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The effects of diesel fuel properties (aromatic content, cetane index and T90), cetane improver, oxygenates, high boiling point hydrocarbons and aromatics distribution on diesel exhaust emissions were studied under the Japanese 10-15 test cycle and the ECE+EUDC test cycle. The test vehicle was a TOYOTA COROLLA with a natural aspirated, 2.0L displacement, IDI diesel engine. It was demonstrated that particulate emissions are highly correlated with T90 and that NOx is affected by the aromatic content of fuel. A reduction in particulates emissions was observed in fuel with a lower cetane number by adding cetane improver, but this reduction was limited. Cetane improver had no effect on NOx emissions in the 45 # 60 cetane number range. Oxygenates reduced particulate emissions remarkably but had little effect on NOx emissions. A decrease in the soot in particulates was particularly observed.

The 50% and 90% distillation temperature (T50 & T90), aromatics, olefins and sulfur content are regulated in California Phase2 Reformulated Gasoline. The effects of these properties on the exhaust emissions were investigated. Twelve test fuels with little interaction between T50, T90, aromatics and olefins were prepared. Exhaust emissions were measured using a TLEV according to 1975 Federal Test Procedure (75 FTP). T50 had a large effect on exhaust HC emissions. T90 also affected HC emissions. Both increasing and decreasing T50, T90 showed increasing exhaust HC emissions. These results suggest that an optimum range of T50 and T90 exist for lowering exhaust HC emissions. The effects of sulfur on exhaust emissions were also investigated. A Pt/Rh type catalyst (production type) and a Pd type catalyst (prototype) were prepared. These catalysts were put on a 94MY TLEV. Increase of sulfur lead to increase of the exhaust emissions with both catalysts.

According to the principle of pH measurement, an on-board type engine oil deterioration sensor has been developed. The developed sensor is composed of a Pb and oxidized stainless steel electrodes. The sensor signal shows a good linear relationship to the quasi-pH value of the oil. Especially in the region where the oil deterioration proceeds, the remaining basic additives in the oil is easily estimated from the sensor signal.

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.

Fifty percent distillation temperature (T50) can be used as a warm-up driveability indicator for a hydrocarbon-type gasoline. MTBE-blended gasoline, however, provides poorer driveability than a hydrocarbon-type gasoline with the same T50. The purposes of this paper are to examine the reason for poor engine driveability caused by MTBE-blended gasolines, and to propose a new driveability indicator for gasolines including MTBE-blended gasolines. The static and dynamic evaporation characteristics of MTBE-blended gasolines such as the evaporation rate and the behavior of each component during evaporation were analyzed mainly by using Gas Chromatography/Mass Spectrometry. The results of the analysis show that the MTBE concentration in the vapor, evaporated at ambient temperature (e.g. 24°C), is higher than that in the original gasoline. Accordingly, the fuel vapor with enriched MTBE flows into the combustion chamber of an engine just after the throttle valve is opened.