Water as a fuel? High school chem

It is a old con game heres how it works. you have an car or truck and fill the gas tank with water then drop in a pill. start the car and drive away. Now here is the con. the pill is the same pill a miner places in his mining lamp. When that pill hits the water it combinds with the water to produce ACETYLENE GAS this gas is then vented from the top of the tank and piped to the engine and runs just like a propain powered car. It works like a charm and every one thinks your Merlian. However it is not a cheap fuel.