Abstract
A study has been made of the total engine friction, the piston assembly friction, and the unrecovered work done on the gases in a four-cylinder automotive engine cranked at low temperatures with its starter motor. Development of the instrumentation is briefly described, and the results obtained with a range of single and multigrade lubricating oils, at temperatures between 0 and 42°F, are given. The effect of oil viscosity (determined in a Ferranti–Shirley cone-and-plate viscometer) on the various losses was studied. Piston assembly friction, measured without the cylinder head in position, accounted for between 40 and 50 per cent of the engine friction and was predominantly viscous. The effect of pressure acting on the pistons was to increase the engine friction only slightly at the higher temperatures; unrecovered work done on the gases was a very important cause of cranking resistance and did not vary with oil viscosity. Shear stresses measured in the engine at the lower temperatures were higher than could be reached in the viscometer. The viscometer may, therefore, not have a general application for predicting the cranking resistance of non-Newtonian oils.
Published Version
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