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Effects of fuel properties, in terms of the 90% boiling point (T90) and the polycyclic aromatic hydrocarbon (PAH) content, as well as oxidation catalysts on diesel exhaust emissions have been examined using three direct injection (DI) diesel engines and two diesel passenger cars equipped with oxidation catalysts. The diesel emission tests using two series of test fuels, one for examining the effects of the T90 and another for polycyclic aromatic hydrocarbons, have indicated that total hydrocarbons (THC) and particulate matter (PM) decrease as the T90 is reduced. PM and THC were also found to be on a declining trend with a decreasing content of polycyclic aromatic hydrocarbons. The extent of these effects of fuel properties on exhaust emissions varied with engine and car models, and appeared to be smaller in engines or cars having lower exhaust emissions.

We conducted a study of the effects of engine technology and fuel properties on diesel exhaust gas emissions. The effect of fuel properties on exhaust gas emissions was examined using four D.I. diesel engines equipped with an oxidation catalyst, high-pressure injection, turbocharger and natural aspiration fuel charging. In addition, oxidation catalysts were installed on the two turbocharged (T/C) and natural aspirated (N/A) engines to examine their effects on reducing exhaust emissions. As a result, it was found that the installation of oxidation catalyst clearly had an effect on reducing the levels of hydrocarbons (THC), carbon monoxide (CO) and particulate matter (PM). The high-pressure injection engine was found to have a low level of PM and not be affected by the type of fuel. It was clearly shown that engine technology has a greater effect on reducing exhaust emissions than fuel properties.