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New hybrid system on Ford C-Max hybrid and plug-in will be cheaper, but better?

Consumer Reports News: November 03, 2011 03:38 PM

Ford released a few more details about its upcoming C-Max hybrid and plug-in hybrid vans on a conference call with the Electric Drive Transportation Association (EDTA) this week.

Nancy Gioia, the company’s director of advanced-powertrains, revealed that the C-Max will use Ford’s “next-generation” hybrid system. She said the new system will have greater efficiency that the one used in the Ford Fusion Hybrid, a higher top electric speed than the Fusion’s 47 mph and will cost 30 percent less.

In our experience with recent hybrids, we’ve found that not all are created equal. Toyota’s hybrid system is also used in current Ford hybrids. It uses two electric motors -- one as a generator and one to drive the car. In between, and linked to the gas engine is a planetary gearset (called a "torque-split device") that acts as a continuously variable transmission and mixes or diverts power between the gas engine and the electric motor. We have found this system works very well to improve fuel economy, it has proved very reliable in our Annual Auto Survey, and it performs unobtrusively.

More recent full-hybrid designs such as the Hyundai Sonata Hybrid and Infiniti M35h use a single electric motor sandwiched between two clutches between the engine and a conventional automatic transmission. While some of these hybrids deliver a significant fuel economy improvement over their conventional counterparts, they can’t match the smoothness or fuel economy of torque-split hybrids. In fact, the Sonata and M35h hybrids were so rough that we’d never recommend them over their conventional counterparts.

Honda uses an even cheaper hybrid system, which bolts the electric motor directly to the engine and uses a clutch to mate the setup to a traditional continuously variable transmission. It uses variable valve timing to cut off fuel flow to the engine at low speeds, but the engine only stops at idle. This system has also proven reliable in our Annual Auto Survey, but it doesn’t deliver the fuel economy benefits of torque-split transmissions. And the system offers little potential for developing plug-in hybrid models.

We’ve found that the cheapest hybrid systems often bring the most compromises and are least effective at saving gas. If Ford is cutting the cost of its “next-generation” hybrid system by 30 percent, we hope it isn’t also reducing its refinement and functionality on the C-Max and C-Max Energi.

Eric Evarts

   

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