Engineers Grapple with Power Demands

Power to the People: Chrysler is using BlueConnect, based on Bluetooth, to bring telematics to consumers and prompting engineers to find ways to save power.

Power consumption is an important factor for any system that uses a battery, but automobiles have been immune given their ability to recharge their batteries quickly.

But automotive engineers are now beginning to look more closely at the impact that electronic products have on the intertwined issues of fuel economy and emissions.

After more than two decades, conventional electronic emissions control units have been fine tuned so much that further refinements don't yield much. To meet tighter clean air regulations, design engineers are now reducing the load on the alternator. "We have to manage the electronic load. Electronics are not powered for free," says Nick Zielinski, director of Vehicle and Technology Integration at General Motors' Warren, MI, facility.

One technology that's currently moving from development labs to the highway is fuel-on-demand. Currently, electronic fuel pumps run at a constant speed, and any fuel that isn't injected is recirculated back to the gas tank.

Fuel-on-demand systems pull only the necessary amount of fuel, so the fuel pump can run at lower current. A microprocessor will monitor the speed and acceleration, as well as input from temperature and pressure sensors, to determine how much fuel is necessary given the current driving conditions. The fuel pump will then draw only the necessary amount of fuel.

"We're looking at places that have a constant current draw. If we can regulate that, we can improve mileage," Zielinski says. "We aren't talking about huge amounts, not on the order of 2 mpg, but if we collect a bunch of things together, it adds up."

There are many new technologies that will push demand for power even further. GPS and navigation systems, as well as telematic products, are expanding rapidly. That's prompted a huge effort to develop higher voltage techniques. Most observers feel 42V systems will meet long-term demands, but the acceptance of 42 V technologies has been slowed by economics.

Reducing power consumption can help delay the costly move to 42V systems, which many say will be necessary to drive the increasing number of electronic features on a vehicle. Zielinski says that some new functions require more power than a conventional 12V system can deliver, so they can only be used on smaller vehicles.

For example, electronic power steering replaces hefty hydraulic systems. The electronic motor draws power only when the driver steers, so it's often in standby mode, drawing negligible power.

It's currently being used on the Saturn View, a fairly light car. But on larger, heavier vehicles, the electronic motors need more power than a 12V system can reliably supply when many other electronic systems are in use. "For electronic power steering, the Pontiac Grand Prix is the cutoff. Heavier vehicles than that need a 42V system," Zielinski says.