Fig. 2.—Distillation curves of motor fuel sold in Detroit, Mich., from 1916 to 1919. The data for each curve are as follows:—
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Curve No. 9 10
Fuel Petrol Petrol Petrol Petrol Petrol Petrol Petrol Alcohol Cal. Dist. Paraffin
Date of Purchase
4/5/16 7/10/16 9/11/16
6/9/17 1/24/19
4/30/19
6/18/19
10/18
18
18
Baum6 60-5
57-5 56-8 56-8 57-3 55-7 55-o 42-2
5i-4 40-0
there is very little resistance to the passage of the combustible mixture past it, and very little then flows through the by-pass or heating jacket; on the other hand when the throttle is nearly closed the passage through it offers much more resistance, and a much greater proportion of the fuel charge passes through the heating jacket, which is in accordance with the requirements.
In early cars the fuel tank was almost invariably located in the front seat, and the fuel was fed by gravity to the carburetter. Later the bodies were constantly lowered, partly to secure greater stability and partly for the sake of appearance, and at the same time the carburetter had to be raised in relation to the engine, owing to the lessened volatility of the fuel. The result was that sometimes when the car had to ascend a steep grade and there was little fuel in the tank there was no head on the fuel, and none would flow to the carburetter. Some of the earlier high-class cars were provided with a pres Spark Plug
sure fuel feed system, by which gas under pressure, taken through an " adapter " from the engine cylinders, was made use of to force petrol from a tank carried on the frame at the rear to the carburetter. There were two major objections to this system of feed: carbon particles from the engine cylinder often got into the fuel tank (in spite of the gas being passed through a fine- mesh wire-gauze strainer) and thence into the carburetter jet, which sometimes became clogged; besides, every time the fuel tank was filled the compressed gas escaped, and to get an initial flow it was necessary to obtain pressure by a hand air-pump. By placing the fuel tank under the cowl instead of in the front seat sufficient head for gravity feed was generallyobtainable, but the cowl tank usually had an awkward shape and was of rather small capacity. The solution was found in the vacuum feed system, which was developed by the Stewart-Warner Speedometer Corp., Chicago. By this system (fig. 4) the suction or vacuum in the inlet pipe of the engine was made use of for transferring the fuel from a rear tank to an auxiliary tank mounted on the forward side of the dashboard, as high as possible. The auxiliary tank had two compartments, an upper and a lower. Into the upper compartment the fuel was drawn by the vacuum, and it was periodically transferred to the lower by a float valve. Thence it flowed to the carburetter by gravity. There was always sufficient fuel in the carburetter float chamber and in the auxiliary tank to start the engine after the main tank had been refilled.
In 1910 ignition on practically all motor-cars was by high-tension magneto. In 1920 nearly all American makes of passenger car had battery and coil ignition. French manufacturers were also adopting battery ignition, while British manufacturers with few exceptions adhered to the magneto. The reason for the change from magneto to battery ignition was that all passenger cars in 1920 were equipped with a generator and storage battery; consequently there was a constant and plentiful supply of current available, and there was no need for an additional current generator in the form of a magneto. As compared with the early coil and battery systems, the only differences consisted in the use of a plain coil instead of a vibrator coil and of a mechanical interrupter instead of a timer. Sometimes safety devices were provided for automatically opening the circuit or reducing the current flow if the operator should forget to open the switch when the motor stalled. No fundamental changes were made in the cooling system with the exception of the introduction of the thermostat for the control of the circulation. This instrument is connected in the cooling circuit in such a manner that it prevents circulation through the cylinder jackets until the latter have attained a certain predetermined temperature, generally about 170 F. The result is that in starting from cold the engine reaches its normal working temperature in much shorter time, and trouble due to incomplete vaporization of fuel is reduced. The thermostat used, known as the Sylphon, consists of a corrugated copper cylinder filled with a liquid which vaporizes at the temperature at which the thermostat is to act (fig. 5). Many passenger-car radiators are fitted with a radiator thermometer in the filler cap, which is a help to the operator in trying to keep his engine running at its best temperature and gives an early indication of incipient overheating.
Fig. 3.—Cross section of Fuelizer on Packard "Twin-Six" engine.
