You do not have to get a new engine to run your car on water. If you wanted a water car, you will just use the old engine and fix a convertor on it. The converter is the device that would turn the water into gas.  Aside the converter, you do not have to do any other changes to your engine. 

This new engine has become quite ideal for drivers who need to economize on fuel. Now, they will have to fill their cars with water and not gasoline. You will only use ordinary water and have it recycle by the system over and over again. This means, you will be able to have more miles.