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Engine and Transmission Lubricant Viscosity Effects on Low Temperature Cranking and Starting
ISSN: 0148-7191, e-ISSN: 2688-3627
Published February 01, 1969 by SAE International in United States
Annotation ability available
Engine oil and automatic transmission fluid viscosities are major factors in assuring good starting and running performance in cold weather. To determine the contributions of the engine and transmission to the cranking and running effort, instantaneous torque and power, obtained with an instrumented engine-transmission apparatus, were determined for five engine oils ranging in viscosity from 4 to 184 poise (SAE 5W to SAE 20W) and for four transmission fluids ranging in viscosity from 3200 to 83,000 cp at -20 F. Specific engine and transmission cranking variables - engine friction, compression and expansion, engine rotational inertia, and transmission friction and rotational inertia - were analyzed in detail.
The engine required most of the cranking effort, which increased with increasing engine oil viscosity. Increasing engine oil viscosity increased engine friction torque but decreased engine friction power because of decreased cranking speed. Net cylinder torque input to the cylinder air, a result of compressing and expanding air in the cylinder, decreased with decreasing cranking speed. Both engine and transmission inertia could be neglected for most cranking conditions.
A thermodynamic analysis of the cranking process revealed that cranking speeds should be high for good starting because heat losses from the cylinder gases are low and cylinder gas pressures and temperatures are high.
A crankability factor, defined as the ratio of instantaneous engine friction torque to cranking speed, indicated that engine crankability deteriorated drastically as engine oil viscosity increased above about 30 poise and starter motor stall was being approached.
Results obtained with the engine-transmission apparatus were corroborated by results obtained in car tests. In general, starting and running improved as the engine oil and transmission fluid viscosity were lowered. Transmission performance was unsatisfactory with fluid viscosities greater than 30, 000 cp, as a result of inadequate fluid flow. Because of engine stall, a transmission fluid viscosity less than 3200 cp is desirable for low temperature running.
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CitationHaviland, M., "Engine and Transmission Lubricant Viscosity Effects on Low Temperature Cranking and Starting," SAE Technical Paper 690768, 1969, https://doi.org/10.4271/690768.
- HammA. A., “Cold Factors on Cold Starting.” Published in SAE Progress in Technology, Vol.10; “The Role of Engine Oil Viscosity in Low Temperature Cranking and Starting,” New York: Society of Automotive Engineers, Inc., 1966.
- Private communication with W. A. Sterling, Michigan Automobile Club.
- GravesW. H., MougeyH. C., and UphamE. W., “Winter Oils for Automobile Engines.” SAE Transactions, Vol. 29 (1934).
- BlackwoodA. J., “The Performance of Engines at Low Operating Temperatures.” SAE Journal, Vol. 36 (1935), p. 70.
- LowtherH. V., MeyerW. A. P., SelbyTheodore W., VickG. K., “Development of Research Technique for Determining the Low-Temperature Cranking Characteristics of Engine Oils.” Published in SAE Progress in Technology, Vol. 10, “The Role of Engine Oil Viscosity in Low Temperature Cranking and Starting,” New York: Society of Automotive Engineers, Inc., 1966.
- “Research Technique for Determining the Low-Temperature Cranking Characteristics of Engine Oils.” CRC Report No. 414, March 1968.
- “Determination of Low-Temperature Cranking Characteristics of Engine Oils at - 20 F Using CRC L-49-663 Research Test Technique.” CRC Report No. 405, January 1965.
- SelbyT. W., VerduraT. M., and HunstadN. A., “A Study of Engine Oils at Low Temperatures in an Improved Cranking Apparatus.” Published in SAE Progress in Technology, Vol. 10, “The Role of Engine Oil Viscosity in Low Temperature Cranking and Starting,” New York: Society of Automotive Engineers, Inc., 1966.
- BarringtonR.and LutwycheB. A., “The Petrol Engine and Its Friction.” Institution of Mechanical Engineers Proc. General Discussion on Lubrication and Lubricants, Vol. 1, October 1937.
- “Basic Considerations in the Combustion of Hydrocarbon Fuels with Air.” National Advisory Committee for Aeronautics, Report 1300, 1957.
- AndersonR. L.and HunstadN. A., “Dexron Automatic Transmission Fluid.” Published in SAE Activity Proceedings, “Fuel and Lubricants 1968 Papers,” New York: Society of Automotive Engineers, Inc., 1969.
- SelbyT. W., “Automatic Transmission Fluid Viscosity at Low Temperature, and Its Effect on Transmission Performance.” SAE Transactions, Vol. 68 (1960).
- PikeW. C. and HaisellO., Proceedings of Institution of Mechanical Engineers, Vol. 181, Part 3, C, 1966-1967, pp. 177-183.