New Approach to Evaluation of Fuel Volatility and Associated Engine Variables

THE test procedure presented here is a new approach to the evaluation of engine warmup as influenced by fuel volatility. The procedure developed is an attempt to express driver feel on a sound technical basis. Data are included that indicate good correlation of test results with customer reaction.

The wide variation in warmup performance of postwar passenger cars and their sensitivity to volatility and ambient temperature is illustrated by several examples. It was found that manifold cleanliness and manifold heat were most important of the engine and operating variables evaluated.

Tests showed that the 50% point had the greatest bearing on the warmup ability of fuels and indicated that the 10 and 90% points influenced the initial and final warmup, respectively.