DETROIT - They won't say how, but Ford engineers have designed a continuously variable transmission for use with higher-torque V-6 engines.
The breakthrough means Ford can coax about 10 percent better fuel economy out of its large front-wheel-drive cars and minivans that use conventional automatic transmissions.
Engineers are developing the CVT in a Ford Taurus with the Duratec 3.0-liter V-6, which generates 200 pounds-feet of torque. Ford let journalists test-drive the car last week.
The transmission also can handle the 225 pounds-feet of torque generated by the optional 3.8-liter V-6 in the Windstar minivan.
That torque capability would cover all fwd cars and minivans in Ford Motor Co.'s lineup, except for the Lincoln Continental and the high-performance Taurus SHO.
BETTER FUEL ECONOMY
Compared to a conventional automatic transmission, which shifts among up to five gear ratios, a CVT uses the entire range of ratios between low and high gears. The CVT does not shift. It achieves better fuel economy than a conventional automatic transmission by constantly changing ratios to keep the engine running in its most efficient rpm range based on driver demands.
The CVT's roots are traced to Dutch company Van Doorne Transmissie BV. In the late 1970s the company invented a metal belt that links two pulleys. Hydraulic pressure makes each pulley wider or narrower, causing the belt to ride higher or lower in the pulley and changing the gear ratio.
Ford's CVT uses a belt made by Van Doorne and a torque converter from an automatic transmission. The torque converter's fluid coupling helps absorb the vibration at starts and stops.
CVT technology has been used in production cars for more than a decade, but its use has been limited to small, four-cylinder engines that do not produce a lot of torque to prevent breaking the transmission belt.
Ford uses CVTs on the Fiesta and the Escort in Europe. Fiat, Lancia, Mercedes-Benz and Nissan also offer CVTs on some European models.
MODELS IN U.S.
In the United States, Honda introduced a CVT on the 1996 Civic HX mated to a 1.6-liter four-cylinder engine with peak torque of 104 pounds-feet. Honda claims that its Civic is the highest-torque production model to offer a CVT. Honda sells between 1,500 and 2,000 CVT-equipped Civics a month, spokesman Art Garner said.
Subaru of America offered the four-wheel-drive Justy equipped with a CVT in the United States from 1988-92, mated to a 1.2-liter, three-cylinder engine that produced 71 pounds-feet of torque.
Ford's top management has not approved replacing its automatic transmissions with CVTs. Engineers also must figure out how to cut the cost of the CVT before considering it for production.
But Ford considers it an important technology to have in case gasoline prices suddenly rise or tougher corporate average fuel economy requirements take effect.