How to customize feed update time
Appling this function to your function.php file you can edit the updating time of your feed; by this way you can sync your blog with feed more often. To edit time, just need to edit “600″ that mean that feed will be update every 10 minutes. 600 it’s in seconds.
add_filter( 'wp_feed_cache_transient_lifetime', create_function('$a', 'return 600;') );