Drivability tests were conducted on 12 cars at four ambient temperatures with seven fuels of differing front-end and mid-boiling range volatility levels. One fuel was a typical winter grade gasoline, one was typical of summer grade, and the remaining five were blended to provide various combinations of Rvp and ASTM 50% evaporation temperature. Three driving schedules were used on the chassis dynamometer-a cold-start driveaway schedule to study operation from cold start through warmup, a warm-vehicle procedure to evaluate drivability with a thoroughly warmed-up car, and a hot-start vapor lock procedure to observe hot-fuel handling characteristics.
Road tests were run at one temperature on four cars with two fuels for correlation between road and dynamometer results. For additional correlation between road and dynamometer, the dynamometer results at one temperature were compared to the results of road drivability tests conducted by CRC at Pasco, Wash. in 1969, which used four of the same fuels.
The results of this program showed that the drivability characteristics of automobiles and their sensitivity to changes in physical properties of fuels can be evaluated on a chassis dynamometer. In general, the chassis dynamometer is more discriminating or more severe than comparable road tests. Correlations are developed showing the response in terms of drivability to changes in fuel properties.