Aug 04 2010
Stop-start restart: GM mild hybrids return in ’11
General Motors Co. plans to bring back mild hybrids next year, said Larry Nitz, GM executive director of hybrid and electric powertrain engineering.
GM discontinued mild hybrids after 2009 when the closing of Saturn left the carmaker with the technology on just one vehicle, the Chevrolet Malibu sedan, Nitz said. It had been available on the Saturn Vue crossover and Saturn Aura sedan as well.
Nitz, who spoke on the sidelines of the seminars here yesterday, said a new, more powerful system will be available in the third quarter of 2011 on at least one mid-sized sedan in North America and one in China.
He declined to name the vehicles, but he said the first-generation mild hybrid system was available in China on the Buick LaCrosse. He wouldn’t discuss the price of the option.
Unlike a full hybrid system, a mild hybrid system cannot propel a vehicle on electric power alone. It acts as a stop-start system, shutting off the gasoline engine when the car stops and then using the batteries to restart the engine when the accelerator is pressed again.
The motor also provides a boost during acceleration.
Nitz also said GM intends to make some of its own electric motors for hybrids instead of buying them all from suppliers.
He said the first GM-made electric motors will be produced in its White Marsh powertrain plant near Baltimore. He said they will be used on the next-generation Two-Mode hybrid technology, which will be an option on future pickups and SUVs.
Nitz called electric motors a core powertrain competency that GM must design and fully understand so it can integrate them into hybrids and plug-in electrics for peak fuel economy and performance.
He declined to reveal when the next-generation Two-Mode hybrids would be introduced. With a Two-Mode, a driver benefits at highway speeds from the electric motor, not just predominantly at starts and stops.
Nitz said GM will reintroduce mild hybrids on its mid-sized sedans with improved technology. They will offer about 20 percent better fuel economy than gasoline engines, he said.
Nitz said the electric motor is improved and the electronics and controllers are fully integrated with the conventional gasoline engine. The system will be wedded to GM’s Ecotech engine and a six-speed transmission capable of maximizing performance and fuel savings, he said.
When the mild hybrid was introduced in the Saturn Vue in 2006, it was bolted onto a four-cylinder engine and four-speed transmission not designed for regenerative braking. That mild hybrid produced a 15 percent improvement in fuel economy.
