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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.

Onboard refueling control technology has been successfully applied to two vehicles with 98+% efficiency in tests with 10.5 RVP fuel at 84° F. The Onboard system, which controls exhaust, evaporative, refueling, and so called “running losses”, was constructed out of components found in current automotive evaporative control systems. During refueling, the tank vapors are forced into the enhanced charcoal canister by a flowing liquid seal in the fillpipe. The canister was removed from the engine compartment and mounted within the vehicle frame close to the fuel tank. Each vehicle demonstrates a different possible safe location from a crash worthiness viewpoint. In order to further improve safety by preventing the expulsion of liquid gasoline upon gas cap removal, the orifices in the production tank vent lines were removed so that the fuel tank is at atmospheric pressure at all times. As modified, no significant driveability differences from production vehicles were found.

Onboard refueling control technology has been successfully applied to two vehicles with 98+% efficiency without a vapor seal in tests with 11.8 RVP fuel at 88°F. The elements of the onboard system were constructed out of components similar to those found in current automotive evaporative control systems. The entire system was designed for minimum pressure drop so that a mechanical or liquid seal is not necessary. The flow of fuel into the tank provides enough pressure to force the tank vapors into the canister. Control of evaporative emissions was improved to the extent that the 2 grams/test standard for a 9 RVP fuel was met with a fuel of 11.8 RVP. Effects on tailpipe emissions, and canister size are also discussed.