Synchronize login details in 2 Vanilla forums

I have 2 forums in 1 domain, each one displaying different relevant information which I control with the ExcludeCategories and HideCategory plugins. The 2 forums share the same mysql database in order to keep the users and login details for both the same. I was hoping that It happens when login to the one forum, then go to the other forum you will not need to login again. However this is not happening. I suspect the login scripts of the 2 forums are different which causes this. Any idea how I can overcome this problem? It also happens when you are returning to the first forum you need to login again although I have ticked the "stay login " box. I am trying to stay away from jsconnect as I think this is a overkill for this purpose. Any advice will very much be appreciated. Thanks.
Answers
Got it thanks. I changed the cookie in the config.php file of the 2 forums to the same value.
$ Configuration ['Garden'] ['Cookie'] ['Salt'] = 'qwerty';
$ Configuration ['Garden'] ['Cookie'] ['Domain'] = ' ';
Only do this if you have the same user table.
grep is your friend.