Modeling cycle-to-cycle variations in spark ignited combustion engines by scale-resolving simulations for different engine speeds

•Cyclic variation is numerically investigated in a spark-ignited lean gas engine.•The cyclic variations are explained using local flame analysis.•Turbulence around the early flame front is the major contributor to the observed CCV.•Flame kernel is more prone to local conditions when it is small.•The higher the RPM, the longer the initial effects may persist in CAD time.