Master of Cylinders - 20 Years Later

Jonathan Fahey submitted this story for Forbes:

"After 20 years of hibernation, engines that can shift on the fly from eight cylinders to four and back again are rumbling awake.

On a recent ten-minute drive near a General Motors site in the stop-and-go suburbs of Pontiac, Mich., a prototype pickup truck switched from eight cylinders to four cylinders and back again--32 times. No one onboard noticed a thing.

The truck held a new V-8 engine that shuts down four cylinders on the fly whenever they aren't needed. The aim: to improve fuel economy without sacrificing brawn. These engines boost gas mileage up to 25%, the equivalent of trimming 1,500 pounds of steel off a 4,000-pound truck.

Americans love their SUVs and pickups, but most times they drive them as if they were cars; the monsters pack far more power than they use. With the new engine, "You can still pull your 14,000-pound Airstream if you want to," says Samuel Winegarden, GM's chief engineer on the project. "But many, many people in this country drive their SUVs and trucks around not heavily loaded."

GM tried this 20 years ago in Cadillacs, with embarrassing results. The car's computer wasn't sufficiently powerful to adjust the engine timing precisely enough to make the switch seamlessly. "All that bumping and banging and clanging was not what customers were looking for, particularly in a Cadillac," Winegarden says. The option was dropped after 18 months.

The mechanical control that shuts off cylinders has changed little from the 1981 version, but now the computer--equivalent to an early 1990s Macintosh--runs at 50 times the processing speed and holds 100 times the memory. Mercedes-Benz uses a similar system in its $118,000 S600 sedan. GM will put the engines into more prosaic, higher-volume vehicles. About 100,000 midsize trucks will get the engines in 2004. By 2007 GM plans to sell up to 2 million copies a year. The only clanging GM hopes to hear would come from its cash register: The new engines will cost no more to build than the current ones.