PREVIOUS work on vapor lock at the Bureau of Standards under the auspices of the Cooperative Fuel Research Steering Committee has resulted in considerable information regarding the relation between the properties of gasolines and vapor lock and between fuel-line design and vapor lock. Satisfactory means have been developed for predicting the conditions under which vapor lock would occur with a given fuel, but no extensive information has been available on the gasoline temperatures existing in the fuel feed lines of automotive equipment. This has made it very difficult for the refiner to supply satisfactory fuels for current automotive equipment.
The present report includes temperature data obtained at several points in the fuel feed systems of 27 automobiles and 8 buses under various operating conditions. At 40 m.p.h., the maximum temperature observed in the fuel systems of the passenger-cars studied was 73 deg. fahr. above atmospheric temperature, while the average temperature at the fuel-pump or vacuum-tank outlet for the 27 cars was 41 deg. above that of the atmosphere. During idling after a 40-m.p.h. run, the temperature increased still further by as much as 20 deg. The fuel-line temperatures found in the buses investigated were, on the average, slightly lower than those found in the passenger-cars.
The results obtained reflect seriously on the design of automobile fuel-feed systems, and certain suggestions are made regarding improvement in design on the basis of the experimental data. It is considered that the introduction of fuel-pumps has been more responsible for the widespread occurrence of vapor lock than has any increase in the average volatility of fuels during the last two years, and therefore it behooves the automotive engineer to do his part in keeping the fuel system as cool as possible. With some care and thought on the part of the designer, it is felt that the gasoline temperature at the fuel-pump can be materially reduced.