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THE present wartime rationing of gasoline has jolted those of us who drive cars into a realization that those cars, in most cases, are not being driven as efficiently as possible. Out of this realization has come the desire to get as many miles per gallon from our rationed fuel as we possibly can, even at the cost of lower power, slower acceleration, and not quite as smooth a running engine as we have been accustomed to in the past. One of the suggestions that has been made for getting more miles per gallon out of our present engines is to “split” the engine, using only one-half of the cylinders for power. This paper is a résumé of the results of a test program carried out by the Bendix Aviation Corp. to explore the possibilities of the split engine.

IN the discussion of automatic devices in motor cars presented in this paper, special emphasis is placed on fully automatic and semi-automatic clutches, drives, and transmissions. Two methods of attack are being used to eliminate the clutch pedal: power operation of the mechanical clutch and the fluid coupling. Three fundamental types of control for vacuum-operated clutches are discussed: 1. Position or follow-up type valving. 2. Balanced or pressure-sensitive type. 3. Balanced cushion with variable bleed. In a review of the merits and demerits of the fluid coupling, fuel economy and the shock loads on the driving mechanism are stressed. An appraisal of the operating principles and characteristics of various fully and semi-automatic transmissions compares the following: overdrive; four-speed semi-automatic transmission with fluid coupling; three-speed fully automatic transmission; and four-speed fully automatic transmission with fluid coupling.

THIS paper reviews the experience of one company over a period of years in developing its product to give better fuel economy in spite of the demand for increased performance and the rising trend of car weight which has been occasioned by advance styling and appearance items. The data presented indicate how air-fuel ratios have been improved and compression ratios increased over a period of years, and some of the other factors influencing fuel economy. The effects of compression-ratio increase are discussed along with the use of higher-octane fuel and the necessity of proper choice of performance factors to obtain maximum benefit of these factors to get the best economy. Among other things discussed are the effect of high versus lower performance factors and the effect of different rear-axle gear ratios.

THIS paper develops the theme that streamlining is practical if, and only if, the power-supply system is engineered to fit the body. The author shows that the reduction in road-load power required brought about by streamlining may be accompanied by a less favorable engine specific fuel rate unless the transmission system is altered to prevent this result. The quantitative importance of this efficiency change is brought out, and the potential gains are set forth. The present state and future limitations of streamlining as a source of economy are treated, and test-car results are quoted. The economies to be realized are stated to come from the lower horsepower required to maintain a given engine speed. The importance of car weight and cross-sectional area are brought out, as well as the necessity for maintaining the accelerating ability of the streamlined car along with its improved economy.

AS the supplier of fuel energy for highway transportation, the petroleum refiner has the problem of producing gasolines on a mass-production basis which will be satisfactory in many types of engines operated under widely different driving conditions. This problem is complicated by the complex chemical and physical characteristics, both of the raw materials with which the refiner must work and of his finished products. This paper reviews the refiner's solution to this problem from the viewpoint of the transportation and maintenance engineer, and discusses the trends of the major characteristics of gasoline, namely, volatility, antiknock quality, sulfur content, gum content, and chemical composition. It suggests that the design of future engines will be in the direction of units of smaller size, having higher compression ratios, yielding higher power output and greater fuel economy, and requiring fuels of higher antiknock properties.

IMPROVEMENT in the control of smoke in the automotive diesel engine can be brought about by the use of lighter fuels of suitable ignition quality in cases where either design, maintenance, or adjustment fail to accomplish the degree of smoke control desired, the authors conclude. But this control is accomplished by some reduction in power and a loss in fuel economy. They suggest taking the power loss required for smoke control by means of resetting the smoke stop adjustment while retaining the advantage from an economy standpoint of the higher Btu per gal of the heavier fuel. The satisfactory performance of the heavier fuels in European bus operation clearly shows that smoke control can be effected by other means than resorting to fuels approaching kerosene in volatility.

