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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 properties of diesel fuels were investigated in terms of particulate emissions to clarify the specification of such a diesel fuel for minimizing particulate emissions. Diesel fuels were analyzed using thin layer chromatography (TLC), and gas chromatography/mass spectrometry (GC/MS). These analysis revealed the entire composition of hydrocarbons in diesel fuels according to molecular formula. The entire composition of hydrocarbons in diesel fuels could be expressd on a three-dimensional graph: the X-axis as carbon number, the Y-axis as H/C ratio and the Z-axis as the amount of hydrocarbons of identical molecular formula. By using the graph, the properties reported so far were investigated. Also, simplified images of the fuel sprayed into a cylinder and its flame were derived from the observational results previously reported.

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.

An investigation of throttle response of engines during warm-up was conducted using various gasolines. Test data were obtained from an engine on a test bench at intermediate temperature around 20∼ 30 °C. By using the engine test bench data, correlation coefficients between engine response time and gasoline characteristics were calculated. The result shows that the middle range of distillation temperature is an important factor in gasoline characteristics for warm-up driveability of fuel injected engines. It also shows that 50% distillation temperature can be used as one indication of warm-up driveability. This indication is effective only for hydrocarbon type gasolines. In the case of MTBE blended gasoline, the distillation temperature becomes low when MTBE is blended to gasoline, but throttle response was not improved. It is also found that the effect of gasoline distillation on throttle response is enhanced by intake valve deposits.