Why is fuel-saving start/stop technology just arriving in non-hybrid North American vehicles, years after it became available overseas?

Because until now, the market’s overwhelming preference for automatic transmissions has proved problematic, suppliers say.

Ford Motor Co.’s commitment this week to launch the technology herald breakthroughs accommodating automatic step-gear transmissions found in an increasing majority of vehicles on North American roads.

Start/stop systems shut down a vehicle’s engine at full stop. When the driver releases the brake pedal, the engine restarts.

Robert Bosch GmbH, a major supplier of start/stop technology, says problems stemmed from ensuring the restart sequence was fast enough to enable clutch engagement, gear change and clutch release.

So Bosch says its engineers “adjusted” the starter motor, the pinion-engaging mechanism and the engine’s injection system. Modifications also were made to control software.

With a solution in place, expect more auto makers to adopt the fuel-saving technology – already common on hybrid vehicles – as they rush to meet looming federally mandated corporate fuel-economy standards. The National Highway Traffic Safety Admin. estimates a total ’16 model-year penetration of 23%. Beginning in 2011 with ’12-model vehicles, auto makers must take incremental steps leading toward a U.S. corporate average fuel economy of 34.1 mpg (6.9 L/100 km) by ’16.

Each year, federal targets increase about 4% between 2011 and 2016. Factor in regulations limiting carbon dioxide and U.S. fleet fuel-economy requirements rise to 35.5 mpg (6.6 L/100 km) in 2016.

Ford announces this week it will offer start/stop on non-hybrid-electric vehicles in North American beginning in 2012. The rollout would make Ford the first major auto maker to do so in North America.

The auto maker pulled the sheet off its new system on the core-brand Focus ECOnetic during last year’s Frankfurt auto show.

Ford says roughly 90% of its nameplates eventually will get the system, bowing on 4-cyl. engines and gradually migrating to vehicles with V-6 and V-8 engines. Exceptions include vehicles such as the F-Series Super Duty fullsize pickup.

The auto maker says the technology reduces tailpipe emissions to zero while the vehicle is stationary. Fuel economy can benefit by up to 10% in city-cycle driving.

Start/stop is relatively common in Europe and Asia/Pacific countries, where manual transmissions remain popular. In North America, their market is waning.

According to Ward’s data, 93.3% of U.S. ’10 model year passenger cars and light trucks came equipped with an automatic transmission, including continuously variable transmissions. By comparison, 89.9% of ’00 light vehicles were similarly equipped.

Start/stop in North America largely has been relegated to HEVs because their CVTs are more compatible.

Ford’s non-hybrid system features different starter motors and batteries than its hybrid counterpart.

“Many of the same Ford engineers who designed the Auto Start-Stop system used on Ford and Lincoln hybrids are developing the (new) Auto Start-System for non-hybrid vehicles that will be sold around the globe,” Barb Samardzich, Ford vice president-powertrain engineering, says in a statement.

The auto maker does not say whether there will be an additional charge for the system, which eventually will be offered in all of Ford’s global markets.

Hella KGaA Hueck & Co., another supplier of start/stop systems, says they cost a “few hundred dollars” and promise fuel-economy improvement of 10%-15%.

Currently, the Porsche Panamera is the only non-hybrid vehicle sold in North America to feature start/stop technology. The Panamera is equipped with the auto maker’s new dual-clutch gearbox, known as Porsche Doppelkupplungsgetriebe.

Several other auto makers, including Chrysler Group LLC, have announced plans to offer start/stop.