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The methods of operation of four of the leading combustion system designs for fuel only gasoline direct injection (G-DI) engines have been compared by applying a classical analysis procedure for defining fuel transport. The fuel spray requirements for the different systems are discussed in relation to results obtained from a Phase Doppler Anemometry (PDA) rig for different injectors. The combustion systems have then been considered regarding the functional requirements of future G-DI engines. These include power potential, stratified and homogeneous performance, variable air motion requirements, OEID component function monitoring, packaging and manufacturing issues and calibration effort. The paper concludes that there are at least four main approaches capable of producing acceptable combustion and that the choice of system will depend on packaging, cost and manufacturing constraints.

A system for stratifying recycled exhaust gas (EGR) to substantially increase dilution tolerance has been applied to a multi-cylinder port injected four-valve gasoline engine. This system, dubbed Combustion Control through Vortex Stratification (CCVS), has shown greatly improved fuel consumption at stoichiometric conditions whilst retaining ULEV compatible engine-out NOx and HC emission levels. A production feasible variable air motion system has also been assessed which enables stratification at part load with no loss of performance or refinement at full load.

This paper describes an experimental investigation to explore and optimise the performance, economy and emissions of a direct injection gasoline engine. Building on previous experimental direct injection investigations at Ricardo, a single cylinder engine has been designed to accommodate common rail electronically controlled fuel injection equipment together with appropriate port configuration and combustion chamber geometry. Experimental data is presented on the effects of chamber geometry, charge motion and fuel injection characteristics on octane requirement, lean limit, fuel consumption and exhaust emissions at typical automotive engine operating conditions. The configuration is shown to achieve stable combustion at air/fuel ratios in excess of 50:1 enabling unthrottled operation over a wide operating range. Strategies are demonstrated to control engine out emissions to levels approaching conventional port injected gasoline engines.