The drumbeat of idling engines at stoplights is starting to be replaced by silence, the result of an engine technology expected to spread fast within a few years
"Start-stop" is a gas-saving system that shuts off the engine when the car is stopped for more than a few seconds, then restarts it, in most systems, when the driver releases the brake.
Though common in gas-electric hybrids, it's just now coming to conventional vehicles. It requires some tricky electronic controls, but it otherwise requires only a beefed-up battery and starter and a few other parts.
The subcompact Kia Rio, the most inexpensive car in the South Korean maker's lineup, has start-stop on the redesigned 2012 due in showrooms next month. Kia joins luxury brands such as BMW and Porsche, which have it on several new models. On Monday, Kia announced Rio's starting price of $14,350 with shipping.
"It's going to be very popular," says John O'Dell, a senior editor for auto research site Edmunds.com. He thinks it will show up on more than half of all models within five years. "It's a fairly inexpensive way to get a 3% to 5% fuel-economy increase."
Automakers are racing to find the most cost-effective technology to raise their average fuel economy to the required 35.5 miles per gallon by 2016, up from about 27 mpg today.
With only about six parts, start-stop was a fairly simple addition to save gas in the Rio, says Kia product planner Steve Kosowski. He says Rio owners will gain, even though the benefits aren't reflected in the window-sticker mileage rating because of how the Environmental Protection Agency now conducts its tests.
Thus, the Rio is rated at 30 mpg city, 40 highway -- the same as its sibling 2012 Hyundai Accent, which doesn't have stop-start. Automakers are lobbying for testing that better counts start-stop, as in Europe.
Others leading the way:
•BMW. After using start-stop on its M3 performance car, BMW is adding it to its Z4 sDrive 28i sports car and 5 Series sedans, among its best sellers. Start-stop comes with the manual or automatic transmission or both, depending on the model. "We think it could have some gas-mileage gains in normal, everyday driving," spokesman Dave Buchko says. "We're looking at any and all avenues, trying to find any fuel savings that we can."
•Porsche. Now on the Cayenne crossover and Panamera sedan, it's coming to the new 911 sports car. In Porsches, the feature can be turned on or off. Spokesman Nick Twork says start-stop was a key feature in boosting the mileage rating of the new 911 by 15% in European testing compared with the outgoing model.