Got maybe a 10% mpg gain with my DIY HHO generator last full tank. This is in a 1.5 L Toyota carbed vehicle (non-working feedback carb). This tank was during fairly cool spring weather and the generator was only drawing from 3 to 5 amps....while it is designed to run at up to 10-12 amps.
This is a small form-factor design that should fit in most vehicles....but needs a cooling air flow. Probably best for engines around 1.5 L to 1.8 L or less? Still need to test it for gas output.
Will test it again this summer to see what temps it runs at and at a higher amperage. Higher amps won't necessarily mean better mpg gains?
Can see it here:
http://oupower.com/index.php?dir=_Other ... cts/fixaze
In warmer weather I have noticed more pinging...but it is livable.