Which Hemi Engines Have MDS?by Steve Johnson
The term "Hemi" engine was trademarked by the Chrysler Corporation in 1964; however, the concept and same technology is used by other companies under different names. The Multi-Displacement System (MDS) is also a Chrysler-developed technology involving variable engine displacement. It is similar to the Active Cylinder Control, Active Fuel Management and Variable Cylinder Management technologies developed by Mercedes-Benz, GM and Honda, respectively.
The Chrysler Hemi Engine
The Hemi engine was an internal combustion engine designed by Chrysler that utilized a hemispherical combustion chamber. This allowed the valves to be in-line rather than side-by-side, which resulted in a simpler airflow and larger valves. This powerful engine found use in the XP-47 aircraft where it generated a maximum power of 2,500 to 3,500 horsepower. It was also used in experimental tanks. It became popular when it won the first three places in the 1964 Daytona 500 auto race. The modern Hemi differed greatly from the original Hemi, with only the perpendicular valve arrangement remaining. They replaced the Chrysler LA engine line in the early 2000's. The modern Hemi was released with 5.7L, 6.1L, and 6.4L displacements, all of which featured MDS. The latest 6.4L version had a maximum power of 525 horsepower.
The MDS technology allowed the deactivation of some cylinders when they are not needed. At low power, the MDS only activated four cylinders. When more power was needed, the V-8 mode was activated. According to Chrysler, this resulted into fuel economy with up to 20 percent more efficiency. This system also resulted in fewer parts for the engine, thus lowering costs. The MDS was enabled through the Electronic Throttle Control system. This allowed seamless transition from eight to four cylinders in about 0.040 seconds.
MDS-Equipped Hemi Engines
The 5.7L Hemi V-8 engine with MDS was available in a number of Dodge, Chrysler and Jeep vehicles. In 2005, it was available in the Chrysler 300C, Dodge Charger, Dodge Magnum and Jeep Grand Cherokee. In 2006, it was equipped in the Dodge Durango, Dodge Ram 1500 and Jeep Commander. It then became available for the Chrysler Aspen in 2007 and Dodge Challenger in 2009. As of December 2010, the Car and Driver website says the 6.4L Hemi V-8 engine with MDS will be available in the 2011 Dodge Challenger SRT8, as well as the other upcoming SRT V-8 models. However, the MDS will not be available in cars with manual transmissions.