The new Dodge Durango and Chrysler Aspen Hemi hybrids will share technology and basic transmission pieces with the hybrid GM SUVs, BMW X6, Mercedes-Benz M-Class, the next Ram, and potentially the Dakota. The main benefit is urban fuel economy with EPA at 19/20 mpg; over a mellow 145-mile ride ideal for economy and doing our best feather-footing, according to our on-board trip computer, we bettered those city and highway numbers.
With big utility hybrids like these, the term "no compromises" is tossed around with reckless abandon. Of course, there are compromises, primarily a lower tow rating (4700 pounds with the truck fully loaded) and an additional $3600 premium over a similarly equipped gas model. And some buyers may have a problem with no middle-row bucket seat option, no 2WD or low-range 4WD versions, a lux trim only, and less do-it-yourself serviceability. However, Chrysler claims the estimated tax credit of $1800 and a roughly $8000 advantage over the Tahoe hybrid.
The Hemi is a 345-horsepower, 380-pound-foot version of the 2009 V-8 with cam-in-cam variable timing but without the two-tract intake. It's mated to the two-mode transmission, which contains a pair of AC synchronous 65-kilowatt (87-horsepower/235 pound-feet) electric motors, but total system power output is kept to 385 and 380 (340 pound-feet available from 2000 rpm). A 152-pound NiMH 300-volt battery pack resides under the center-row seat, and it's all run by processing power (equivalent to three Mac G4s) that also tells the Hemi controller what it wants. The four fixed-ratio gears are used because they can't be beaten for power transmission efficiency in certain heavy-load situations.
Other changes include a separate cooling circuit, 25-watt pump and heat exchanger for the inverter/controller, an electric fan for the radiator stack, 4.5-kW motor to drive the air-conditioner's compressor, and a cabin humidity sensor below the rearview mirror to minimize compressor cycle time. The steering system from TRW is used on many European vehicles, employing a 1.5-kW motor to drive the pump feeding the standard hydraulic rack.
With added regen braking and no change to GVWR, the braking system wasn't upgraded--just adapted to electronic control. Fuel capacity remains 27 gallons in a reconfigured tank, the existing 18-inch tires were good for rolling resistance, and no spoilers or light body panels have been added.
Inside, a power gauge replaces the tachometer, "ready" and wrench/lightning bolt "high voltage service" lights have been added, and the nav screen offers system function/battery condition on a simple graphic to minimize distraction. When the Hemi's in MDS four-cylinder mode, the engine on the screen is color-split in half and the overhead mpg readout displays a fuel-saving mode.
Unless the battery is drawn down, the truck starts in electric mode. While you can get the hybrid up to 28 mph on electric power alone, the gas engine usually joins in at about 10 mph. Once it does, it often changes revs of its own accord, providing a bit of that CVT boat-reaching-planing-speed sensation. Mash it and the Hemi howl begins, and rolling to a stop yields an electric-motor/planetary gear whine supercharger fans will enjoy. If you focus on it, you can discern the transition between electric only and hybrid drive, but we suspect most owners won't notice, especially if they have the radio on and aren't watching any instruments or displays. Heavy braking, steering, and handling feel the same as a regular model with two passengers on board.