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A vehicle emissions test program was conducted to evaluate the impact of gasoline RVP reduction on CO emissions under conditions that are typical of CO exceedance days in Las Vegas and Los Angeles. Test results showed that CO emissions were reduced in the Las Vegas fleet when RVP was changed from 12 to 9 psi. In the Los Angeles fleet, the results were less consistent, perhaps due to the poorer integrity of evaporative emissions control systems on these vehicles. This suggests that an optimum emissions control strategy might include both RVP reduction and an effective vehicle inspection and maintenance (I&M) program.

Two fleets of thirty vehicles each were emissions tested in order to determine the effect of gasoline RVP reduction on tailpipe carbon monoxide (CO) emissions in Las Vegas and Los Angeles under conditions typical of winter CO exceedances in these two cities. The hypothesized emission reduction was confirmed for Las Vegas. However, for Los Angeles, the effect of RVP was questionable. The reason or reasons for this discrepancy between the two cities could not be completely resolved from this study. Detrimental emissions effects of reduced RVP under cold temperatures were found to be small and inconsequential.

An auxiliary fueled prechamber ignition system can be used in an IC engine environment to provide lean limit extension with minimal cyclic variability and low emissions. Geometry and distribution of the prechamber orifices form an important criterion for performance of these systems since they are responsible for transferring and distributing the ignition energy into the main chamber charge. Combustion performance of nozzles with a single jet, dual diverging jets and dual converging jets for a methane fueled prechamber ignition system is evaluated and compared in a rapid compression machine (RCM). Upon entering the main chamber, the dual diverging jets penetrate the main chamber in opposite directions creating two jet tips, while the dual converging jets, after exiting the orifices, converge into a single location within the main chamber. Both these configurations minimize jet-wall impingement compared to the single jet.