Study on spark assisted compression ignition (SACI) combustion with positive valve overlap at medium-high load

► The influences of PVO configuration on gas exchange and SACI combustion are investigated. ► The PVO and eEGR determine the load and thermal state in-cylinder. ► LEVC strategy achieves higher thermal state in-cylinder than EIVO strategy does. ► Smaller PVO combined with higher eEGR performs better fuel economy in stable combustion region. ► Optimized PVO and eEGR strategy is proposed to improve the SACI combustion in the range of 5-9 bar.