November 2002

Why Not a 40-MPG SUV?

Continued from page 2

By Mark Fischetti

Souped Up Software

New equipment such as powerful starter-generators would raise fuel efficiency. Yet a vehicle could achieve even greater gains if the entire power train were controlled electronically.

Each component could be adjusted continuously to consume the least power necessary as driving conditions change and-equally important-could be controlled in an integrated way for systemwide savings. "Fuel efficiency would be even greater than the sum of the components," says Frank Lohrenz, an electrical engineer at Siemens VDO Automotive in Regensburg, Germany.

The savings could be significant. Integrated software-control systems could provide a 10 percent fuel-efficiency boost (see "The Networked Car," TR September 2002). Siemens' software, for example, optimizes the delivery of torque-the turning force of the power train. To do this, the system electronically registers how far and how fast the driver pushes the gas pedal. Then through electronic control of such basic mechanical components as the engine, transmission, and a future starter-generator, it delivers the requested torque. The Siemens' technology takes into account 20 parameters-including vehicle speed, engine rotation speed, and transmission gear-before deciding how best to deliver torque from the combined efforts of engine throttling, transmission gear ratio, and starter-generator activation.

Engineers have traditionally considered each component as a stand-alone unit, but there is plenty of interest in integrated control because it's cheap: integrated control depends largely on software, and thus, its 10 percent fuel-efficiency boost comes at relatively low cost. "If a manufacturer sells one million cars," Lohrenz says, "the cost could be less than $5 per vehicle."