I have just notice that parameter Timestep in the OpenStudio settings is not being used in the simulation. For example, if I choose 6, this step is ok in the .osm file:
OS:Timestep,
{210f49e8-ab04-4b81-b6fd-0fac6eeadcbc}, !- Handle
6; !- Number of Timesteps per Hour
But in the in.idf file it will always remain 4:
Timestep,
4; !- Number of Timesteps per Hour
Am I missing something? I guess the only workaround is to write a energyplus measure to modify this value.