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This SI engine research investigation extends a previous study [14] concerning one kind of non-conventional firing device: the Pulsed Jet Combustion (PJC) igniter. The PJC device was compared to a conventional spark plug during operation in a 4-valve single cylinder engine at 2000 rpm and a variety of air/fuel ratios and loads. Additionally, skip-firing was used to vary the residual gas rate. The mass fraction burned intervals were calculated from the pressure trace for each cycle via a heat release analysis that accounted for cycle-to-cycle variations in the trapped mass of fuel. Statistical analyses were performed for 100 cycles of operation for each test condition. Similar results were found for the PJC device as for the spark plug with zero residual (five skipped cycles). For both igniters, the cycle-to-cycle variability increased with increasing residual, but the variability was less pronounced for the PJC device.

This paper reports on an experimental investigation of an SI single cylinder engine cycle-to-cycle variations. Two different ignition devices are studied: a spark plug and a non conventional ignition device, PJC (Pulsed Jet Combustion). In-cylinder pressure is analyzed via a complete heat release rate computation. A significant decrease in IMEP cycle-to-cycle variations can be achieved only when the initial burning rate is enhanced with PJC device for example. The cycle-to-cycle combustion variations (CA01, PMax, IMEP) are not improved in the same proportions. The PJC is a firing device which meets the objective of repeatable ultra-lean mixture ignition and development of combustion, but slightly lowers the global efficiency due to the increase of heat losses for high load running points.