How far Jeep has come since these simpler times! Now, rather than buying powerplants from its rival, it leads the entry-level

The 5.7-litre HEMI not only produces the most horsepower and torque in the entry-level luxury class, but its MDS technology can reduce fuel consumption by up to twenty percent. (Photo: Trevor Hofmann, Canadian Auto Press)

luxury SUV segment in engine output and technology. That's right. The 5.7-litre HEMI not only produces the most horsepower and torque in the entry-level luxury class, at 330-hp and 375 lb-ft respectively, but the engine's standard Multi-Displacement System (MDS) technology, that can reduce fuel consumption by up to twenty percent under light loads, not only beat all rival systems to market when it debuted on the Chrysler 300C, but also became the first cylinder deactivation system available in a 4x4 capable SUV when the recently revised Grand Cherokee debuted last year.

Recent

The Commander's MDS cylinder-deactivation system works seamlessly. (Photo: Trevor Hofmann, Canadian Auto Press)

developments, such as high-speed electronic controls, sophisticated algorithms controlling the systems and the integration of electronic throttle control, have made reliable integration of the cylinder-deactivation 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 theV8'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 working four, due to air being pumped through those cylinders temporarily out of action.