Cylinder deactivation — tried once by General Motors Corp. in the early 1980s with essentially disastrous results — returns with much more convincing potential, thanks to the sophisticated electronic controls and actuators unavailable when GM experimented with the concept two decades ago.

GM, the most vocal proponent of new-age cylinder-deactivation technology, which it dubs Displacement on Demand (DOD), says it will deliver a fuel-economy improvement of around 6% to 8% for engines so-equipped.

But now GM appears to be in a race to market with Chrysler Group, which recently announced that its '05 Chrysler 300 Series and Dodge Magnum rear-drive vehicles will offer its 5.7L Hemi Magnum OHV V-8 with a cylinder-deactivation system it calls Multi-Displacement System (MDS).

Chrysler's MDS-equipped cars will begin arriving in dealerships this spring. GM sources say its first vehicles with DOD-equipped 5.3L OHV V-8s are coming in late summer.

Honda Motor Co. Ltd. also will launch this year a new overhead-cam V-6 with Variable Cylinder Management (VCM), shutting down three of the engine's six cylinders when not needed, as part of a hybrid-electric drivetrain for Accord.