Fuel Vapor Injectors
Gasoline's ability to burn changes along with its physical state: In liquid form, it burns too slowly to be useful for combustion. But when vaporized, gasoline burns at the explosive rate needed to power an internal combustion engine. Hucksters have been leveraging this fact for years.
One of the more common gadget hoaxes on the market is the fuel vapor injector. Allegedly, this device converts the fuel into a fine vapor before it reaches the engine, which supposedly lets the fuel burn more efficiently.
The problem with these devices comes not at the point of ignition, but at the tail end of the modern car or truck. An exhaust sensor measures the amount of oxygen in the vehicle's exhaust, which can indicate whether the engine is taking in the correct fuel-to-air mixture. Adding extra vaporized fuel through a vapor injector can cause the engine to run rich, with too much fuel and not enough air. The engine's computer would then adjust its fuel injectors to achieve the proper fuel-to-air ratio. At best, this means the engine would run exactly the same as it did without the vapor injector. At worst, a poorly installed vapor injector could cause part of the cylinder bank to run rich, sapping engine performance as the computer makes additional adjustments to address the imbalance [source: Allen].