Spark assisted compression ignition (SACI) is a combustion mode that may offer significant
efficiency improvements compared to conventional spark-ignited combustion systems.
Unfortunately, SACI is constrained to a relatively narrow range of dilution levels and top
dead center temperatures. Both positive valve overlap (PVO) and negative valve overlap
(NVO) strategies may be utilized to attain these conditions at low and intermediate engine
loads. The current work compares 1D thermodynamic simulations of PVO valving strategies …

As future downsized boosted engines may employ multiple combustion modes, the goal of
the current work is the definition of valving strategies appropriate for moderate to high load
spark ignition (SI) combustion and at low to moderate loads for spark assisted compression
ignition (SACI) combustion for an engine with variable valve timing capability and fixed
camshaft profiles. The dilution and unburned gas temperature requirements for SACI
combustion can be markedly different from those of SI; therefore it is important to ensure that …