New 2005 Jeep Grand Cherokee to Offer Cylinder Deactivation with HEMI

New developments such as high-speed electronic controls, sophisticated algorithms controlling the systems and the

MDS increases fuel economy by up to 20 percent while still delivering all the power and torque that the new HEMI V8 is becoming legendary for. (Photo: DaimlerChrysler Canada)

integration of electronic throttle control have made the technology possible. As a result Chrysler Group reports a seamless deactivation and activation process, needing only 40 milliseconds (0.040 seconds) to transition from eight-cylinders to four or vice versa.

So how does it work? Essentially MDS deactivates the valve lifters in four of the V8's cylinders (1, 7, 4 and 6), resulting in four closed valves and zero combustion in half the cylinders. Fortunately the "dead" cylinders don't drag energy from the

Chrysler Group conducted more than 10.5 million customer-equivalent kilometers of development and durability testing before the MDS-equipped HEMI became available. (Photo: Trevor Hofmann, Canadian Auto Press)

working four, due to air being pumped through those cylinders temporarily out of action.

"The MDS was part of the engine's original design," said Bob Lee, Vice President Powertrain Product Team, Chrysler Group. "This resulted in a cylinder-deactivation system that is elegantly simple and completely integrated into the engine design. The benefits are fewer parts, maximum reliability and lower cost."

In case the reliability of such new technologies concerns you, Chrysler Group conducted more than 10.5 million customer-equivalent kilometers (6.5 million miles) of development and durability testing before the MDS-equipped HEMI became available. The automaker adds the additional comfort of a 7-Year/120,000 km limited powertrain warranty as well.