The idea is good but Hydrogen explodes when contacted with oxygen without needing to ignite it. Unless you have a sealed Hydrogen container, I wouldn't try unless you want your car to blow up.

 

??? We would all be dead if that were the case.

 

For hypermiling techniques, we discuss a bunch in my Hypermiling the ralliart thread.

The general consensus is that this power your car from water thing is a scam, just like that electric turbo add on a few years back. Water is a very, very stable molecule and takes energy to break it down. No doubt, you could reduce gas use by burning hydrogen. If it was a plug in system than maybe it would be more economical as electric is cheaper than gas right now. There is a "Water Powered" car in japan that hit reuters last month. They're saying that they're using hydrogen to power batteries that run the electric car. I'm not 100% sure if thats a scam or not but its interesting to follow. The Honda Clarity HCX is out now in southern california and looks pretty cool. Thats the only hydrogen fuel cell powered car out though thats legit in my book.

 

Wow. Take a chemistry class.