General Motors may aim to make hydrogen-powered fuel cells the powertrain of the future, but this decade the automaker is taking many steps to improve the internal-combustion engine.
The technology will be crucial to boost GM's corporate average fuel economy in the next four years. The programs rely on cylinder deactivation, full hybrid powertrains and limited hybrid systems that save fuel by automatically turning the engine off under most idle conditions.
Hybrids use electric engines to supplement internal-combustion engines during starting, acceleration and other times when they are least efficient, improving fuel economy.
GM will launch a limited hybrid system, marketed as Hybrid FlexPower, as an option on the 2004 Chevrolet Silverado and GMC Sierra pickups. GM claims a 10 percent to 15 percent increase in fuel economy and a reduction in emissions.
"The strategy here is to go after the highest fuel-consuming vehicles first," says Tom Stephens, group vice president of GM Powertrain.
The system replaces a standard starter motor and alternator with a 14-kilowatt electroinduction motor, or starter-generator, in a 42-volt electrical system.
For example, Hybrid FlexPower automatically turns off the engine at a traffic light. The engine restarts quickly when the accelerator is depressed.
GM plans a full hybrid Saturn Vue for the 2006 model year, with a 300-volt electric motor to assist the gasoline engine when accelerating.
Another limited hybrid system, using a belt-alternator starter, debuts on the 2007 Chevrolet Equinox and 2007 Chevrolet Malibu. The system, like the Hybrid FlexPower, reduces power during deceleration, turns off the engine at stops and restarts the motor when the driver hits the accelerator.
It will be available initially on GM's most common four-cylinder engine, called the Ecotec. When used in combination with a continuously variable transmission, the system is expected to increase fuel economy 12 percent to 15 percent. Ecotec is powered by a 36-volt battery and a conventional 12-volt battery.
GM's cylinder deactivation system, marketed as Displacement on Demand, moves into some product lines in the 2005 model year: the GMC Envoy XL, Envoy XUV and Chevrolet TrailBlazer.
In most driving situations, fuel is provided to half an engine's cylinders. But during acceleration or under a heavy load, all cylinders receive fuel, providing power. GM says the system will provide an 8 percent increase in fuel economy.
Eventually, some V-6s and most of GM truck V-8s will use the cylinder deactivation system.