Stop-start shuts down a vehicle's engine when the motorist comes to a full halt at a stoplight. The moment the driver lifts his foot off the brake, the engine restarts.
Currently, Ford's hybrid-powered Escape and Fusion feature stop-start. Stop-start also is available in a number of European-built models such as the Porsche Cayenne and Panamera, Fiat 500, Volkswagen Passat and Golf, among others.
Now pressure to meet the EPA's 35.5 mpg CAFE standard for the 2016 model year is driving other automakers to adopt this technology, says Jeff Jowett, manager of North American powertrain forecasting for IHS Automotive, a consulting firm in a Detroit suburb.
Stop-start's North American installation rate will rise from nearly zero last year to 13 percent in 2015, Jowett predicts. In Europe, stop-start's market share is likely to rise from 18 percent today to 65 percent in five years.
"You'll start to see this technology from all the automakers," Jowett said.
Some suppliers are even more optimistic. Robert Bosch GmbH, which produces several components used in stop-start systems, predicts the North American adoption rate could hit 50 percent in 2016.
"There are many more applications coming," said Frank Frister, program manager of Bosch's North American starter division.
Bosch and Denso International, both of which supply engine components to Ford, are positioned to profit from the trend.
Stop-start systems require new software for the engine control unit, a beefed-up battery, a more durable starter, various sensors, plus an electric auxiliary water pump. Gasoline direct injection is a nice complement, too.
Ford's system generates fuel savings of 4 to 10 percent, depending on driving conditions.
"We're building off our experience with the hybrid vehicles," said Birgit Sorgenfrei, Ford's stop-start engineering leader. "We carried that know-how through the system."
But Ford could not simply bolt its existing hybrid stop-start system onto conventional gasoline powertrains, Sorgenfrei says.
To allow seamless engine restarts, the automaker developed software for its engine control unit.
Ford also is pairing stop-start with gasoline direct injection, which permits quicker engine restarts because it sprays fuel directly into the cylinder head. Denso International supplies fuel systems for Ford's direct gasoline injection.
Since stop-start systems increase wear on the battery and starter, Ford beefed up both components. The automaker will use a more durable 12-volt lead acid battery purchased from Johnson Controls.
Ford also has redesigned its auxiliary water pump, a component that normally is belt-powered by the engine. A new electric pump supplied by Bosch channels heat to the passenger compartment while the engine is stopped.
Perhaps most important is the engine control unit, which required reprogramming for smooth transitions between stops and starts.
Ford is still working out a few loose ends. The company is developing a beefed-up starter, and it also must tweak its automatic transmissions to permit quicker restarts.
Ford is expected to put stop-start technology on the Ford Focus and the new C-Max due in U.S. showrooms late this year. Then Ford will migrate the technology to its V-6 and V-8 powertrains.
How quickly will this technology spread? Most automakers haven't gone public with their plans for stop-start in North America. But Jowett of IHS Automotive believes the technology could catch on quickly.
Whenever possible, automakers would prefer to use the same powertrains in Europe and North America, Jowett notes.
That's why the technology could catch on even more quickly than IHS expects. "My gut feeling tells me that our forecast may be too low," Jowett says. "We are adding more vehicles to our forecast."