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This work was concerned with evaluation of the performance and emissions of potential future biofuels during advanced spark ignition engine operation. The fuels prepared included three variants of gasoline, three gasoline-ethanol blends and a gasoline-butanol fuel altogether covering a range of oxygen mass concentrations and octane numbers to identify key influencing parameters. The combustion of the fuels was evaluated in a turbocharged multi-cylinder direct fuel injection research engine equipped with a standard three-way catalyst and an external EGR circuit that allowed use of either cooled or non-cooled EGR. The engine operating effects studied at both part and boosted high load conditions included fuel injection timing and pressure, excess air tolerance, EGR tolerance and spark retard limits. A number of blends were also mapped at suitable sites across the European drive cycle under downsized engine conditions.

The work was concerned with applying cooled EGR for improved high load fuel economy and reduced pollutant emissions in a turbocharged gasoline engine. While the thermodynamic benefits of EGR were clear, challenges remain to bring the technique to market. A comparison of pre and post compressor EGR supply indicated that post-compressor routing allowed higher compressor efficiencies to be maintained and hence reduced compressor work as the mass flow of EGR was increased. However, with this post-compressor routing, attaining sufficient EGR rate was not possible over the required operating map. Furthermore, at higher engine speeds where the pre-turbine exhaust pressure was greater than the intake plenum pressure, the timing of peak in-cylinder pressure was not as readily advanced towards the optimum.

Gasoline engine downsizing is one of the main technologies being used to reduce automotive fleet CO₂ emissions. However, the shift in operating point to higher loads which goes with aggressive downsizing means that real-world fuel economy can be affected by the amount of over-fuelling required to maintain exhaust gas temperatures within acceptable limits. In addition there is a drive to lower the exhaust gas temperature limit in order to reduce the material costs required for high temperature operation. A water-cooled exhaust manifold is one technology, which can be used to minimize the over-fuelling region. This paper investigates the effects of this technology applied to a twin-charger 1.4-liter gasoline direct injection engine. Data is presented which quantifies the benefits in conjunction with other downsizing technologies including cooled EGR and variable geometry turbochargers.