From Civilization V Wiki
- Special Improvement
You can expend an Engineer to create a Manufactory. A Manufactory produces huge amounts of production (hammers) for the city, if it is worked.
- Special Ability
- Hurry Production
You can expend a Great Engineer to create a sudden burst of production in a city. The production is immediately applied to whatever is presently being built in the city – unit, building or Wonder. This will usually be enough production to immediately finish all but the most massive Wonders, and it will drastically shorten their production time.