OF the many characteristics of diesel fuels, heating value, ignition quality, and possibly fuel viscosity are the only important ones affecting engine power and economy, the authors disclose. In their paper they present data obtained from an extended fuel research program concerning the power and fuel economy obtained when using fuels differing in their physical and chemical characteristics. The points which seem to the authors to be of greatest practical significance are summarized as follows: 1. Assuming complete combustion, fuel volatility affects the pints per brake horsepower-hour only indirectly as it is related to heating value and ignition quality. 2. Most present-day engines have fixed injection timing and, on such engines, ignition quality is a major factor in determining volumetric fuel economy in the upper speed ranges. At the lower engine speeds, heating value in terms of Btu per gal, or as estimated from API gravity, is the most important consideration. 3.

SYMPATHIZING with the engineer who finds that the high efficiency designed into his engine fails to produce the anticipated increase in average miles per gallon obtained under normal driving conditions, the authors touch upon some of the factors, many of them out of the engine designer's control, which may completely mask the expected improvement. In so doing, they start with an engine of known specific consumption and show the effect of air resistance, chassis friction, gear ratio, and car weight on constant-speed road economy, comparing calculated values with actual test values available. Also discussed are such factors as climatic variations, traffic operation, cross-country driving and the individual driver, which have a definite effect upon economy, but over which the designer has little or no control. The effect of these factors is illustrated by the spread in tank mileage shown by a number of cars of similar model in fleet operation.

METHODS of increasing engine output are discussed, and supercharging is said to involve few difficulties. The location of the blower drive as it affects frequency and gear loading is considered. Bearing-load diagrams are analyzed for a high-speed and a low-speed engine. Tests indicate a negligible increase in piston temperatures. Fuel-consumption curves show fuel economy comparable with that of the normal engine.

MR. SPARROW'S paper emphasizes the importance of the question: “What is the minimum safe viscosity for an engine oil?” Although he does not attempt to solve the problem, he presents material “accumulated as a by-product of routine engine tests and development,” which, he says, indicates that rather low viscosities may be safe for bearings if and when we can be sure that the amount of lubricant which reaches the bearings will be adequate. He adds that it also indicates the extent to which safe lubrication of the cylinder bores depends upon the ability to produce and maintain smooth surfaces on pistons, piston-rings, and cylinder walls. He illustrates how a low viscosity is effective in increasing cranking speed and in reducing friction -thereby producing a gain in horsepower and fuel economy. He also cites examples to show the extent to which low viscosity is detrimental as regards oil consumption, blowby, and the protection which the oil film affords to the rubbing surfaces.

A TORQUE indicator, in which the reaction forces of the fixed gear in the propeller reduction gearing are measured, has been developed and flight-tested by Pratt & Whitney Aircraft Division of United Aircraft Corp. In this device the reaction forces are balanced by two hydraulic pistons, thus producing an oil pressure under these pistons which is proportional to the engine torque. The pressure of the oil, measured by an ordinary pressure gage in the cockpit, in conjunction with the engine speed and a suitable factor, gives the actual brake horsepower developed by the engine under all operating conditions of positive torque. Using a constant-speed propeller, it has been possible to make complete engine calibrations of power versus manifold pressures at various engine speeds at several altitudes between sea level and 20,000 ft.

BUS maintenance grew from haphazard patch-work repairs. Shortage of vehicles compelled stocking of service units. Standardization of equipment never has been accomplished. With competent mechanics not obtainable, they must be trained in bus work. Card files and other records now keep track of performance of every unit and all major parts. Service expectancy cannot always be based on the past performance of the part. Complete inspection of all parts is periodically necessary. Taxes make large numbers of standby buses economically impossible. High mileages are obtainable from modern buses. Rear engine locations are popular with the public. Larger and better oil and air filters are needed; the same is true of oil coolers. Lubrication is not a problem. All worn parts now pass through the salvage department. Most units on modern coaches are of ample size and cause little trouble. Hypoids operate satisfactorily. Fuel economy is quite satisfactory considering weights and operating conditions.

AIR transport operators desire primarily high reliability at lower fuel consumptions than are obtained at present. They look critically at the total economy picture, of which fuel economizing is but a part. If satisfactory schedule completion is possible at lower power at some optimum trip altitude, this method of economizing is highly desirable. Some decrease in specific consumption is possible with present grades of fuel, given improved mixture indicators or controls. Large improvements in specific consumption must be weighed economically against decreased reliability, increased maintenance, and increased fuel costs. Test-stand operation cannot be used directly to predict airline economy. Service experience is the only acceptable final test. The road to improved fuel economy is a long one with no safe short-cuts in sight.

