Route 404 Over Ride sub directory issue

As mentioned in the user guide:
http://www.codeigniter.com/user_guide/ge...ved-routes

Same per-directory rules as with ‘default_controller’ apply here as well.

So, the 404_override setting defines a controller/method pair only, just like the default_controller setting. An error directory containing a not_found controller would only be called if the $RTR->directory was already set to 'error' by the route it was attempting to resolve and 404_override was set to 'not_found'.

Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide