I see these things all the time, but do they really work? They are supposed to help with increased fuel economy.

Here's an example of one:

http://cgi.ebay.ca/GMC-Supercharger-...QQcmdZViewItem

 

I found a good explaination of such devices, if anyone is interested:

"There are a lot of products on the market that promise similar things, such as the "Tornado Fuel Saver" among others, claiming to increase power and fuel economy by as much as 20%.

Is it true?

For simplicity, I'll use the Tornado as the example here. Here is the basis for their claims: Normally air entering your intake does not mix well with fuel, leaving an uneven mix of air and fuel as it enters the combustion chamber, hindering efficiency. The Tornado creates a vortex of air entering the intake, and the swirling air promotes better fuel atomization, unlocking potential in your car's engine.

Problem is, that's not how it works.

First off, you normally want less turbulence in your intake, not more -- a turbulent air stream will have less throughput than a calm stream. Companies will claim that a perfect vortex will speed up the air, and while this is true, there is no way that this device will create a perfect vortex in the irregular shape of the intake manifold. As an example, polishing the intake to make the inner surfaces smoother (and reducing turbulence) will usually result in increased performance. And even if the vortex somehow managed to help, the Tornado is, on a lot of cars, installed far upstream of the engine near the air filter. The vortex of air has no chance of lasting long enough to make it into the combustion chamber.

Secondly, if a simple little device like this could unlock such potential, why wouldn't they be installed on all cars from the factory? Automakers would benefit greatly from increased MPG figures for their vehicles. Answer is, they would. This device simply doesn't work, and in some cases reduces efficiency and horsepower because it restricts the airflow.

Modern engines are efficient. They burn about 99% of the fuel present in the combustion process. This only leaves 1% potential to increase fuel atomization and efficiency. This is not to say the modern engine converts 99% of the energy in gasoline to mechanical motion - much is lost as heat and friction. But the energy in the gasoline is released.

Other products that claim to also create vortexes are just as flawed, such as many throttle body spacers. The vortexes these are said to create have the same issues as the Tornado mentioned above, although these have a side effect of increasing plenum volume with may or may not increase performance. In most cases there won't be much of an effect unless there have been modifications done to the engine.

Slightly different (but similar) products claim to create turbulence in the intake by pulsing air using a special one-way valve. Again, turbulence is bad, not good, and needless to say these products do not work. They can also be dangerous as they are often spliced into your brake vacuum booster line. Not something you want to lose vacuum on while driving.

I have personally tried one of these air pulsing valves, called the Ecotek. It made a loud sucking noise but that's about it. Actually, it made my car fail emissions by a huge margin. Oxides of nitrogen (NOx) quadrupled from about 94 to 400, CO increased, and HC's increased as well. The engine management computer doesn't know how to deal with an addon like this and cannot effectively control the engine with one.

If you want to save gas, don't waste your money. Keep your tires inflated, your air filter clean, and your engine running properly.
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Guide ID: 10000000001966129Guide created: 10/03/06 (updated 03/27/08)"[/align]