Synchronization of combustion variations in a multicylinder spark ignition engine

We report experimental observations of synchronization among combustion variations in different cylinders at fuel-lean conditions in an eight-cylinder spark ignition engine. Our results appear to confirm that synchronization readily occurs and that it becomes stronger as the overall equivalence ratio is reduced from stoichiometric. It also appears that the onset of synchronization is associated with bifurcation instabilities reported previously for combustion in single cylinders. We use both cross-correlation and symbolic time series analysis to quantify the apparent relationships between pairs of cylinders and multicylinder groups. Extension of a simple dynamic model for single-cylinder combustion variations to the multicylinder case appears to agree with the observations and provides a basis for further studies, The occurrence of significant cylinder-to-cylinder synchronization may have significant implications for engine diagnostics and control.