Search Results

Results from two separate emission test programs using a fifteen fuel test matrix in which ten key fuel properties were independently varied have shown that changes in gasoline distillation characteristics, olefin content and Reid vapor pressure (RVP) can produce major changes in total tailpipe exhaust emissions. All other variables examined, including oxygen content and aromatic content of the fuels, did not directly affect the tailpipe output of carbon monoxide, nitrogen oxides, or hydrocarbon emissions. From these results a generalized mathematical model was produced which predicts tailpipe emission changes from key fuel properties. The model was verified in a separate, 13 vehicle study.

The five noncyclic hexane homologs were mixed and tested for their octane qualities. The mixtures of normal hexane with the branched homologs, as well as a few of the combinations of branched species, had statistically significant higher octane quality than would be expected if the compounds responded in the CFR octane test engines as a linear combination of the individual components. It is hypothesized that this positive interaction is a reflection, of the formation of intermediates, via intermolecular hydrogen abstraction reactions, which are not able to progress along branching pathways during the combustion process. The formation of these intermediates delays the low temperature reaction kinetics, making the reaction mixture more knock resistant than expected.