"Dual-Displacement" Engine

by Illustration courtesy of Ford Ford's Variable Displacement Engine: A sophisticated system controls monitors.
1. Dual Electronic Throttle Control for smooth torque-controlled mode transitions. 2. Dual Intake System for good sound quality from the engine in both activated and deactivated modes. 3. Acoustic IMpedance Control Valve to improve overall exhaust sound quality and level. 4. Vibration Cancellation Engine Mounts for reducing vibration and noise at idle and mode transitions. 5. Delatching rocker arm hardware is used to deactivate the valves. Illustration courtesy of Ford

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TIMELINE


January 1977: In 1977, the United States signs a treaty prohibiting international commerce in endangered species; balloon angioplasty is introduced as a treatment for heart disease; Tandy Corp. and Commodore introduce personal computers with built-in monitors; the first linked automated teller machines appear; Roots is broadcast on television.

As you cruise down the freeway, your engine smoothly shifts into fuel-saving mode, temporarily shutting down half its cylinders. The adjustment is almost transparent. When you need power, a computer control reawakens those sleeping cylinders, again almost imperceptibly.

As we reported in 1977, automakers have long sought an engine that on occasion hoards power in return for fuel efficiency. In the scenario described above, however, the word that has proved most elusive for automotive engineers is smoothly.

Heralding the arrival of this "dual-displacement" technology, we reported that a Ford 300-cubic-inch, six-cylinder truck engine would be equipped with computer controls that would disable half of those cylinders under certain conditions to save fuel.

Today, the technology remains challenging and its promise largely unfulfilled. We spoke with Ford's recently retired James R. Clarke, who was in charge of the original project. Clarke cited as key hurdles rudimentary computer controls, low power-to-weight ratios, and difficulties in controlling vibration when the engine switched to half power.

Ford is continuing to pursue the elusive goal, says Ford senior technical specialist Chinu Bhavsar. Computer controls are more sophisticated, he says, and new "active engine mounting" is smoothing out the vibration difficulties. Noise-control technology is doing the same with exhaust noise. Ford isn't ready to say when we'll see dual-displacement in a production vehicle, only that it will be soon.

Among other carmakers, General Motors is planning to begin equipping large trucks and sport-utility vehicles with displacement-on-demand engines by 2004.