The influence of gasoline formulation on combustion and emissions in spark-ignition engines

Regulated and some unregulated emissions of a medium size not catalyst vehicle obtained with different formulations of unleaded fuels have been measured. Among the unregulated pollutants, 1-3 butadiene, benzene, toluene, and polycyclic aromatic hydrocarbons (PAH) have been considered because of their toxicological hazards. The emission levels have been compared with the ones obtained in similar conditions using a leaded reference fuel. Cold start Europe cycle and two not standard cycles have been used as basis of comparison for pollutants measurement. The effect of a three way catalytic system, fitted on the same vehicle, on regulated and unregulated has been also studied, evaluating the conversion efficiency for the different pollutants. The same fuels have been tested in the same driving conditions on a small size passenger car too, equipped by factory with catalyst and closed loop control system. It has been shown that benzene and toluene content in the exhaust depends on their original concentration in the fuel. The performance of catalytic after-treatment system is satisfactory even if no closed loop control is provided. Driving conditions play a fundamental role on regulated and unregulated emissions independently of the presence of an exhaust treatment device.