A New CRC Cold-Start and Warm-Up Driveability Test and Associated Demerit Weighting Procedure for MPFI Vehicles

The Coordinating Research Council (CRC) volatility group has issued a new cold-start and warm-up driveability test designed to improve the resolution of volatility effects on MPFI vehicles. Additionally a new demerit weighting procedure is now available to use with the new test. The weighting procedure was developed through an intermediate-temperature cold-start and warm-up driveability program conducted in the fall of 1994. The program also evaluated the effects of MTBE and volatility (driveability index) in late-model vehicles. The new test procedure and demerit calculation ordered fuels by volatility and generally generated higher average demerit levels for MPFI vehicles than the procedure used in previous cold-start programs. As in previous programs, driveability was a nonlinear function of DI and the presence of MTBE was not found to be a statistically significant effect. A volatility index based on percent evaporated was generated. The coefficients for E200 and E300 were roughly equal.