In response to various reformulated gasoline regulations, several studies have been conducted to evaluate the relationship between fuel properties and vehicle exhaust emissions. These studies, however, have focused on the fuel effect and have not examined the most promising advanced technology emission control systems on low emission vehicles.
Toyota's reformulated gasoline research first set out to study the effect fuel compositions has on 2 different emission control systems. On both systems, non-methane hydrocarbon (NMHC) emissions were significantly affected by the 50% and 90% distillation temperature (T50 and T90). A correlation was also found exhaust olefine content and the amount of MTBE contained in the fuel.
Research was also conducted on the specific ozone reactivity (SOR) of exhaust hydrocarbons. Various fuels with similar specifications but blended from different feedstocks were evaluated. Test result indicate that as fuels ozone forming potential increases, that exhaust specific ozone reactivity also increases.
A third testing phase studied the effect of fuel sulfur content on exhaust emissions and catalyst performance. FTP emission tests and engine bench tests were carried out using gasoline with sulfur contents ranging from 2 parts per million (ppm) to 300 PPM. It was found that the fuel sulfur content significantly affects NMHC, carbon mono-oxide (CO), and oxides of nitrogen (NOx) emissions. Bench tests also indicate that increased fuel sulfur levels lower catalyst efficiency. Catalyst performance, however, improved after approximately ten minutes of driving a vehicle fueled with low sulfur (2ppm) gasoline at an engine-out temperature of 700 °C. The test results indicate that fuel sulfur has temporary and reversible effect on catalyst efficiency.
These results show that ARB Phase 2 reformulated gasoline is effective in reducing exhaust emissions.