AUTOMOBILE ENGINE. Historically and mechanically the automobile engine is de rived from the stationary and marine gasoline engines developed before 1890. (See INTER NAL COMBUSTION ENGINE; GASOLINE ENGINE). These were either 4-cycle or 2-cycle engines, and automobile engines were developed on both plans, though very unequally. Gottlieb Daim ler and Karl Benz selected the 4-cycle type for the small and experimental vehicles built by them in 1884, 1885 and 1886, from which the first automobile constructors in France received their inspirations, and when France soon after ward took a decided lead in production and design the 2-cycle engine was neglected by the majority of engineers in the matter of develop ing it for vehicle work. It continued in favor for small motor boats in England and America, received the benefits of the rapid improvements in materials and production methods extending to all classes of hydrocarbon engines, and every now and then it has been taken up for use in automobiles. But in nearly every instance of this sort it was eventually abandoned again, falling behind the 4-cycle type, to whose im provement by far the larger resources were devoted. The common prototype of the class of engine primarily to be considered is thus the single-cylinder, 4-cycle engine described and illustrated under GASOLINE ENGINE, STA TIONARY. By taking note of the deficiencies for vehicle work which cropped out from the moment it was applied for this new purpose and by following the efforts made for remov ing these shortcomings, one arrives at length to any and all of the types now in use, each type representing originally some variation in judgment with regard to the relative import ance of different requirements or the means for meeting them. In the prototype of auto mobile engines the following shortcomings were immediately apparent: The great weight, due to thick castings, large flywheel, large water tank and water supply. Violent shaking and vibration, due to single-cylinder design and un balanced mass of piston, connecting-rod and crankarms and crankpin of the engine shaft. Failure to operate at more than one speed, due ings, wrong composition and weak compression of the explosive charges, overheating, failing lubrication. Small and irregular power develop
ment, due to overheating, low maximum speed, small valve ports and gas conduits, poor com position of fuel mixture. Noise and odor of ex haust, due to single-cylinder design, incomplete combustion of explosive mixture and unsuitable mufflers. Noise of engine and cam gears, due to unbalanced mass of rotating and reciprocat ing parts, poor design and cut of the gears.
As the construction having these faults rep resented the best knowledge of its day, it could be improved only by degrees, in the measure as knowledge grew among designers and skill and production facilities were developed in the industries supplying new materials and machin ery. When one fault was alleviated another one was often aggravated by the remedy. Sav ing weight by using a smaller flywheel, for example, made shaking and vibrations worse and starting of the engine more laborious and uncertain. Reduction of the water supply made overheating—with dwindling of power and seiz ure of pistons—for a long period a most corn mon trouble, and while radiators were at once devised to take care of excess heat the im provements in carburetors and ignition, result ing in more power and higher speed kept the generation of surplus heat ahead of the radia tor improvements and other improvements for checking it. In more recent days, larger valve ports and lengthened piston stroke doubled and trebled the engine speed and power that could be obtained from a cylinder of a given bore, but resulted also in the return of vibration and difficulties in effecting ignition and lubrication rapidly enough, and these reverting troubles had to be remedied in turn by further lighten ing and finer balancing of reciprocating parts as well as by subtle changes in valve and cam shapes and settings, so as to get combustion started and finished to best advantage, before a practical gain in engine values could be re alized from the increased speed and power. To be able to operate this improved engine slowly and with small fuel charges as well as rapidly and with full charges is still an object to be realized in the same degree that was attained in the heavier, larger and slower engines which preceded them in the evolution.