The author states that considerable thought has been devoted recently to the relation of fuel end-point to fuel economy. It has been shown that, provided an intimate mixture of fuel-vapor and air is secured, such a mixture will not condense at the ordinary temperatures of the intake. However, on the contrary, crankcase dilution, an excess of deposited carbon, low mileage per gallon of fuel and ignition trouble are being experienced. There appears to be a discrepancy between the efficiency that should be attained and what is actually attained. To investigate this the Bureau of Standards undertook a brief series of experiments to rough out a line of procedure.
Regarding compression of a dry mixture, curves are shown to illustrate that gasoline vapor compresses when “dry.” Detonation was evident when using one spark-plug and there was no detonation when using two spark-plugs. After preliminary experiments of the nature already indicated, a pressure indicator was used, at pressures just on the verge of detonation, to find the exact point where detonation occurs. Charts are exhibited to show the location of the piston with reference to its center position, with one spark-plug and with two spark-plugs; and the effect of spark-advance on the maximum explosion pressure and brake-horsepower, using one spark-plug. An explanation which goes into considerable detail supplements the charts.