Aftermarket fuel economy device: Wikis

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Encyclopedia

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. Tests by Popular Mechanics confirmed that these types of devices yield no measurable improvements in fuel consumption or power, and in some cases actually degrade both power and fuel consumption.[1]

Many other reputable organizations such as the AAA [1] [2] [3] [4] and Consumer Reports [5] have performed studies that have found similar results.

Thermodynamic Efficiency

The reasons that many of these devices are impossible (especially alleged 100MPG or 300MPG devices) are based on thermodynamics. This formula [2] 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-air combustion), the theoretical efficiency of the engine would 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 is 300% efficient, which violates the Second Law of Thermodynamics.

Extremely efficient vehicle designs capable of achieving 100MPG+ (such as the VW 1l) do not have significantly greater engine efficiency, but instead focus on better aerodynamics, reduced vehicle weight, and reusing energy expended during braking.

Urban legend

There is a related urban legend about an inventor who creates a 100 mpg (2.35 L/100 km) 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 U.S. Patent 1,750,354 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. [6]

Australian motor racing legend Peter Brock marketed one such device in the 1980s, creating significant damage to his reputation in the Australian motor industry.

References

1. ^ Looking For A Miracle: We Test Automotive 'Fuel Savers', Popular Mechanics, September 2005
2. ^ "Improving IC Engine Efficiency". University of Washington. Retrieved June 4, 2008.

Improving IC Engine Efficiency [7]