EUEAL ENGINEERING. 689 



Preheating of the charge, also, is necessary in cold weather, and the heavier 

 distillates require hi;:lior compression and earlier ignition than gasoline in order 

 to give the best results. The water feed is the most important factor. . . . 

 Gasoline engines already in service can be altered by replacing the fuel mixer 

 and the exhaust block with specially designed ones, or by adding a homemade 

 device for feeding water into the air inlet pipe. . . . The effects of the water 

 in the charge are softened explosions, more complete combustion of the fuel, a 

 cleaner cylinder, cleaner valves, uniform temperature with reduced loss of 

 power in the jacket water, and no preignition. Despite the loss of power in the 

 heat of vaporization of the feed water, the fuel economy of the engine is not 

 lowered. 



" Two-cycle engines with hot-ball ignition and fuel injection at the end of 

 the compression stroke can be operated on low gravity distillate, even down to 

 30° Baumg for small engines, and to 24° Baum6 for large engines, provided the 

 compression pressure is increased to 180 lbs. per square inch. As in the case of 

 4-cycle engines, water feed is essential except perhaps when the engine is car- 

 rying less than one-third of its full load. . . . Forced-feed lubrication is nec- 

 essary for hot-ball engines and is desirable for large 4-cycle engines. Pump 

 circulation gives much better results than the thermosiphon system for hot-ball 

 engines. 



" Fuel economy of 9 or 10 brake horsepower-hours per gallon of fuel oil is 

 possible with farm engines of either type, assuming the engine to be in good 

 condition. In the average ranch pumping plant the fuel economy is about 6 or 

 7 horsepower-hours per gallon. The determining factor of fuel economy is the 

 adjustment of the fuel valves. . . . Nearly all oil engines are operated with 

 the fuel valves opened wider than is necessary. . . . Mechanical losses of 

 power in an engine are most important when the engine is only partly loaded. 

 An engine should be run at from three-quarters to full load. A purchaser should 

 compute his power requirements carefully and then add about 15 per cent to 

 determine the size to buy. At altitudes of from 3,000 to 5,000 ft. from 25 to 30 

 per cent should be added to the computed capacity. . . . The piston displace- 

 ment per minute per horsepower is the best indication of the capacity of an 

 engine. . . . The quantity of humidifying water should be controlled by the 

 governor. ... 



" Four-cycle oil engines with electric ignition are proving to be quite as re- 

 liable as gasoline engines. The combustion of the fuel oil is perfect and there 

 is no exhaust smoke. The explosions can be timed perfectly and they occur 

 with great regularity. Compared with gasoline, the only disadvantage in burn- 

 ing tops is with respect to starting in cold weather, when it is necessary to run 

 for from one to five minutes on gasoline and then change over to tops. 



" The experience had with hot-ball engines in Arizona to date has been unsat- 

 isfactory. The combustion is imperfect, usually bad. Hot-ball ignition has 

 serious disadvantages. The evil effects of leaky compression are very great. 

 Pump lubricators, water-circulating pumps, and friction-clutch pulleys are 

 required even on small engines. On careful analysis the hot-ball engines do not 

 have any advantage in simplicity. Their useful life will be less than that of 

 4-cycle engines. . . . 



" The use of tops in place of engine distillate decreases the cost of pumping 

 from 20 to 40 per cent. The cost of pumping on a 40-ft. lift with 4 ft. depth 

 of application varies from $8 to $20 per acre, according to whether the plant 

 is used much or little. Under the most favorable conditions the cost of pumped 

 water is no greater than the cost of river water. The cost of pumping on a 

 100-ft. lift with 4 ft. depth of application varies from ?20 to $40 per acre. 



