American cars will soon get 'start-stop' fuel-saving tech

With new technology from Mazda and BMW, cars won't just idle at stoplights -- they'll shut off entirely.

For a buzzy new technology, "start-stop" systems are unusually simple: When an equipped car stops, so does its engine. When a brake pedal is released, or an accelerator pedal depressed, said engine kicks back to life.

Companies like BMW and Mazda are already building this technology into cars sold in European markets, but the Detroit News reports that start-stop engines are coming stateside--and soon.

The concept may sound familiar to drivers of hybrid cars, which favor their inbuilt electric motors during stops and low-speed acceleration. That said, the idea is still a novel one for traditional, gas-powered cars, especially in the U.S. And while experts peg the fuel-saving potential of such systems at up to 15 percent, the road to domestic acceptance winds up a pretty steep hill.

One key to selling the American public on this feature -- which will often be included as a paid, premium option -- will be the ability to advertise its effectiveness.

For now, this will be tough: The EPA's test for city mileage only includes one extended stop, which means official fuel efficiency ratings -- the only figures American automakers are allowed to advertise to the public -- will barely reflect start-stop systems' advantages.

Then there's the issue of maturity. British car site, though hardly known for its green advocacy, lodged some fair criticisms against i-stop, Mazda's start-stop system:

If you want to run the aircon or wipers or de-misters, it’ll only switch off for a few seconds or sometimes not at all. Despite having a second battery to run the starter motor, i-stop is reluctant to do its thing unless you switch everything off. We tested the car in 25° (77° Fahrenheit) heat, selecting a 20° (68° Fahrenheit) cabin temp, and it could only manage about four seconds before calling on the engine again.

Beyond that, automakers face technical obstacles in incorporating stop-star systems into cars with automatic transmissions, which are far more dominant in the U.S. than most of the rest of the world. (The first American start-stop car, coming as early as next year from BMW, is purported to have an automatic transmission.)

One thing start-stop transmissions do have working in their favor is subtlety. They don't require any action on the driver's part, nor do they dramatically change the core driving experience, though sudden engine shut-offs can be jarring to first-time users.

In any case, with stringent EPA regulations looming on the horizon, and perpetual fears of rising energy costs, the answer to the most obvious question facing stop-start systems -- why? -- should be easy enough to answer.

Perhaps the more pertinent question, and certainly the one automakers would like their customers to be asking, is: why not?

Photo: BMW

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