Not every router has this option. This just means that you'll have to tweak your torrent program's setting instead.
What is the number of connections your torrent program allows? It may be something that your router just can't cope with. Also, try limiting d/l and u/l max speeds.
All that said, the simplest fix would be to just turn off torrenting when you are trying to do something else. Let it run overnight, or during the day when you're at work or school or whatever.