GM has high hopes for hybrid system
Several things about the announcement are significant, including the venue itself. Symbolic in the choice of what is perhaps the world's most "international" auto show is the fact that, unlike GM's current practice, these new hybrids will be sold in multiple markets outside North America.
Indeed, the system made its debut in a Saab 9-X Bio-Hybrid concept car.
Other significant points include the use of lithium-ion batteries (still a stumbling block in the implementation of the company's E-Flex technology), the potential for mating the system to smaller, turbocharged engines in a mutually complementary way, and GM's forecast of high volume production – more than 100,000 per year.
The architecture of the next-generation system is familiar. It's essentially a more robust interpretation of the BAS (Belt Alternator Starter) technology now used in the Chevrolet Malibu, Saturn Aura and Vue Green Line hybrids.
To refresh your memory, the core of the BAS system is a motor-generator that replaces the conventional alternator. It connects mechanically to the engine via a beefed-up drive belt, just like the alternator.
In other ways, the system layout, including the use of battery pack, power transformer and electronic control unit, is similar to that of other hybrids. But mounting the motor-generator externally to the engine enables significant cost savings.
The next-generation motor drive is three times more powerful than the current version. That added power not only gives the internal combustion engine extra boost when passing or hill-climbing, it also means the vehicle will run to a slightly higher speed on electric power only on takeoff, although that capability is used mainly to start the engine. Unlike more sophisticated hybrid systems, which can operate for a continuous period on electric power alone, that ability is very limited with the BAS system.
Nevertheless, GM chairman Rick Wagoner says the next-generation GM hybrid system will reduce fuel consumption, on a directly comparable basis, by about 20 per cent.
But GM has another trick up its sleeve as well: combining the new hybrid system with a smaller (1.4- or 1.6-litre vs. 2.0- or 2.4-litre) turbocharged engine.
The characteristics of the electric motor booster – high torque at low speeds – directly offset the inherent tip-in lag of a turbocharger.
Conversely, when the electric motor figuratively runs out of steam at higher speeds, the turbocharger provides the boost to maintain the performance level of a larger engine.
And the whole package operates with an even further improvement in fuel efficiency and correspondingly reduced CO2 emissions. That would seem like an ideal combination.
The lithium-ion battery pack plays a role in the system's overall efficiency in that it is both smaller and lighter for a given power level than the nickel-metal-hydride batteries it replaces.
The feasibility challenges that lithium-ion faces for use in the plug-in E-Flex application don't apply in this case, GM explains. Here, the need is for high power output for short periods, something lithium-ion excels at.
In the plug-in case, it is for high energy output over a longer period, which requires some fundamental re-engineering of the battery.
While not as technically sophisticated or exciting as other hybrid systems, this is probably the lowest-cost means of hybridization in current use, with many of the advantages realized by much more costly designs.
Accordingly, it stands a good chance of finding enough market acceptance to justify that 100,000-unit forecast.
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