2007 Chevy Impala will be first V6 engine that can switch to three-cylinder operation

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Sure, it's possible to argue about the long-term benefits of ethanol, but GM's announcement that their new 3.9L V6 engine will be a flexible fuel engine is the less exciting of the two bits of news. The second announcement, that the 3.9L V6 will have cylinder deactivation, is really a good idea that is hard to argue with. This is the introduction of cylinder deactivation, called Active Fuel Management (AFM) by GM, in V6 engines. It has been available in V8s for three years.
Cylinder deactivation is an automatic switch from six cylinders to three when the load is light. This means that, for example, on long, flat highway drives, the engine will not burn as much gasoline. The cylinder deactivation feature will see first use in the 3.9L V6 engines used in the 2007 Chevy Impala, whereas the 3.9L V6 with E85 capability will only be available in the Chevy Uplander fleet models. Chevy announced that "Preliminary testing of the 2007 Chevy Impala equipped with the 3.9L V-6 with AFM indicates an estimated 20 mpg in the city and 29 mpg on the highway – improvements of approximately 5.5 percent and 7.5 percent, respectively."

[Source: World Car Fans]

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