IT is recognized that volumetric efficiency-and therefore specific output - can be increased by reduction in manifold temperature, pressure drops, and the like. The present investigation has been directed at the determination of the changes in volumetric efficiency which may be obtained by fuel-volatility variations. The results of this work may be summarized briefly as follows:
(1)
Very substantial improvement in engine performance can be obtained by taking advantage of suitable volatility increases.
(2)
A given degree of improvement in the distribution characteristics of a fuel can be attained by combining “front-end” and “total” volatilities in a fairly varied manner.
(3)
The distribution characteristics of a gasoline can be judged satisfactorily by using the amount evaporated at 158 deg. fahr. (A.S.T.M.) as a measure of “front-end” volatility and the temperature of the 90-per cent evaporated point as an index of “total” volatility.
(4)
It is possible to attain a marked degree of distribution improvement without resorting to extreme variations in either “front-end” or “total” volatility.
(5)
It appears that volatility improvements (properly chosen) constitute a real opportunity for increasing the usefulness of automobile fuels.
(6)
The improvement in the volatility characteristics of gasolines during the last four years has been much more marked than that which occurred during the entire ten years prior to 1931. The increasing and more intelligent application of the seasonal adjustment of fuel volatilities is indicated to be of real worth to the car operator. The actual value of “weather-wise” gasoline in the operation of a car is not generally appreciated but will become an increasingly important factor in induction-system design and improved engine-performance.
