- The Washington Times - Friday, July 25, 2008

Most automakers believe there will always be a market segment for drivers who truly need a large vehicle. Big families who need space for lots of people and stuff simply can’t get by in something smaller.

Those who use their large SUVs for towing boats or recreational vehicles or hauling work loads won’t find much use for smaller vehicles either. They just want vehicles with full-size performance and capability that won’t break the bank at the gas station. For now, hybrid trucks seem to offer the most promise.

Chrysler’s first venture into hybrid vehicles involves its two full-size SUVs, the Chrysler Aspen and Dodge Durango. Both use a state-of-the-art gas-electric hybrid system, developed by a partnership with General Motors, Mercedes-Benz and BMW. This system integrates proven automatic-transmission technology with a hybrid-electric drive.

Because it offers low- and high-speed Electric Continuously Variable Transmission modes, the system is defined as a “two-mode hybrid.” In addition, the system incorporates four fixed-gear ratios for high efficiency and power-handling capabilities.

During the two ECVT modes, the system can use the electric motors for acceleration, improving fuel economy or for regenerative braking. The energy is stored in a battery pack for later use.

In the first mode, the two-mode hybrid provides all of the fuel-saving benefits of a full-hybrid system, including electric-only operation. In this mode, the engine is “shut off,” with the vehicle moving under electric-only power at low speed. The result is a significant reduction in fuel consumption in heavy stop-and-go traffic.

The second mode is used primarily at highway speeds. In addition to electric assist, the second mode provides full power from the 5.7-liter HEMI V-8 when conditions demand it, such as when passing, pulling a trailer or climbing a steep grade.

With its complex, yet elegant design, the two-mode system also packages two compact, powerful electric motors that fit inside a conventional automatic transmission case. It offers a clear packaging advantage compared with today’s typical single-mode systems that rely on much larger electric motors.

A controller determines when the vehicle should operate in the first or second mode. Input from the controller determines the necessary torque for the driving conditions and sends a corresponding command to the engine and electric motors. The engine and electric motors transfer torque to a series of gears in the transmission, which multiply torque similar to a conventional automatic transmission to move the vehicle.

Unlike conventional Continuously Variable Transmissions, the two-mode full hybrid’s electrically controlled system uses no mechanical belts or bands. Shifts between the two modes are synchronous, meaning no engine speed changes during a change of modes, for almost seamless acceleration.

The 300-volt battery pack provides electric power for the system, and is designed to fit in the vehicle without compromising passenger space.

A rectifier located under the vehicle’s hood converts AC to DC, to power conventional 12-volt accessories, such as interior lighting, climate control and the audio system. The vehicle’s internal-combustion engine efficiently maintains the battery pack.

Capable of towing 6,000 pounds, the 2009 Chrysler Aspen and Dodge Durango Hemi Hybrid vehicles can deliver a total output, of 385 horsepower and 380 pounds-feet of torque.

In hybrid form, the Hemi continues to feature Chrysler’s MDS technology, which allows the engine to seamlessly alternate between four-cylinder mode when less power is needed and V-8 mode for more power.

The assistance from the electric motors allows the Hemi to remain in four-cylinder mode longer than without a hybrid powertrain. Chrysler says preliminary fuel estimates are 18 miles per gallon city, 19 mpg highway. That is a considerable improvement over a 4-wheel drive Durango with a 5.7-liter Hemi, which gets 13/18 mpg. Chrysler anticipates customers will be able to reduce fuel consumption by several hundred gallons of gas annually.

The ML450 will be the first Mercedes application of the two-mode hybrid system. GM is building the two-mode transmissions for its vehicles, as well as supplying Chrysler. Similarly, Mercedes will build the transmissions for both its own and BMW’s vehicles.

The X6 will be the first BMW model to get the hybrid system. The internal workings are the same for all versions, but the software controlling all system functions will be tailored to suit individual manufacturers’ needs.

Pricing for the Chrysler Aspen Hybrid is $45,570 and the Durango, $45,430.

Chrysler boasts its new hybrids will sell for $8,000 less than the Chevrolet Tahoe and GMC Yukon Hybrids, which are on sale now, using the same hybrid system as the new Chrysler products. Shop around.

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