Scatter plots of the total flame surface value computed at −10 CAD as a function of the high frequency kinetic energy spatially averaged on a 2D disk of radius 3 mm around the spark plug. For each point the corresponding cycle number is indicated in the figure. The Pearson product-moment correlation coefficients of the two variables are also shown in the title. Upper figure: EC is computed considering the two velocity components within the central tumble plane. Lower figure: the third velocity component (normal to the central tumble plane) is also added in the EMD analysis.