Viscous stirring of equal-mass planetesimals for increasing close-encounter distance using the group approach. The figure shows root mean square eccentricity (top panel) and inclination (bottom panel) for the same setupas for the equal-mass planetesimal run. Shown are the results of our model for different values of d_ce (coloured lines), a full N-body simulation with mercury (grey), and the semi-analytic model of Ohtsuki et al. (2002; black-dashed).