  We simulate the central reactions of $^{20}$Ne+$^{20}$Ne,
$^{40}$Ar+$^{45}$Sc, $^{58}$Ni+$^{58}$Ni, $^{86}$Kr+$^{93}$Nb,
$^{129}$Xe+$^{118}$Sn, $^{86}$Kr+$^{197}$Au and $^{197}$Au+$^{197}$Au at
different incident energies for different equations of state (EOS), binary
cross sections and different widths of Gaussians. A rise and fall behaviour of
the multiplicity of intermediate mass fragments (IMFs) is observed. The system
size dependence of peak center-of-mass energy E$_{c.m.} ^{max}$ and peak IMF
multiplicity $<$N$_{IMF}>^{max}$ is also studied, where it is observed that
E$_{c.m.}^{max}$ follows a linear behaviour and $<$N$_{IMF}>^{max}$ shows a
power law dependence. A comparison between two clusterization methods, the
minimum spanning tree and the minimum spanning tree method with binding energy
check (MSTB) is also made. We find that MSTB method reduces the
$<$N$_{IMF}>^{max}$ especially in heavy systems. The power law dependence is
also observed for fragments of different sizes at E$_{c.m.} ^{max}$ and power
law parameter $\tau$ is found to be close to unity in all cases except
A$^{max}$.
