2009 Dodge Durango HEMI Hybrid Preview

2007 Dodge Durango

New hybrid posts 40-percent fuel gain. by Bengt Halvorson (2007-11-13)

Chrysler has pulled the wraps off its upcoming Dodge Durango HEMI Hybrid and Chrysler Aspen HEMI Hybrid models.

In the Durango and Aspen hybrids, the new hybrid powertrain incorporates Chrysler's 5.7-liter HEMI V-8, also featuring the automaker's Multi-Displacement System, which shuts down half of the engine's cylinders during low-load conditions such as coasting or low-speed cruising. Together, the V-8 and electrical motor system produce 385 horsepower.

The so-called two-mode hybrid system employed in the Durango and Aspen, developed in conjunction with General Motors, BMW, and Mercedes-Benz at the jointly operated Hybrid Development Center in Troy, Michigan - and similar to the one being used in the Chevrolet Tahoe and GMC Yukon hybrids - is a 'full-hybrid' one, meaning that in addition to turning the V-8 off completely at stoplights, it can use the electric-motor system to propel the vehicle alone without the gasoline engine for short, low-speed distances.

All the components of the system, including electric motors, the transmission, the battery system, energy management devices, and system control units were developed at the center, and the electric motor system and transmission were designed to fit in the packaging space of a conventional automatic transmission. The modular design employs electric motors that transfer torque directly to a series of gears in the four-speed automatic transmission, as commanded by a control unit, for seamless mode transfers between electric and gas power.

The 300-volt battery pack, which is charged during braking and deceleration and maintained in a particular range of charge by a sophisticated management system, is packaged so as to not compromise passenger space. Under the hood there is a rectifier to convert the AC current to DC for standard 12-volt vehicle accessories.

At 5553 pounds, the Aspen HEMI Hybrid tips the scales at about 500 pounds more than the Chrysler Aspen Limited 4WD. Towing capacity for the non-hybrid model maxes out at 8950 pounds, but the Hybrid model is still approved for trailer towing and good for a still-impressive 6000 pounds. Both models have four-wheel drive, through a single-speed transfer case. The system normally sends 52 percent of torque to the rear wheels.

Despite the greater weight, the efficiency gains for the Hybrid model look impressive, with the fuel economy estimate for the 4WD Hybrid models at a tentative 18 city, 19 highway. Just looking at the posted numbers, that places the Hybrid's improvements at nearly 40 percent in the city and about five percent on the highway versus the HEMI model. Currently the Aspen and Durango 4WD are rated 13/18 when equipped with the HEMI V-8, which already includes the MDS system, and the V-6 model, with rear-wheel drive and a four-speed automatic, gets 14 city, 19 highway.

"Combined with Chrysler's Multi-displacement System (MDS), our advanced two-mode hybrid technology immediately delivers a more than 25-percent fuel economy improvement to our full-size SUVs - and up to a 40-percent improvement in the city," said Frank Klegon, Chrysler's product development chief, in a company release that accompanied the announcement.

Chrysler had previously been criticized for cutting a previous Durango hybrid model, under development earlier this decade and originally due in 2003. That vehicle had a mild hybrid system and lower estimated fuel efficiency than the new HEMI Hybrid, despite using a V-6 engine.

The new Hybrid models will begin arriving at showrooms next summer.