Last year GM discontinued several mild hybrid models it was offering, including the Chevy Malibu and Saturn Aura hybrids. These systems relied on a stop-start belt-alternator system that improved fuel economy about 10%. Those cars used small 36-v nickel metal hydride batteries and did not have the capability of pure electric propulsion.
The cars were discontinued due to poor sales in the case of the Malibu and the brand’s demise in the case of the Aura.
According to GM’s executive director of hybrids an EVs, Larry Nitz, however, GM will be re-introducing a more powerful second generation of the system next year.
The second generation mild hybrid system uses a larger 100-v lithium-ion battery, regenerative braking, and can provide boost during acceleation. It still cannot drive purely on an elecric motor so in that way is similar to Honda’s IMA system currently in use in the Insight and CR-Z.
Nitz said the application will debut in a mid-size car in the third quarter of 2011 but declined to announce the model. Some experts speculate it could appear in the new Buick Regal.
GM will eventually manufacture its own electric motor for the system as opposed to sourcing it from suppliers as it has in the past. In-house electric motors will first get put to use in the next generation two-mode hybrid system which will appear as an option in future trucks and SUVs. The two-mode system will also have a plugin variant, and are more powerful allowing electric only propulsion and electric assist at both low and high speeds. Nitz declined to say when either would debut
The new mild hybrid design will achieve a 20% efficiency gain over gas engines. In the system, a small electric motor is mated to a 4 cylinder Ecotec engine and a six speed transmission, and the engine will be turned off whenever the opportunity arises. In the first generation system the motor and small battery were bolted to a four cylinder engine and 4 speed transmission which were not optimized for efficiency or regenerative braking.
GM had once considered producing a lightweight highly-aerodynamic dedicated non-plugin hybrid capable of over 50 MPG, but cancelled the program in favor of focusing on the Volt.
Source (Automotive News)








