Search Results

Blends of up to 20% methanol in gasoline were evaluated in both engine dynamometer and controlled vehicle tests, and in a 50,000 mile road test. Performance comparisons between methanol blends and base gasolines were made in vehicle driveability and vapor lock tendency, engine deposits and wear, fuel economy, exhaust emissions, compatibility with fuel system materials, and phase stability of the blends. Vapor lock tests in six 1974 cars strongly suggested that the vapor lock tendency of methanol blends is greater than would be predicted for gasolines having the same volatility characteristics. Cold start and warm-up driveability of two 1974 cars at 70°F depreciated as methanol concentration increased in base fuels of three volatility levels. These driveability data were found to correlate well, at a given methanol concentration, with fuel volatility characteristics described by means of a new fuel vaporization pressure technique.

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.

Annually, the Coordinating Research Council (CRC) sponsors a nationwide survey of octane number requirements for current model passenger cars. In this review, based on surveys from 1965 through 1974, trends in octane number requirements reflect changes in engine design and exhaust systems to meet the legislated limits on emissions. The average requirement dropped approximately 5.5 Research octane numbers over the ten-year period with the most dramatic drop of approximately 3.0 octane numbers in 1971 when car manufacturers recommended use of 91 octane gasoline. The trends toward lower average requirements since 1971 have been determined with both leaded and unleaded fuels. Incidence of surface ignition knock and rumble was about one per cent in 1965 and tended to disappear after 1971. The average spread of octane number requirements between 10 and 90 per cent of cars satisfied increased about 2.5 numbers over the period.