Page not found - %20 in url

The base_url setting is not used by either the URI class or the Router class, it is used to generate URLs, not to resolve/route them.

You may need to set $config['uri_protocol'] to 'PATH_INFO' or modify the .htaccess file to set RewriteBase /api/ to get the URI passed to your application to be relative to the /api/ path.

Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide