To meet the mandatory CO2 emissions regulations in the future, current gasoline engines require significant work for efficiency improvement. One critical part of combustion optimization is to improve the spark ignition process, especially for the engines that utilize charge dilution concept incorporated with strong cylinder flow. Such high efficiency combustion process requires the ignition systems to effectively ignite the mixture and secure the flame kernel until developing to self-sustainable propagation. In this paper, the extent of spark stretching and the ability to withhold from restrike in high-speed flow are investigated for various sparking strategies. A thick plasma channel that is generated by boosted glow current is less prone to be blown off by the strong flow, consequently, the restrike frequency is lowered. In comparison with a low current long lasting spark generated by the dual-coil continuous discharge strategy, the boosted current strategy can lead to a faster flame kernel growth. Single-cylinder engine experiments indicate that the combustion phasing controllability and the stability of lean/diluted engine operation can be improved by using the boosted current ignition strategies with conventional spark plug. Extensive engine test results indicate that the multi-core ignition can better control the gasoline combustion and extend the operable limits of lean/diluted engine combustion, compared with single-pole ignition for low to medium engine loads. Experimental results indicate that the multi-core ignition strategy, even with lower current on each pole, have clear advantages over the high current single-pole strategies such as the multi-coil ignition and the boosted current ignition, with respect to the combustion phasing controllability of super lean gasoline combustion. Multiple-cylinder production gasoline engine test results show that the multi-core ignition can improve the stability of gasoline engine at high levels of dilution, thereby leading to improvement of indicated specific fuel consumption
