CakePHP Session Expires - Frequently

I am using CakePHP 1.3 and in core.php. I set the following settings

Configure::write('Security.level', 'low');

Configure::write('Session.timeout', '12');

But after logged in,开发者_如何学JAVA its frequently logged out. I am not using auth component

Session.timeout - Base session timeout in seconds. use

Configure::write('Session.timeout', 12 * 60 );