Identifying this turbine piece with a stud and a Technic axel I promise that I don't simply dump photos on here without researching them.  I've been using Bricklink's system for 15 years, and it still perplexes me occasionally...such as this bizarro part.  

I swear I went though nearly every possible category this weekend (and all of the Technic groups), and I can't find it.  

Can anyone please help?
It's part 4869 - Engine, Smooth Large, Center.