[9] Due to the inherent complexity of these subsystems, a necessity of modern engine design and emissions standards, such claims made by proponents of hydrogen fuel enhancement are difficult to substantiate and always disputed.
"[11] They do, however, point out that installation of such devices often involves illegally tampering with an automobile's emissions control system, which could result in significant fines.
Hydrogen fuel enhancement from electrolysis (using automotive alternators) has been promoted for use with gasoline-powered and diesel trucks,[14][15][16] although electrolysis-based designs have repeatedly failed efficiency tests and contradict widely accepted laws of thermodynamics (i.e. conservation of energy).
Proponents, who sell the units (often called "HHO devices"), claim that the dynamics are often misconstrued, and due to the chemical properties of the resulting mixture, it is possible to gain efficiency increases in a manner that does not violate any scientific laws.
Those unfamiliar with electrodynamics may not realize that the electrolytic cell drains current from a car's electrical system, causing an increase in mechanical resistance in the alternator that will always result in a net power reduction.