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Gasoline engine downsizing has become a popular and effective approach to reduce CO2 emissions from passenger cars. This is typically achieved in the form of a boosted direct injection gasoline engine, which are typically equipped with variable valve timing (VVT) devices on the intake and/or exhaust valves. This paper describes the synergies between valve timings and boost based on experimental investigations in a single cylinder gasoline direct injection spark ignited (DISI) engine with variable cam phasing on both the intake and exhaust cams. Two cam profiles have been tested to realize Miller cycle and compared with the standard camshaft. One cam features a long opening duration and standard valve lift for Late Intake Valve Closing (LIVC) and the other cam has a short opening duration and low valve lift for Early Intake Valve Closing (EIVC).

An unmodified, conventionally fuelled, 2009 Class D vehicle with a 2.0L turbocharged gasoline direct injection engine was operated on a range of gasoline, gasoline-ethanol and gasoline-butanol fuel blends over NEDC drive cycles and WOT power curves on a chassis dynamometer. Engine performance, engine management system parameters and vehicle out emissions were recorded to investigate the response of a current state-of-the-art technology vehicle to various alcohol fuel blends. The vehicle fired on all fuels and was capable of adapting its long term fuelling trim to cope with the increased fuel flow demand for alcohol fuels up to E85. Over the NEDC tests, the volumetric fuel consumption was very strongly related to the calorific content of the fuel. CO and NOx emissions were largely unaffected for the mid alcohol blends, but CO emissions decreased and NOx emissions increased significantly for the high alcohol fuels. THC emissions were largely unaffected.

The main focus nowadays for the development of future vehicle powertrain systems is the improvement in fuel efficiency alongside the reduction of pollutant emissions and greenhouse gasses, most notably carbon dioxide. The automotive community is already engaged in seeking solutions to these issues, however, the ideal solution, namely zero emission vehicle is still regarded as being a long way from fruition for the mass market. In the meantime steps are being taken, in terms of engineering development, towards improved fuel efficiency and sustainability of relatively conventionally powered vehicles. One approach to the decarbonization of road vehicles is to supplement existing fossil fuels with sustainable biofuels.

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 effect on the intake flow field, air fuel mixing processes, thermodynamic performance and emissions output has been investigated for a range of valve operating profiles. A standard speed load point of 2000 rpm and 2.7 bar IMEP720° has been reached by throttling the intake whilst running standard cam profiles, by early closing of both inlet valves (EIVC) and by early closing of each inlet individually to generate bulk swirl motions within the cylinder. Data has been recorded at stoichiometric air fuel ratios for both direct injection and port fuelled operation. The valve profiles have been applied to two single cylinder homogeneous gasoline direct injection (GDI) spark ignition engines, developed to investigate the potential of controlling engine load by limiting the inducted air mass using fully variable valve timing (FVVT) to reduce pumping losses at part load.