We present results of cosmological simulations of disk galaxies carried out with the GADGET-3 TreePM+SPH code , where star formation and stellar feedback are described using our MUlti Phase Particle Integrator ( MUPPI ) model . This description is based on a simple multi-phase model of the interstellar medium at unresolved scales , where mass and energy flows among the components are explicitly followed by solving a system of ordinary differential equations . Thermal energy from SNe is injected into the local hot phase , so as to avoid that it is promptly radiated away . A kinetic feedback prescription generates the massive outflows needed to avoid the over-production of stars . We use two sets of zoomed-in initial conditions of isolated cosmological halos with masses ( 2 - 3 ) \cdot 10 ^ { 12 } M _ { \odot } , both available at several resolution levels . In all cases we obtain spiral galaxies with small bulge-over-total stellar mass ratios ( B / T \sim 0.2 ) , extended stellar and gas disks , flat rotation curves and realistic values of stellar masses . Gas profiles are relatively flat , molecular gas is found to dominate at the centre of galaxies , with star formation rates following the observed Schmidt-Kennicutt relation . Stars kinematically belonging to the bulge form early , while disk stars show a clear inside-out formation pattern and mostly form after redshift z = 2 . However , the baryon conversion efficiencies in our simulations differ from the relation given by ( ) at a 3 \sigma level , thus indicating that our stellar disks are still too massive for the Dark Matter halo in which they reside . Results are found to be remarkably stable against resolution . This further demonstrates the feasibility of carrying out simulations producing a realistic population of galaxies within representative cosmological volumes , at a relatively modest resolution .