For the history-minded, there's a short, interesting article on AutoWeek's website about GM's early difficulties and eventual success with their cylinder deactivation system. The article starts with GM's failed attempt at rolling out their first production engine with the system installed under the Cadillac badge called V8-6-4 in 1981. The system had so many problems that Cadillac dealers often disconnected it because there was no known fix.

Chris Meagher, a GM engineer who worked on the V8-6-4 project, also worked on the successful cylinder deactivation system that was rolled out on 2005 models. He said the problem with the old Cadillac system was three-fold: faulty throttle-body injectors, primitive computerized engine management controls and flawed execution.

Because of GM's unsuccessful history with variable displacement, Tom Stephens, GM's power train chief, approved funding for the new cylinder deactivation project with a disclaimer. He told Meagher that the new system had to transition between eight and four cylinders seamlessly. He said that if drivers could perceive the change, the new system would not make production.

So far, complaints are nonexistent and GM expects to equip 2 million engines with the system at a cost of about $50 per engine annually by 2008.

Despite not reaching production until 2005, Meagher says that GM engineers never gave up on the idea of cylinder deactivation. He adds that one major development in component design significantly helped to bring forth a successful system - supercomputers that enable engineers see how parts work on a screen. He says that back in the '70s, "we had to build it, try it, build it, try it. Now our tools for developing this kind of stuff are just so much better."

[Source: AutoWeek]