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Factors influencing the burn rate characteristics of a spark ignition engine with variable valve timing

Most Spark Ignition engines are currently equipped with Variable Valve Timing technology, as sizeable improvements can be gained in efficiency and emissions. Engine control strategies must carefully consider the extent to which combustion is modified by VVT. The paper explores combustion evolution in a gasoline engine with dual-independent VVT, using real-time in-cylinder gas sampling. It identifies fundamental correlations between burning characteristics and relevant operating variables, tested in isolation. At part-load conditions, valve timing influences combustion mostly through changes of charge dilution and density. This publication, outcome of EPSRC funding, was followed by the development of an empirical burn rate model.