Aftermarket fuel economy device

An aftermarket fuel economy device is a device sold on the aftermarket that claims to improve the fuel economy and possibly the fuel emissions of a vehicle. There are a large variety of devices sold under names such as "Platinum Gas Saver", "Tornado Fuel Saver", "Cyclone Fuel Saver", "Cyclone-Z", "Atomized Vapor Injector", "Turbo-carb" or "ZEFS".

There are several different designs, but many are designed to fit on the intake or carburetor of a car and purportedly optimize air or fuel flow in some way. They are often sold via late-night infomercials, at prices ranging from $20 to over $100 each.

The US EPA is required to test many of these devices under Section 511 of the Motor Vehicle Information and Cost Savings Act, and to provide public reports on their efficacy. Most devices on the market are not found to improve fuel efficiency to any statistically measurable extent.

Many other reputable organizations such as the AAA [http://www.aaa.com/news12/Automotive/Autogram/!page1.pdf] [http://www.aaa.com/news12/Automotive/Autogram/!page2.pdf] [http://www.aaa.com/news12/Automotive/Autogram/!page3.pdf] [http://www.aaa.com/news12/Automotive/Autogram/!page4.pdf] and Consumer Reports [http://www.consumerreports.org/cro/cars/maintenance-accessories/gassaving-devices-904/overview/index.htm] have performed studies that have found similar results.

Thermodynamic Efficiency

The reasons that such devices are impossible (especially alleged 100MPG or 300MPG devices) are based on thermodynamics. This formula [cite web |url=http://courses.washington.edu/me341/oct22v2.htm |title=Improving IC Engine Efficiency|publisher=University of Washington |accessmonthday=June 04 |accessyear=2008 ] has been derived to give us the theoretical efficiency for an engine:

:$h\; =\; 1\; -\; \{1\; over\; rv^\{g-1$

where h equals efficiency, rv equals the volume ratio (Compression Ratio) and g represents the ratio of the specific heats of the gases before and after combustion.

Assuming an ideal engine with no friction, perfect insulation, perfect combustion, a compression ratio of 10:1, and a g of 1.27 (for gasoline), the theoretical efficiency of the engine would only be 46%.

For example, if an automobile typically gets 20MPG efficiency with a 20% efficient engine that has a 10:1 compression ratio, a carburetor claiming 100MPG would have to increase the efficiency by a factor of 5, to 100%. This is clearly beyond what is theoretically or practically possible. A similar claim of 300MPG for any vehicle would require the engine (in this particular case) that 300% efficient, which clearly violates The Second Law of Thermodynamics.

Urban legend

There is a related urban legend about an inventor who creates a 100 mpg (2.35L/100km) carburetor, but after demonstrating it for the major vehicle manufacturers, the inventor mysteriously disappears, in which he may have been killed by the government. The urban legend is thought to have started after Charles N. Pogue filed US patent|1750354 for such a device. Though the legend has a basis in reality, it's unlikely that there has been a conspiracy to hide such an invention. [http://www.snopes.com/autos/business/carburetor.asp]

ee also

* Catalytic carburetor
* Powertrain
* Fuel saving devices

References

Improving IC Engine Efficiency [http://courses.washington.edu/me341/oct22v2.htm]

External links

* [http://www.epa.gov/otaq/consumer/reports.htm EPA reports on Emission Reduction Devices Evaluation]
* [http://www.cnn.com/2006/AUTOS/tipsandadvice/05/02/conned_for_mpg/index.html CNN: Gas prices up. So are scams.]
* [http://www.cnn.com/2006/TECH/science/08/07/gas.saving.investigation/index.html CNN: No shortcuts to saving money on gas.]
* [http://blog.sfrcorp.com/2007/06/20/fuel-is-better-quality-these-days-i-heard-additives-are-no-longer-needed-is-that-true/ Major automakers are requesting more additives in today's poor quality fuel]
* [http://www.rand.org/pubs/technical_reports/TR313 | Rand Corporation: An Approach to Assessing the Technical Feasibility and Market Potential of a New Automotive Device] ]
[Category:Urban legends]