipped vehicles. Moreover, this guidance only addresses testing of ADS-operated vehicles as overseen by in-vehicle fallback test drivers (IFTD).</div> <div class="htmlview paragraph">These guidelines do not address:</div> <ul class="list disc"> <li class="list-item"> <div class="htmlview paragraph">Remote driving, including remote fallback test driving of prototype ADS-operated test vehicles in driverless operation. (Note: The term “remote fallback test driver” is included as a defined term herein and is intended to be addressed in a future iteration of this document. However, at this time, too little is published or known about this type of testing to provide even preliminary guidance.)</div></li> <li class="list-item"> <div class="htmlview paragraph">Testing of driver support features (i.e., Levels 1 and 2), which rely on a human driver to perform part of the dynamic driving task (DDT) and to supervise the driving automation feature’s performance in real time. (Refer to SAE J3016.)</div></li> <li class="list-item"> <div class="htmlview paragraph">Closed-course testing.</div></li> <li class="list-item"> <div class="htmlview paragraph">Simulation testing (except for training purposes).</div></li> <li class="list-item"> <div class="htmlview paragraph">Component-level testing.</div></li></ul> <div class="htmlview paragraph">These guidelines also do not address prototype vehicle and IFTD performance data collection and retention. The collection of data invokes various legal and risk management considerations that users of this document should nevertheless bear in mind, such as:</div> <ul class="list disc"> <li class="list-item"> <div class="htmlview paragraph">Maintaining auditable procedures and documentation.</div></li> <li class="list-item"> <div class="htmlview paragraph">Adhering to applicable privacy laws and principles.</div></li> <li class="list-item"> <div class="htmlview paragraph">Ensuring adequate data collection and recording integrity to support post-crash forensic analysis.</div></li></ul></div>

<div class="section abstract"><div class="htmlview paragraph">In recent years the 2-wheelers engines companies have been focused on increasing the overall engine efficiency, that can be achieved amongst other by engine down-speeding, engine down-sizing and by reducing the frictions; however, to maintain or improve vehicle performance, it is necessary to provide a corresponding increase in specific power.</div><div class="htmlview paragraph">In accordance with these trends, the studied approaches and methodologies have been exploited, during the development of the new Piaggio small scooter engine.</div><div class="htmlview paragraph">In this work a multi-objective analysis has been applied to the valve train system design, in order to optimize the engine performance in terms of friction reduction, power curve and timing system response. Along with this optimization methodology, a robust design has been studied to make the peak cranking compression pressure insensitive to the engine starting device working. These calculation methodologies have been followed using commercial software as GT-SUITE® code and the modeFRONTIER® platform for the multi-objective optimization analysis.</div><div class="htmlview paragraph">The several configurations investigated have allowed to reach the desired trade-off between the appropriate and efficient valve train behavior and the engine performances.</div><div class="htmlview paragraph">The global engine friction reduction has been obtained thanks to low resisting cam torque profiles, a specific valve springs set and a new compression releaser device (during engine starting phase).</div><div class="htmlview paragraph">The results have been further validated by an experimental campaign carried out on the test bench for engine performance and on the specific cold test bench to evaluate friction losses.</div></div>

