IEEE Spectrum January, 2007 - 31

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engineers figured out they could reliably their flex offerings, and since then, sales a big push toward E85, the 85 percent ethaand accurately calculate the ethanol con- of flex cars have skyrocketed. In 2003, they nol and 15 percent gasoline blend. The same
tent of the fuel using software and existing corresponded to only 3.5 percent of total trend is occurring in a host of other counsensors in the car.
sales; now that share has risen to nearly 90 tries, including the United States, China,
The key component in this approach is percent. Marelli supplies its flex ECUs to India, and Japan.
an oxygen probe that sits at the engine's Brazil's largest automakers, including Fiat,
And don't forget about the TetraFuel's
exhaust manifold. Its function is to sense Ford, and Volkswagen, and it has about ace in the hole: its natural gas capability.
the amount of residual oxygen after com- 50 percent of that market, with the rest Natural gas has historically cost less than
bustion, a measurement that helps the ECU divided between Bosch and Delphi Corp., oil, and reserves are plentiful, so it could
fine-tune the air-fuel mixture. If it detects, in Troy, Mich.
work as another transitional fuel if gasoline
say, too much oxygen in the exhaust, the
"To some extent, what's happening in prices go up. There are already more than
ECU increases the fuel going into the cyl- terms of cars being sold there is fairly 5 million natural-gas vehicles around the
inders. It then checks the oxygen
directly attributable to the capabil- world. Argentina has a fleet of 1.5 million,
level again, repeating the process
ity that Marelli's solution has and Brazil and Pakistan have more than
every few milliseconds until the
provided," says Sharfman, the 1 million each. Other countries investing
mixture is precisely adjusted to
auto expert in New York City. in natural-gas cars include Iran, which
Tell us
the stoichiometric ratio.
"So if you started to have an has the world's second-largest natural
which technologies
A M a rel l i tea m led by
efficient source [of ethanol] gas reserve; Germany, which plans to
will sink or swim,
at www.spectrum.
Fernando Damasceno, a specialhere or in some other country, have more than 1000 natural-gas fillieee.org
ist in ethanol-powered engines,
I think that over time this kind ing stations by the end of the year;
realized they could exploit that
of solution is going to spread." and France, which has a prog ram to
same feedback loop to determine,
let drivers fill up their natural-gas cars
indirectly, the ethanol percentage in the fLEx-fuEL TECHNOLOGy HAS succeeded using home refueling units.
fuel mix. Here's how: let's say you are run- in Brazil mainly because consumers saw
Marelli is discussing with other autoning on pure gasoline. If you hit the gas a chance to save money. Because ethanol makers the use of the technology outside
pedal and add air to the fuel mix going into comes from an agricultural product, its Brazil, but the company declines to provide
the cylinders, the ECU easily calculates price varies according to crop seasons. In any details. Could the TetraFuel become
the amount of fuel needed to keep things October 2006 in southeast Brazil, gasoline a hit in Europe, Asia, or North America?
"happy," that is, to reach the stoichiometric cost an average of $1.12 per liter and ethanol Time will tell.
ratio. Now suppose there's some ethanol, was $0.63. You'll go farther on 1 L of gasoline,
In the meantime, flex technology and
in addition to gasoline, in the tank. The but in the end the cost per kilometer is still ethanol could make energy production
ethanol-whose energy density is less than less with ethanol. At 1000 km (621 miles) more regionalized, with countries progasoline's-reduces the stoichiometric per month, flex fuel could save the average ducing biofuels where there's arable land
air-to-fuel ratio of the mixture, and that driver around $200 per year.
and favorable weather. Different fuels
means you need more fuel in proportion
"The Siena TetraFuel advances this would be available in different places,
to air to burn both completely.
flexibility one step further," says Marco and drivers wouldn't have to worry
But if the ECU doesn't know how much Antonio Saltini, director of government about it. "The idea is to have a multiethanol is in the tank, how does it know relations at Fiat in Brazil. "Consumers fuel car that runs with the fuel it finds,"
what the new stoichiometric ratio is? It see a chance to save even more using Bonfiglioli says.
doesn't, initially. The ECU keeps increas- natural gas."
"You can't yet put water in," he jokes.
ing the amount of fuel injected while it
Running on natural gas, whose cost "But just wait."
-Erico Guizzo
monitors the oxygen probe at the exhaust. per kilometer in Brazil is less than half
It knows when the stoichiometric ratio has that of gasoline, someone who drives more
been reached when it determines there is than 160 km per day can recover the addino oxygen there. The ECU records the fuel tional cost of the TetraFuel system in nine
T.J. RODGERS: Hitler's Mercedes
increment and compares it to values stored months to a year, saving some $1095 annuran on either diesel or gasoline.
in its memory, and in that way it finds that ally, Saltini says. He adds that implementthe mixture is, say, 90 percent gasoline and ing a natural gas system by retrofitting
Where's the innovation?....Electric
10 percent ethanol. Each time fuel is added would cost twice as much as doing the
cars can already run on about
to the tank, the ECU repeats the process.
same with the TetraFuel system.
one-third of the cost of gasoline and
Marelli's sensorless approach seemed
Still, it's a niche market. Fiat hopes
with much less pollution.
promising, but still the company got to sell around 2500 Siena TetraFuel cars,
nowhere with automakers. "They said it currently priced at $19 124 each, this year.
GORDON BELL:
wouldn't work," Bonfiglioli recalls. "We It's a tiny fraction of the more than half a
had to show them our demonstration million vehicles that Fiat's Brazilian unit This is just nice engineering. If
vehicles." That was in 2000. It was only sold in 2005. But Saltini notes that because Toyota converts a Prius to this,
three years later that Volkswagen, in the car can run on pure gasoline, Fiat can you'd get a fifth power source.
Wolfsburg, Germany, decided to give it a sell it elsewhere in Latin America. In fact,
shot. In March 2003, using Marelli's flex- the automaker says the Siena TetraFuel
NICK TREDENNICK: It seems the
fuel system, the automaker introduced the should hit the Argentinean market early
option for natural gas has a high
Gol TotalFlex, the first flex car in Brazil.
this year.
cost in extra hardware-plumbing,
That launch, combined with the
The TetraFuel technology has interestBrazilian government's decision to give ing possibilities in other markets as well.
tanks, and engine-and in loss of
flex cars a tax break, spurred a revolu- The European Union plans to increase
trunk space.
tion in the country's automotive industry. the share of biofuels in transportation to
Other big automakers rushed to announce 5.75 percent by 2010, and many experts see

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Table of Contents for the Digital Edition of IEEE Spectrum January, 2007