Green Tuning

Here's an outtake from a piece I wrote for the New York Times about hacking a car's computer to make the car run faster, cleaner, or both.

MOST modifications are done to speed cars up, not clean them up. But hacks can also improve fuel efficiency for many cars, especially gas-electric hybrids like the Toyota Prius.

Hybrids are gas-powered vehicles that save fuel by extending their internal-combustion engines with electric motors. Onboard computers regulate the interplay of gas and electric power. The electric motor provides some or all of the start-up power at low speeds, for example, when using a gas engine would be inefficient. Electric motors also provide a boost for acceleration. And during deceleration, they function as generators, converting much of the car’s momentum into electricity to recharge the batteries.

But the electric motors can do a lot more, say advocates of so-called “plug-in” hybrids like the California Cars Initiative, or CalCars. By carrying additional batteries, which are plugged in to a wall socket for overnight charging, hybrids can make greater use of the electric motor. In some conditions, they can run solely on electricity for up to a few dozen miles (enough for many commutes and local errands). Electricity is a cheaper power source than gasoline. And pulling power from the grid, instead of from a gas engine, generates only about half as much carbon dioxide per mile, said Felix Kramer, the founder of CalCars.

In the fall of 2004, CalCars converted a Toyota Prius into a plug-in hybrid by installing extra batteries and modifying the car’s computer settings to recognize the new power source and run the car in electric mode as much as possible. Since then, a few commercial plug-in conversion services have emerged. A company called Hymotion, for example, plans to start offering conversions for the Toyota Prius by the end of the year. Prices are high, however: at  $9,500.

CalCars is lobbying hybrid makers like Ford and Toyota to build cars with plug-in abilities, which it estimates would add about $3,000 to the sticker price. “It’s the same as buying an extra feature like leather seats,” Mr. Kramer said. “Millions of people want to buy that environmental feature.” Meanwhile, CalCars is developing a program to help late-model Prius owners do their own plug-in conversions. Technical assistance is free; parts are about $3,000.