By: Jeffrey Ross
Autotropolis.com
In the muscle-car era, no other powerplant had as much impact as the iconic Hemi engine. The raw, unadulterated Hemi offered Dodge and Plymouth drivers hours of tire-shredding fun. Unfortunately, the legendary Hemi engine met its ultimate match in 1971: fuel economy.
When the Hemi-branded engines were revived in 2003, well-known Dodge commercials had everyone asking Dodge Ram drivers, “That thing gotta Hemi?” This fall, full-size SUV buyers will be able to counter the Hemi commercials with their own tagline: “That thing gotta hybrid? Sweet!”
A joint development between DaimlerChrysler, General Motors and BMW will bring Dodge and Chrysler their first hybrid vehicles; a two-mode hybrid version of the Dodge Durango and Chrysler Aspen. The hybrid system will be paired up with the 335-horsepower, 5.7-liter Hemi engine featuring Multi-displacement System (MDS). DaimlerChrysler claims the pairing will improve overall fuel economy by 25 percent and a 40-percent gain during city driving alone.
The most unique aspect of this joint venture hybrid system is the transmission. While most of the hybrids on the market use a normal engine (gasoline or diesel) with two electric motors, the system that will find its way into the Durango incorporates the two electric motors into the transmission. This setup allows for high efficiency without sacrificing any power-handling capabilities such as acceleration or towing.
The two-mode hybrid transmission uses the two electric motors that act as an electric continuously variable transmission (ECVT) and four conventional fixed gears. This combination ensures that the Durango and Aspen will fit a wide variety of applications. When the 2006 Dodge Durango was redesigned and the 2006 Chrysler Aspen was released, both featured a floor design that would seamlessly accept the new hybrid system. This allows both SUVs to offer the efficiency of a gas-electric hybrid but maintain the passenger and storage capacities of a conventional full-size SUV.
The MDS Hemi operates as a regular V8 during acceleration or under a load and seamlessly switches to operate as a four cylinder engine while cruising, coming to a stop or idling. For comparison, the 2007 Dodge Durango and Chrysler Aspen get fuel economy of 14 mpg city and 20 mpg highway, while the 2008 hybrid version of the pair will get 20 mpg city and 22 mpg highway according to DaimlerChrylser claim. The MDS system alone improved fuel economy in the in the Hemi by 10 percent.
The first vehicle brought to market using this joint technology will be the 2008 Chevrolet Tahoe and GMC Yukon this summer. By 2009, General Motors will offer the hybrid technology in its entire lineup of full-size pickups and SUVs sharing the GMT900 platform, ranging from the Chevrolet Silverado to the Cadillac Escalade. GM’s hybrid SUVs will be powered the 320-horsepower, 5.3-liter V8 with the MDS-like Active Fuel Management.