The engineer title is more defined and goes along engineering titles in other areas. (In America at least).
I think the developer title relates more to the ground worker who does the work described by the engineer, it's just another word for worker as I see it, but I might be a bit off.
An engineer is someone who use the tools (algorithms) and build something new. In other words an engineer can design the software.
Then there's scientist who does the research part and invent new tools (algorithms)