DETROIT – It’s not the first time a supplier or auto maker has predicted broader applications for fuel-saving stop/start technology, but this time around the forecast is for real, say executives at Denso Corp., Asia’s No.1 supplier.

The technology, which shuts off the engine when a vehicle comes to a stop and restarts it when the accelerator pedal is depressed, already is enormously popular in Europe.

Johnson Controls Inc., at the North American International Auto Show last week, predicted the technology is on pace to appear in 70% of all new vehicles in Europe.

In the U.S., the take rate for stop/start has been limited to applications in hybrid-electric vehicles, although it now is standard on both the Porsche Panamera sedan and Cayenne SUV.

Ford recently announced it will add stop/start technology to all North American vehicles equipped with direct-injection turbocharged EcoBoost engines.

Denso’s Doug Patton predicts “rapid expansion” in the number of vehicles equipped with stop/start in the next three years, saying at the auto show the take rate could go as high as 40%.

“We’re currently working with customers for a North American introduction in 2012-

2013,” says Patton, senior vice president-engineering division at Denso International America. “This will probably be DENSO’s first start/stop technology you see in the North American market.”

This first contract entails a basic system already implemented in Europe known as the Advanced Engagement starter. It’s a heavy-duty starter with more durable brushes and an improved clutch. When it’s energized, the pinion shifts forward, engages with the flywheel and immediately spins.

With this system, the fuel will be cut and the engine will stop. Once the gas pedal is depressed, the starter is re-energized to restart the engine.

The world’s No.1 supplier of starter motors (with about 20% of the global market and 50 years’ experience), Denso says it’s been working on stop/start development since the 1980s.

With the basic AE device, there’s potential for lag when the engine restarts, but Denso has designed two different starters to eliminate that lag.

The Permanently Engaged starter (in production since 2008) offers a simple control strategy but requires modification of the flywheel connecting with the starter’s pinion.

The Tandem Solenoid starter has a more complicated control strategy, but can fit in the same space as a traditional starter. That product is scheduled for production later this year.

These first three options improve fuel efficiency between 3% and 5%.

Denso offers yet another option that boosts potential fuel savings to more than 7% by changing the electrical system to accommodate the repeated on/off cycling of a stop/start system.

The key driver is switching from a standard lead-acid battery to a more efficient power source, such as a lithium-ion battery, to reduce voltage drop.

Patton says an improved power source will provide a more efficient regeneration system, which will further reduce carbon-dioxide emissions.

The outlook for stop/start systems in the U.S. depends on how well they are executed, Patton says.

“How does the customer feel about it? Is he going to feel uncomfortable? Will the engine be shut off too long and will cars get too hot or cold?” he says. “It depends how the customer perceives it.”

The key parameter is to decide how long the engine should be shut off and how quickly it restarts. “You can always restart the engine,” Patton says. “But the other side of it is, that’s your fuel-economy benefit going away.”

Another growing product segment for Denso is gasoline direct injection. The supplier first mass produced GDI components, such as high-pressure pumps and injectors, in 1996 and now is starting production of its third-generation system.

Denso’s first North American GDI application arrives in the U.S. later this year on the Ford Focus, powered by a 2.0L naturally aspirated 4-cyl., as well as the Ford F-150 pickup, with its 3.5L EcoBoost V-6. Denso says the system will help Ford boost fuel efficiency up to 20%.

Initially, Denso will manufacture the solenoid-based injectors and pumps in Japan, but production soon will move to Denso’s fuel-systems plant in Athens, TN.

Patton says Denso has other GDI contracts coming online in the next few years for customers in North America, Japan and elsewhere.

tmurphy@wardsauto.com