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An emissions programme has been undertaken to gain information on the effect of selected fuel parameters on gasoline direct injection (G-DI) vehicle technology(1) with respect to exhaust emissions. Seven fuel parameters, namely aromatic, methyl-tertiary-butyl ether (MTBE), sulphur and olefin content as well as 3 distillation parameters covering the whole boiling range, were independently investigated. It was found that, overall, the fuel effects on regulated (THC, CO, NOx), particulate (Pm), and CO2 emissions were relatively small.

The influence of the molecular structure of hydrocarbon fuels on soot, SOF, and NOx emissions from a diesel engine was analyzed while ignition delay and other physical fuel properties were kept constant. Mixtures of normal paraffin (n-tetradecane) and iso-paraffin (heptamethylnonane) were used as a base fuel and one of 5 kinds of hydrocarbons including mono-aromatic, di-aromatic, and non-aromatic was added. The aromatic content varied in the range of 0-60 vol % for the mono-aromatic fuels and 0-40 vol % for the di-aromatic fuels. The experimental results showed that regardless of the molecular structure of the fuel, both particulate and NOx emissions increased linearly with the C/H atomic ratio of the fuels under constant ignition lag. The increase in particulate emissions with C/H atomic ratio was caused by increases in dry soot. The SOF, THC, and BSEC were little affected by the C/H atomic ratio and molecular structure of the fuels.