COLD WEATHER DRIVEABILITY PERFORMANCE OF LATE MODEL CARS

Driveability performance of recent model cars has been adversely affected by design requirements for lowering exhaust gas emissions. Published reports have indicated a need for gasoline volatility modifications to minimize the impact of these engine design changes on driveability. This paper presents the results of a low-temperature program to investigate the driveability performance of ten 1973 U.S. vehicles and to determine the effect on performance of changes in gasoline volatility.

Driveability performance was affected much more by engine design variables Chan by changes in fuel volatility. In Cold Start and Driveaway operation-, some cars performed well on all fuels at all temperatures. Others gave poor performance on most fuels at all temperatures--with hesitation, stumble, stall on acceleration and stall immediately after start-up being most prevalent problems. During Warm Operation, the primary malfunction noted was surge which varied widely among the ten cars tested and was unrelated to fuel volatility. In several cars, Warm Operation problems approached or exceeded those found in Cold Start and Driveaway operation.