http://imgur.com/a/W0PR0

First of all, water does not combust. If we, however, assume that they mean that the water is separated into hydrogen and oxygen and the hydrogen is burnt, then it's technically right but still dumb and does not result in a "water powered" car.

Le Chatelier's principle states that the change in enthalpy for a chemical reaction remains the same regardless of the path taken between the products and reactants. In this case, the energy required to separate water (the reactant) into hydrogen and oxygen will be the same as the amount of energy released by burning the hydrogen to form water (the final product). If we assume that the system is designed to convert electrical energy from the battery to heat, and subsequently heat to torque in a standard combustion engine, then this guy has invented a rather shitty and inefficient Tesla.