eAssist technology extends Malibu ECO driving range to 550 miles


With the debut of the 2013 Chevrolet Malibu in New York and Shanghai auto shows, General Motors not only continues to leverage its Global Epsilon D-segment architecture, but its eAssist™ technology as well. This option extends the driving range of the Chevy Malibu ECO to 550 miles.

The photo shows the General Motors (NYSE: GM) display of eAssist™ at the SAE 2011 World Congress in Detroit. This is considered a mild form of vehicle electrification when compared to the Chevrolet Volt and other full hybrids.

Originally introduced for the Buick, the eAssist technology for the Malibu ECO is basically the same stop-start system. The Malibu ECO combines it with a 180-hp (134-kW) direct-injected 2.4-L Ecotec four, 6T40 6-speed automatic transaxle, Hitachi-supplied 115-V air-cooled lithium-ion battery pack, and belt-driven motor/generator.

According to Chevrolet media sources as well as an article by EV.SAE.org, the system is capable of producing approximately 11 kW (15 hp) of electric power assist during hard acceleration and 15 kW (20 hp) of regenerative braking power.

The liquid-cooled, induction-type motor/generator unit delivers 79 lb·ft (107 N·m) and provides electric-only operation at very low speeds. For the record, the motor/generator is supplied by Continental, a major supplier to the auto industry with a design center located north of Detroit..

The battery pack for the system has a total package mass of 65 lb (29 kg); and is located in the trunk behind the rear seat. It includes an integrated power inverter along with a 12-Volt power supply. The pack has a peak power density of 518 W/kg.

According to Steve Poulos, System Chief Engineer quoted by the EV.SAE.org article, the battery has a working state-of-charge (SOC) window of approximately 20%.

And like other lithium-ion battery systems, this one requires cooling; but instead of a liquid, a small electric fan draws air from the cabin.

The electrified power system, as it is called in some engineering circles, enables the internal-combustion engine to literally shut down fuel delivery in certain deceleration conditions. The eAssist is thus officially deemed by engineers as a mild hybrid technology.

Used in the Chevrolet Malibu Eco, the drive function is reported to be transparent; in other words, the driver does not realize that the vehicle is operating with an electric power boost at all. The biggest difference between the Malibu Eco and the standard Malibu, though, will definitely be the silence from the engine compartment when the vehicle is sitting at a stop light.

The Malibu Eco will excel in highway mileage when compared to the Toyota Camry and Nissan Altima hybrid at 35 mpg, and the Ford Fusion hybrid at 36 mpg. Chevy expects 38 mpg highway. However, those vehicles are considered full hybrids which perform best for city mileage, at 31 mpg and 41 mpg, respectively, whereby the Malibu ECO is rated well below at 26 mpg. The reason for this difference centers on the design choice of the final drive ratio.

As with the Buick LaCrosse, the eAssist for the Malibu ECO enables a numerically lower final drive ratio. GM engineers claim it gives the Malibu ECO up to 550 mi (885 km) in range with the 15.8-gal (60-L) fuel tank.

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