The effects of a broad range of fuel injection strategies on thermal efficiency and engine-out emissions (CO, total hydrocarbons, NOx and particulate number) were studied for gasoline and ethanol fuel blends. A state-of-the-art production multi-cylinder turbocharged gasoline direct injection engine equipped with piezoelectric injectors was used to study fuels and fueling strategies not previously considered in the literature. A large parametric space was considered including up to four fuel injection events with variable injection timing and variable fuel mass in each injection event. Fuel blends of E30 (30% by volume ethanol) and E85 (85% by volume ethanol) were compared with baseline E0 (reference grade gasoline). The engine was operated over a range of loads with intake manifold absolute pressure from 800 to 1200 mbar. A combined application of ethanol blends with a multiple injection strategy yielded considerable improvement in engine-out particulate and gaseous emissions while maintaining or slightly improving engine brake thermal efficiency. The weighted injection spread parameter defined in this study, combined with the weighted center of injection timing defined in the previous literature, was found well suited to characterize multiple injection strategies, including the effects of the number of injections, fuel mass in each injection and the dwell time between injections.
