The Engine section of the performance menu in Need for Speed: Unbound allows players to remove and replace the engine equipped in any of their owned cars with a different engine.
The selection of available engines differs depending on the car owned and players aren't required to own a donor car in order to swap an engine.
Each engine has differing horsepower output, displacement, number of cylinders, cylinder orientation, aspiration, and upgrade potential.
An engine has both a stock horsepower rating and a potential upgraded horsepower rating, as well as a listed stock 0 to 60 mph time, top speed, and amount of torque produced.