Paul is right, but I have to add to the discussion.
I did an article about autorotations with the engine at idle not being the same as with the engine stopped. I carefully did not mention any types, as I wasn't sure this was applicable to all.
A large helicopter manufacturer in Texas took exception to the article, and went and proved there was no measurable difference in the performance or handling with the engine at idle or off. This was pretty gutsy, but they now do an annual engine really failed autorotation with each of their instructors.
So while the contribution of the engine at idle may be there on some helcopters, it's not there on all of them!