THE increasing use of the analyses of the exhaust gas from an operating engine to measure air-fuel ratio has made the exact relation between composition and mixture ratio of some importance. Complete analyses of the exhaust gas are slow and laborious, and a simple relation between air-fuel ratio and one or more constituents easily determined by chemical analysis, or by automatic measurement of some property of the exhaust gas, is to be preferred, provided a suitable relation or calibration is available. The data in the literature are not altogether consistent. In the work reported in this paper, complete exhaust gas analyses for carbon dioxide, carbon monoxide, hydrogen, methane, and oxygen have been related to directly measured air-fuel ratios for three engines over a range of operating conditions and with varied air-measuring equipment.

DURING the past decade the general trend of aircraft-engine design has continued toward increased piston displacement, higher crankshaft speed, higher brake mean effective pressure, and improved materials. These changes have had a marked influence on increasing the overall performance of the airplane by improving take-off, bettering climb, permitting higher cruising speeds at greater altitude, increasing periods between overhaul, and improving the reliability of the powerplant. Although of secondary importance until quite recently, today fuel economy has become a major objective in both military and commercial operation. Fuel consumption is a function, generally speaking, of engine design, of the properties of the fuel itself, and of the procedure for introducing and regulating the fuel-air mixture in the operation of the powerplant.

THE need for improvement of fuel consumption in modern aircraft is stressed. The basic economy of oil engines for airline service is briefly summarized, together with the effect of lower fuel consumption on the range and payload of airplanes. The theoretical efficiencies of the Otto and Diesel cycles are compared with the efficiency actually obtained on present aircraft engines. The data are presented in condensed graphic form for easy comparison. A prediction is made of the fuel economy that may be expected from the gasoline aircraft-engine in the near future, together with a summary of the means required to obtain it. The prospective place of the compression-ignition engine in commercial and military service is briefly outlined. An analysis of the weight possibilities of compression-ignition engines as compared to present gasoline engines is made.

THE factors involved in cold starting of automobile engines, including the effects of temperature and oil viscosity on cranking speed and torque, have been known for many years. Many papers have been presented before the various Sections of the Society on these subjects. The S.A.E. crankcase-oil viscosity-numbers, which were adopted in July, 1926, provided for the classification of the lower-viscosity oils at 130 deg. fahr. and the higher-viscosity oils at 210 deg. fahr. It was recognized by 1930 that a classification for winter oils must be based on the viscosity of the oil at the starting temperature, and work was started on this problem. In June, 1933, the 10-W and 20-W oils, which are classified in accord with their viscosity at 0 deg. fahr., were adopted for publication and trial. The results of the use of these oils during the winter of 1933-1934, together with their advantages, are discussed.

THIS is Part 2 of a study of air resistance in terms that the automobile engineer can understand without delving deeply into aerodynamics. In Part 1, after analyzing car resistance mathematically, the author related how air resistance was determined by wind-tunnel tests of various body models and presented tabulated and charted results. A study of the test methods used is presented herewith, together with comparisons made between the results obtained in Part 1 and those obtained in Part 2 from road tests of a car equipped with a so-called “floating envelope.” Fuel consumption is considered also, since full advantage of streamlining cannot be obtained without improvement of the transmission to provide for sufficient activity of a car at the lower speeds. In conclusion, the salient facts of the entire paper are summarized and seven specific suggestions for streamlining are made to car builders.

THIS is Part 1 of a study of air resistance in terms that the automobile engineer can understand without delving deeply into aerodynamics. The study was suggested by the fact that motor-vehicles are now being driven at a speed at which most of the engine power is used to overcome air resistance, although the greater part of this resistance is unnecessary and can be eliminated by correct shaping of the vehicle body. It is a progress report of research just begun. After analyzing car resistance mathematically, the author relates how air resistance was determined by wind-tunnel tests of various body models. Numerous illustrations are utilized to portray the models and the testing equipment, and the data obtained are tabulated and charted.