Im assuming you want to close the modal after x seconds.
So.
function modal_form_success()
{
setTimeout(function(){
jQuery('.modal.active').emodal('close');
}, x);
}
and then in your forms callbacks
on_sent_ok: modal_form_success()
There are a couple of commands you can use with the emodal() function
close
,open
and center
to name a few. For open though best to use the modals id eModal-#
as a selector instead of .modal.active.