Configuration files must be copied to app/config folder.

[keevitaja]

Configuration documentation should clearly state, that in order to change configuration, in most case you must copy the file from core/config to app/config and make the changes there. Ofcauce excluding the ones in the app/config folder which come with the fresh installation of fuelphp.

Also it is worth mentioning, that some configuration can take place in bootstrap.php (extending the core for example)

At the moment there is no refference or information, which configuration files exist and how or where they can be modified. Lot of confusion in that department.