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Compared to conventional homogeneous direct injection or port-fuel injected engines, the second generation, spray guided, direct injection engine (SGDI) has the potential for significantly improved fuel economy during part load stratified charge operation. Multiple fuel injection strategies can be utilised to increase the unthrottled operating range, leading to further improvements in fuel economy. However, careful optimisation of these strategies is essential to ensure that benefits are maintained whilst further minimising emissions within combustion stability limits and consumer driveability demands. The effects of multiple injection strategies upon fuel consumption, emissions and combustion stability were investigated in a single cylinder Ricardo Hydra engine with a spray guided combustion system. An outwardly opening piezoelectric actuated injector was employed. The fuel injection strategy utilised up to five injections per engine cycle.

This paper describes an investigation of emissions from an engine featuring variable valve timing, a swirlcontrol valve and exhaust gas recirculation. Design of experiments has been used to model the response of hydrocarbons and other emissions to the engine operating variables. The experiments identified the potential of VVT for simultaneous NOx, and HC reduction. The type of experiment employed was the Central Composite Rotatable Design; this is a fractional factorial design that maximises the amount of information obtained from a minimal number of test runs. A Fast Response Flame Ionisation Detector has been used to clarify the reasons for the effect of inlet and exhaust VVT on hydrocarbons.

Carbon fiber reinforced carbon (CFRC) composites possess high specific strength, without loss of strength at high temperatures. The fiber architecture of these composites can be manipulated to yield tailored mechanical and thermal properties. Because of their light weight and the above attributes, these composites are attractive for pistons and other reciprocating parts in internal combustion engines. However, few tests have been performed to test these pistons for structural integrity and engine performance. Testing was undertaken to assess the basic suitability of this material for use in a spark-ignition engine. Of particular were basic mechanical function and combustion effects. With the CFRC piston cylinder, hydrocarbon emissions were higher, IMEP lower and the higher piston temperature induced detonation prematurely. The increase in hydrocarbon emissions was attributed to higher crevice volumes under hot operating conditions and fuel adsorption/desorption into the piston crown.