Bought a copy of car mechanics magazine today and read the review of this hydrogen kit. They seemed to really like and apart from the price their doesn't seem to be many downfalls.
"IN BRIEF: The Waterboost System uses spare electricity from your cars alternator to generate Hydrogen and Oxygen gas from water.The Hydrogen and Oxygen is fed into the manifold of your vehicle...The results are astounding, more torque at lower engine speeds, lower emmissions, cooler engine, less carbon build up and considerably more miles per gallon.
The Waterboost System is manufactured in the uk, incorporates all the latest safety features and is designed to last a lifetime ... The Waterboost System was designed, developed and tested by an experienced team of researchers... The system has been fitted locally as a complete system for over 18 months and thoroughly tested by dozens of happy customers using water for fuel.
MORE DETAIL: Hydrogen and Oxygen are generated, on demand, from water, using an electrolysis cell fitted to an alternator. The Hydrogen and Oxygen gas can be added to any internal combustion engine via the air inlet manifold, resulting in faster rates of initiation and subsequent propagation of flames across the whole combustion range. The enhancement of flame initiation and subsequent flame propagation reduces the Ignition delay and combustion period in both spark ignition (eg. Petrol) and compression ignition (eg. Diesel) engines. The chain reaction initiated by the Hydrogen and Oxygen will cause a simultaneous ignition of all the primary fuel. As it all ignites at once, no flame front can exist and without it there is no pressure wave to create knock."
kit costs £500 but is supposed to dramatically improve not only MPG but power and torque as well. The maagzine worked out that a BMW petrol engine would recoup the cost within 16000 miles. It can be fitted to both diesel and petrol. Aside from the initial cost it seems a good piece of kit.
http://cgi.ebay.co.uk/Waterboost-Hydrogen-Fuel-System-HHO-Generator-Kit_W0QQitemZ300308725526QQcmdZViewItemQQptZUK_Car sParts_Vehicles_CarParts_SM?hash=item300308725526& _trksid=p3286.c0.m14&_trkparms=72%3A1689|66%3A2|65 %3A12|39%3A1|240%3A1318