How Heavy Hydrocarbons in the Fuel Affect Exhaust Mass Emissions: Correlation of Fuel, Engine-Out, and Tailpipe Speciation — The Auto/Oil Air Quality Improvement Research Program

Species analyses have been performed on engine-out and tailpipe hydrocarbon mass emissions to help understand why fuels with increasing amounts of heavy hydrocarbon constituents produce significantly higher tailpipe hydrocarbon emissions. Mass and speciated hydrocarbon emissions were acquired for a fleet of ten 1989 model year vehicles operating on twenty-six fuels of differing heavy hydrocarbon composition. These fuels formed two statistically designed matrices: one examining the effects of medium, heavy, and tail reformate and medium and heavy catalytically cracked components; and the other examining the effects of heavy paraffinic versus heavy aromatic components and the effects of the 50% distillation temperature.

In this paper the fates of fuel species were traced across the engine and across the catalyst, and correlations were developed between engine-out and tailpipe hydrocarbon species emissions and fuel composition. Engine-out and tailpipe specific ozone reactivities were examined in light of the engine-out and tailpipe speciation, and correlations were developed between these specific reactivities and fuel composition.