Flexible Fuel Technology: Flex Engines

Flex engines aren't wildly different from gasoline engines, nor are they space-age technology. The Ford Model T car, for instance, was a flex engine that burned either gas or ethanol.

FFVs don't cost more to build, and they aren't more expensive in terms of sticker price, either. If you really want to, you can even buy a conversion kit that lets you turn your gasoline motor into one that will happily drink E85.

From a chemical perspective, ethanol is different from gas in two major ways. It's more corrosive and conductive. It also burns hotter, so it has a higher octane rating. A flex engine must be built to handle those technical challenges.

For starters, your car has to know what kind of fuel you're pumping. An onboard computer analyzes fuel composition to optimize engine ignition, adhere to emissions standards and regulate combustion. No matter how much the ethanol-to-gas ratio fluctuates, your flex-fuel car can adjust on the fly.

In flexible-fuel vehicles, the fuel tank and in-tank components are built to withstand ethanol's corrosiveness. Similarly, the fuel lines, gaskets, seals and rubber fuel hoses all must be corrosion-resistant, too, as must the fuel injectors.

The same goes for internal engine components. Valve seats, piston rings, valves and other parts are all made from materials that won't easily corrode. These parts are also built to diminish the possibility that damage will result due to ethanol's tendency to break down and clean away engine lubricants.

Conductivity is another concern. All electrical parts of the fuel system, including wiring, must be insulated against ethanol's higher conductivity. In addition, the fuel filler parts have anti-spark features that reduce the chance of stray sparks or static electricity causing a dangerous flare-up.

Electrical worries aside, ethanol has a lower energy density than gasoline, so the engine needs more fuel to achieve high performance. Thus, fuel injectors are created to achieve higher fuel flow rates --otherwise, your engine would see a drastic reduction in overall power.

In terms of engine construction, those are the most notable distinctions in FFV motors. On the next page, you'll read more about flex engine performance and whether making the switch is logical for you.

For multiple reasons, the eco-friendliness of FFVs is questionable. Cost savings are dubious, too. And as it turns out, it's not necessarily consumer demand or sustainability concerns that are driving the proliferation of FFVs.

Let's start with the basics. There's no change in vehicle performance when you use ethanol. You won't notice a difference in acceleration or horsepower.

The key differences are energy density and CO2 (carbon dioxide) emissions. Lower energy density just means that there's less energy in a gallon of ethanol than there is in regular gasoline, so you have to burn more to travel the same distance that you would with gas.

This, in turn, means you have to burn more fuel to get moving, and your vehicle actually releases more CO2 than it does with gas. However, because that CO2 was derived from a plant source instead of petroleum, you're (in theory) simply releasing it back into the atmosphere, where it would have gone anyway as the plant naturally decayed. Still, the eco-friendliness of FFVs is, at best, unclear.

Fuel efficiency is another thing altogether. As with all things related to mileage, there's a lot of variability here, but mileage per tank drops between 15 percent and 30 percent when you switch to ethanol. And because ethanol fuels are generally about the same price as gas, you might actually spend significantly more money -- perhaps hundreds of dollars per year -- to get around on just ethanol.

Considering these facts, you may wonder why anyone would build or buy FFVs. In the United States, federal Corporate Average Fuel Economy (CAFÉ) standards dictate that auto makers must offer vehicles with a minimum gas mileage of 27.5 mpg (22.2 for light trucks); otherwise, they face stiff fines.

There's a loophole, though: If those companies build vehicles that burn ethanol, they won't be fined nearly as much. Basically, it's a government strategy to encourage the use of more ethanol, which effectively subsidizes American crop farmers and could potentially reduce American dependence on foreign oil.

As for the flex engines themselves, well, they're a mature technology that requires zero skills or adaptation on the part of consumers. All you need to do is find one of thousands of gas stations that offer E85 fuel, and your flex engine will take you as far as you want to go -- just not quite as far as it would if you filled up with gas.

FFVs and E85 are getting more and more common, so the pros and cons of the ethanol business model are being played out in the real world for everyone to witness. Corn growers love FFVs because they create greater demand (and higher prices) for their product. And some environmental lobbyists see E85 as a stepping stone to cleaner-burning fuel sources. But whether ethanol can make a serious, long-term dent in our dependence on foreign oil remains to be seen.

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