A new beta-adapted capture cavity will be installed at the S-DALINAC injector. For a successful commissioning after the installation of the upgrade, detailed studies of longitudinal beam dynamics along the injector are crucial. The dependency of the electron bunch characteristics of the injector on cavity settings as well as input parameters yields important information for the first setup of this accelerator section. Furthermore, the low-energy acceptance will be investigated. Following the obtained set of simulations, the found parameters are planned to be verified experimentally as part of the characterization of the new injector setup.