A Correlation Between Tailpipe Hydrocarbon Emissions and Driveability

Simultaneous tests of emissions and driveability conducted at 4.4°C on a chassis dynamometer using 10 late model vehicles showed a strong correlation between degraded driveability and increased tailpipe hydrocarbon emissions. Other regulated emissions were uncorrelated to driveability, or were small in magnitude. The 24 test gasolines were systematically varied in front-end, mid-range, and tail-end volatility and so spanned much of the moderate and high DI (driveability index) fuel region. Splash blends of 10%.vol ethanol and 15%_vol MTBE blended gasolines were tested in addition to hydrocarbon gasolines.