CodeIgniter XML-RPC request formating

i'm trying create XML request to remote server with CodeIgniter. I need create formated call like this:

<?xml version="1.0" encoding="utf-8"?>
    <request name="get_packmachine">
      <auth username="test" password="test" />
    </request>

My current Code Igniter code:

                    $this->load->library('xmlrpc');

                    $this->xmlrpc->server($gate, 80);
                    $this->xmlrpc->method('get_packmachine');

                    $request = array('get_packmachine' => array('auth'=>array('username'=>'test','password'=>'test')));
                    $this->xmlrpc->request($request);

But it's returning still some errors. Is it possible make call like in my example with this CI library?