<div class="htmlview paragraph">In the past decade, SCR deNOx technology with urea injection has grown to maturity. European OEMs will apply SCR deNOx to meet future heavy-duty emissions legislation starting with EURO-4 (2005/2006). Numerous research programs in Europe and the US have shown a variety of system layouts and control strategies. The main differences are formed by:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">the engine-out NO<sub>x</sub> calibration</div> </li> <li class="list-item"><div class="htmlview paragraph">the application of an NO to NO<sub>2</sub> catalyst</div> </li> <li class="list-item"><div class="htmlview paragraph">open-loop or closed-loop urea dosage control.</div> </li> </ul> </div> <div class="htmlview paragraph">This paper gives an overview of possible SCR system configurations that are required for different stages of future emission legislation.</div> <div class="htmlview paragraph">Engine-out NO<sub>x</sub> emission is strongly influenced by ambient conditions. Projections in this study show that a combination of cold climate and a wintergrade fuel is the most severe: it may lead to 30% lower engine-out NO<sub>x</sub> emission with respect to laboratory conditions. The varying engine-out NO<sub>x</sub> emission requires a safety margin in the case of an open-loop controlled system in order to avoid excessive NH<sub>3</sub> slip.</div> <div class="htmlview paragraph">Calculations in this paper show that Euro 4 limits can be met with open-loop controlled urea dosage; an NO to NO<sub>2</sub> catalyst is even not required. For other future emission legislation (Euro 5, US 2007 and US 2010), it becomes difficult to safely achieve the limits with open-loop control. US 2007 and 2010 legislation require an NO to NO<sub>2</sub> catalyst because of the low average load and consequently low exhaust gas temperatures. Engines that are developed to meet US 2010 legislation need special measures to increase the exhaust gas temperature and to reduce engine-out NO<sub>x</sub> below 2 g/kWh.</div> <div class="htmlview paragraph">In all cases, optimal hydrolysis and mixing conditions are of major importance. High speed photography and droplet size measurements are presented as methods for characterizing and modeling aqueous urea spray patterns. The information from these measurements is used as input parameters for simulation tools. These consist of a 2D/3D CFD program for urea mixing analysis and a 1D SCR system model for development of dosage control and optimization of catalyst dimension.</div> <div class="htmlview paragraph">Finally, simulations with the SCR system model are compared with measurements on the engine test bench.</div>

<div class="htmlview paragraph">Recyclable content of motor vehicles is presently 75%, by weight, the majority of which is iron based components. Approximately 9% of the vehicle weight is in the form of various plastics. Today these materials are shredded and landfilled as automotive shredder residue (ASR). General Motors is putting greater emphasis on recycled automotive component systems through the use of the following environmental principles to guide the design and manufacture of our vehicles:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1.</span> <div class="htmlview paragraph">General Motors is committed to actions to restore and preserve the environment.</div> </li> <li class="list-item"> <span class="li-label">2.</span> <div class="htmlview paragraph">General Motors is committed to reducing waste, conserving resources, and recycling materials at every stage of the product life cycle.</div> </li> <li class="list-item"> <span class="li-label">3.</span> <div class="htmlview paragraph">General Motors is committed to the development and implementation of new materials and process technologies to enable rapid disassembly of component systems at the end of the vehicles' useful life.</div> </li> </ol> </div> <div class="htmlview paragraph">Additional forces driving recycling efforts stem from:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1.</span> <div class="htmlview paragraph">The reduction in the number of landfills.</div> </li> <li class="list-item"> <span class="li-label">2.</span> <div class="htmlview paragraph">Anticipated future legislation aimed at the recycled content of future vehicles.</div> </li> </ol> </div> <div class="htmlview paragraph">This technical presentation contains information and descriptions of recyclable instrument panel systems. Examples of three potentially recyclable instrument panel systems will be discussed. <b>Attention</b> will be given to design flexibility, quality, and costs for automotive components manufactured from processes utilizing these materials.</div>

<div class="htmlview paragraph">The Indian motorcycle and scooter market is faced with the combined challenge of exhaust emissions control from the environmental perspective and fuel economy demands from the consumer. Indian motorcycles are unique in their strong focus on reduced fuel consumption and this has resulted in the development of engines with quite different combustion characteristics in comparison to their European and ASEAN counterparts.</div> <div class="htmlview paragraph">Aprilia, Peugeot and Piaggio have recently released new scooter models utilizing air assist direct injection on their small 2-stroke engines to meet the ever increasing pressure on exhaust emissions, fuel economy and performance. These new scooter models are achieving good acceptance with the customer due to their combination of superior performance and improved fuel economy.</div> <div class="htmlview paragraph">Recent investigations by Orbital on Indian scooters and motorcycles show that the air assist direct injection system can be applied to Indian 2-stroke engines to meet the Indian 2005 emissions requirements without a catalyst and simultaneously provide a 30-35% fuel economy improvement on the Indian Driving Cycle (IDC). These results are superior to today's good 4-stroke fuel economy motorcycles and advance the 2-stroke motorcycle to best in class fuel economy status.</div> <div class="htmlview paragraph">Investigations have also been conducted by Orbital regarding the application of this air assist direct injection system onto Indian 4-stroke motorcycles. This study has shown good results with a fuel economy improvement of 12-15 % over the current levels. This is a unique achievement and is potentially more cost effective than the fitment of port injection systems when considering the fuel cost saving available with air assist direct injection.</div> <div class="htmlview paragraph">System descriptions, engine and vehicle performance, fuel economy and emissions capability test data are discussed in the following pages.</div>

<div class="section abstract"><div class="htmlview paragraph">The present paper outlines the selection and numerical modeling of a high performance and efficient blower motor fitted in an automotive Heating ventilation and air conditioning (HVAC) system. In today’s scenario blower motor is present in almost every car whether fitted with AC system or only blower system. The selection of a blower motor is very important in terms of delivering right amount of airflow with minimum consumption of electric power. As the power consumption goes up it may impacts in indirect green house gas (GHG) emission from a vehicle. While it does so e.g. fulfills HVACs’ airflow need, it generates some amount of heat which is very detrimental for its life and overall performance as well. Also the generated heat may lead to increase in temperature of the main stream air flow causing reduction in the cabin cooling and eventually hampers the comfort level.</div><div class="htmlview paragraph">The present study describes the methodology of selecting an automotive blower motor and its thermal modeling by using computational fluid dynamics (CFD). It involved the two different alternative methods of selecting the motor with the help of motor characteristics, fan characteristics and system resistance. The later method was adopted in selecting the motor in current study while the system resistance was evaluated numerically. Motor torque was estimated and electric power consumption was derived. Further to this the motor was modeled in CFD in detailed with its internal components like brush, commutator, armature etc. and then airflow and thermal analysis were carried out by conjugate heat transfer. Heat generated by the motor was modeled by source term. A detailed investigation in terms of airflow and temperature distribution was carried out to figure out the motor temperature rise. The simulation results was validated with that of experimental results and found a good correlation. Thus a methodology is developed with which designer can select and package the motor in order to have minimum power consumption and maximum life.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Electric vehicle thermal management system is essential for electric vehicles to guarantee cabin thermal comfort and battery appropriate operating temperature. As a matter of fact, in such systems, high- and low-temperature driving conditions can severely affect system performance, in terms of overall efficiency and driving range. In this context, an effective thermal management solution both for cabin thermal comfort and battery heating/cooling is investigated in this paper.</div><div class="htmlview paragraph">A key innovation is the deep integration of the HVAC and battery heating/cooling circuits. Primarily, in winter scenario, the heat generated by the powertrain during operation is used to warm the cabin, thereby mitigating the necessity for additional electric cabin heating. This way, despite the inclusion of an extra heat exchanger, a consistent amount of heat can be recovered and the use of the battery energy for electrical heating activation is significantly reduced, as already presented by the authors in a previous study. Furthermore, the HVAC sub-system is designed so as to streamline hot or fresh air to the battery for heating or cooling purposes, respectively, resulting in a comprehensive and integrated solution that enhances overall energy efficiency, with minimum penalizations in cabin comfort.</div><div class="htmlview paragraph">This evaluation employs a 1-D model of the HVAC and battery heating/cooling integrated circuit and a 0-D model to interface it with the vehicle powertrain. A second order electrical equivalent circuit model is employed for the battery, to better capture transient behavior and heat generation, with all the parameters in the model being temperature-and SoC-dependent. Different control strategies are proposed for the management of the thermal system and various driving conditions, including scenarios during summer and winter with different speed profiles, are taken into account to assess their performance.</div><div class="htmlview paragraph">It is important to note that while this integrated approach introduces a degree of complexity, the benefits in terms of energy efficiency are shown to be substantial if the system control logic is designed properly. This multi-faceted analysis contributes valuable insights to the ongoing discourse on optimizing electric powertrains for enhanced performance and efficiency under diverse operating conditions.</div><div class="htmlview paragraph">The analysis carried out allows to effectively determine the influence of the HVAC sub-system on the battery state of charge, and then in terms of driving range, i.e. for the Helsinki driving cycle, the deactivation of the cabin heating allows the increase of about the 30% the driving time. It has been also highlighted how the different control strategy can influence the average battery temperature and as a consequence its internal resistance especially during winter scenario. Due to the high thermal load required during the summer driving conditions, the control strategy seems to be less effective.</div></div>

<div class="section abstract"> <div class="htmlview paragraph">The SAE J3211 procedure applies to squeal evaluation for foundation brakes using single-ended inertia dynamometers for friction couples used on vehicles with regenerative braking systems. This document applies to squeal noise occurrences for on-road passenger cars and light trucks with a gross vehicle weight rating of 4536 kg or below and with at least one rechargeable energy storage system as a source for propulsion. The procedure incorporates aspects related to (a) minimum inertia dynamometer capabilities, (b) fixture requirements and setup, and (c) test sequences with emphasis on brake temperatures, brake pressure profiles, and strategies to represent brake blending.</div> <div class="htmlview paragraph">For this document, squeal occurs when the peak noise level is at least 70 dB(A) between 1.25 and 16 kHz for tests using full suspension corners or complete axle assemblies, or between 2 and 16 kHz for brakes not using an entire suspension corner.</div> <div class="htmlview paragraph">Test facilities intending to use this document, building on their expertise in conducting SAE J2521, shall review in detail the changes to test parameters (mainly brake temperatures and brake pressures) for legacy modules.</div> <div class="htmlview paragraph">This document also applies to vehicles with electromechanical braking systems to actuate the foundation brake. The test requester and the test facility are responsible for converting the hydraulic pressure levels into their equivalent clamping forces for brakes using electromechanical actuation.</div> <div class="htmlview paragraph">Before using this document for chassis dynamometer testing, review in detail the specifics related to at least (a) instrumentation, including in-cabin microphones; (b) threshold levels for noise detection; (c) temperature control priority between the front and rear axles; (d) vehicle loading and load distribution; (e) cooling air and environmental conditioning; (f) detailed terminology and labeling of channels and sensors; and (g) the regenerative settings and the state of charge during the test.</div> <div class="htmlview paragraph">Before using this document along with other methods to recreate the regenerative brake blending (e.g., Software-in-the-Loop or Hardware-in-the-Loop), consider (a) the vehicle powertrain, blending architecture and its applicable models, (b) actual profiles intended to recreate (e.g., control strategies, state of charge, test scenarios), and (c) actual embodiment of the simulation and integration with the native controls of the brake dynamometer.</div> <div class="htmlview paragraph">This document does not include noise from other sources (e.g., parking brakes, electric machines, driveline components).</div> </div>

<div class="section abstract"> <div class="htmlview paragraph">This SAE Recommended Practice is intended as the definition of a standard test, which may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use.</div> <div class="htmlview paragraph">The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems.</div> <div class="htmlview paragraph">The specific purpose of this document is to define a µPVT Test for the evaluation of the variation of wet friction system performance as a function of speed, temperature, and pressure. This procedure is intended as a standard for both suppliers and end users.</div> <div class="htmlview paragraph">The only variables selected by the supplier or user of the friction system are:</div> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">a</span> <div class="htmlview paragraph">Friction material</div></li> <li class="list-item"> <span class="li-label">b</span> <div class="htmlview paragraph">Fluid</div></li> <li class="list-item"> <span class="li-label">c</span> <div class="htmlview paragraph">Reaction plates</div></li></ol> <div class="htmlview paragraph">These three variables must be clearly identified when reporting the results of this test. If any of the test parameters or system hardware as described in this document are changed, other than the friction material, test fluid, or reaction plates, the data may not be reported as having been obtained using this document.</div> <div class="htmlview paragraph">This procedure is intended to evaluate the midpoint, endpoint, and breakaway coefficients and endpoint/midpoint ratios. The procedure can be used to demonstrate changes that occur between the different levels of engagement speed, sump temperature, and apply pressure. Refer to SAE J2487, SAE J2488, or SAE J2489 for coefficient variations due to changes in power level.</div> <div class="htmlview paragraph">The procedure, as described in detail in <span class="xref">Table 1</span>, consists of four 50 cycle break-in levels at 3500 rpm with increasing steps of apply pressure, followed by 16 levels consisting of 25 dynamic engagements, and one breakaway following completion of the 25th dynamic cycle. The 16 levels are achieved by varying initial engagement speed, apply pressure, and oil sump temperature while the inertia is kept constant at 0.701 kg/m<sup>2</sup>.</div></div>