All kids are different. I have to wake my Z from every nap now he is on one, but getting there was hard, we would have some 45min ones, some 1.5hrs (for us this was OT) and some 3 hr ones.
I think really for most toddlers 13-14 hrs sleep is average, but it is important that they get both a good night and nap/ KWIM? That said some kids just dont nap for long periods ever, but are great night sleepers. Go with what works for you and your LO and if you feel that 1.5hrs is all he needs and he is doing 13hr nights and is well rested that may be his rhythm.