  The transverse momentum dependence of elliptic flow of pions calculated in a
full (3+1)d Boltzmann approach with an intermediate hydrodynamic stage for
heavy ion reactions for CERN-SPS energies is discussed in the context of the
experimental data. At higher SPS energies, where the pure transport calculation
cannot account for the high elliptic flow values, the smaller mean free path in
the hydrodynamic evolution leads to larger elliptic flow. Due to the more
realistic initial conditions and the incorporated hadronic rescattering the
results are in line with the experimental data. Within this integrated
dynamical approach different equations of state are applied without adjusting
the initial state and the freeze-out conditions. We employ a hadron gas
equation of state to investigate the differences in the dynamics and viscosity
effects, a chiral equation of state with a moderate first order phase
transition and a critical endpoint and a bag model equation of state with a
large latent heat. The elliptic flow results are shown to be rather insensitive
to changes in the equation of state.
