There are plans all over the internet that show you how to build HHO, or Brown's Gas, generators.  Some call it Hydroxy for the 'hydrogen and oxygen' gas developed when water is electrolyzed with no separation of the gases.  Make sure you understand that this isn't just hydrogen but the results of electrolysis and is very volatile.

You should be completely familiar with all the warnings, cautions, dangers, procedures and techniques associated with HHO gas.  We highly encourage you to explore every vantage point you can, and not just those linked on this site, to make sure you have a good understanding of the task at hand.   You should also be forwarned about using the gas.  Remember burning HHO creates high temperatures and water vapor, if not water outright.  Remember what 90% of the internal combustion engines on the planet are made out of?  Iron.  Steel and Iron.  Hot Water + Steel = Rust.  That's why you will also see hybrid designs out there too.  They are attempting to keep the water in a vapor state further down the exhaust stack. 

If you are interested in augmenting or converting your existing vehicle it is possible.   If you like tinkering around in the garage, find an old klunker somewhere and experiment.  Things to consider on a project of this sort:

• HHO Generator Electrical Circuits
• Making your HHO Generator
• Electrolyser (Electrolyzer)
• Electrolyzer Electronics
• 316L Stainless Steel
• Find yourself an old car that runs good
• If you're soldering your own circuits you'll need a soldering tool
• Once you have decided on your electronics you'll need a board to mount them on.  There are many custom printed circuit board companies out there.
• Oscillator Circuits