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Diesel emissions are significant issue worldwide, and emissions requirements have become so tough that. the application of after-treatment systems is now indispensable in many countries To meet even more stringent future emissions requirements, it has become apparent that the improvement of market fuel quality is essential as well as the development in engine and exhaust after-treatment technology. Japan Clean Air Program II (JCAP II) is being conducted to assess the direction of future technologies through the evaluation of current automobile and fuel technologies and consequently to realize near zero emissions and carbon dioxide (CO2) emission reduction. In this program, effects of fuel properties on the performance of diesel engines and a vehicle equipped with two types of diesel NOx emission after-treatment devices, a Urea-SCR system and a NOx storage reduction (NSR) catalyst system, were examined.

In the Japan Clean Air Program II (JCAP II) Diesel WG, effects of fuel properties on the performance of two types of diesel NOx emission aftertreatment devices, a Urea-SCR system and a NOx storage reduction (NSR) catalyst system, were examined. For a Urea-SCR system, the NOx emission reduction performance with and without an oxidation catalyst installed in front of the SCR catalyst at low exhaust gas temperature operation was compared. For an NSR catalyst system, the effect of fuel sulfur on both emissions and fuel economy during 50,000 km driving was examined. Furthermore, effects of other fuel properties such as distillation on exhaust emissions were investigated. The results show that sulfur is the influential factor for both devices. Namely, high NOx emission reduction performance of the Urea-SCR system with the oxidation catalyst at low exhaust gas temperature operation is influenced by sulfur.

Combustion chamber deposits (CCD) in wall-guided stratified charged direct injection spark ignition (DISI) engines affect combustion significantly because CCD may disturb the air-fuel mixture formation and, as a result, cause emission deterioration. For the design of engines and fuels, it is therefore important to determine the effects of CCD on emissions from DISI engines. In this study, the effects of CCD on emissions from a DISI engine using different fuel distillation properties were investigated. The study results show that, during stratified charged operation, an increase in CCD increased the total hydrocarbon (THC) emissions under high speed conditions and the NOx emissions under the low speed conditions.

The effects of gasoline fuel properties on exhaust emissions were investigated. Port injection LEVs, a ULEV, a prototype SULEV which were equipped with three–way (3–way) catalysts and also two vehicles with direct injection spark ignition (DISI) engines equipped with NOx storage reduction (NSR) catalysts were tested. Fuel sulfur showed a large effect on exhaust emissions in all the systems. In the case of the DISI engine with the NSR catalyst, NOx conversion efficiency and also regeneration from sulfur poisoning were dramatically improved by reducing sulfur from 30ppm to 8ppm. Distillation properties also affected the HC emissions significantly. The HC emissions increased in both the LEV and the ULEV with a driveability index (DI) higher than about 1150 (deg.F). The ULEV was more sensitive than the LEV. These results show that fuel properties will be important for future technologies required to meet stringent emission regulations.

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.

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.