Displacement on Demand, a concept introduced in 1981 by General Motors for its Cadillac 4-6-8 V-8, initially failed due to lack of technology. However, with developments in today’s state-of-the-art technology and computing power, GM will recycle and implement the concept in its 2005 Chevrolet TrailBlazer EXT, GMC Envoy XL, and GMC Envoy SUV.

How the Technology Works
The purpose of Displacement of Demand is to maximize fuel economy without affecting the vehicle’s performance and ability to carry loads, while minimizing harm to the environment. Large trucks and SUVs equipped with Vortec V-8 engines featuring Displacement on Demand engines begin driving on eight cylinders. Once the vehicle reaches top speed, half the engine shuts down, smoothly transferring operation to four cylinders. The transition is so subtle that only an indicator light informs the driver that half the engine is turned off.

When carrying a light load, the system automatically closes both intake and exhaust valves for half the cylinders, cutting air and fuel supply without compromising speed. To accelerate normally or carry heavy loads, the valves reopen and operate on all cylinders.

Once the vehicle is moving, less power is required for operation. The vehicle effectively runs on half the engine, increasing fuel economy by 8-25 percent. If left operating, the engine’s other half only wastes fuel and money and unnecessarily contributes to air pollution.

“Because there is no degradation in emissions, Displacement on Demand technology will improve overall emissions because less fuel is used,” said Sam Winegarden, GM Powertrain chief engineer of Vortec V-8 engines.

“We have figured out a way to make our engines work smarter and deliver top-of-the-line performance with less effort, with less energy. That’s the essence of efficiency,” said Winegarden.

What the Future Holds
GM plans to produce more than 150,000 V-8s with Displacement on Demand in the first year, increasing production over the next several years to nearly 1.5 million in 2007.

By 2006, Displacement on Demand technology will be introduced to V-6 engine mid-sized passenger cars, and by 2008, the system will be featured in more than 2 million V-8 and V-6 engine vehicles.