Technical Paper
Weather or Knock Road Ratings and Requirements, Year-Round
1954-01-01
540247
SEVERAL factors are involved in the answer to the question, “How do atmospheric conditions affect the ability of a fuel to satisfy the antiknock requirement of automotive engines?” As is well known, an increase in atmospheric temperature increases the octane-number requirement of engines. This paper points out, however, that this causes little change in the road octane-number ratings of commercial fuels. Increasing the absolute humidity has the opposite effect to increasing the temperature and tends to counteract the undesirable effects of changing temperature throughout the various seasons of the year. Increasing the barometric pressure or decreasing the wind velocity both increase the tendency of commercial fuels to knock. Factors indirectly related to weather conditions, such as the coolant or thermostat used in an engine, also affect the knocking tendency of a fuel.