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The Two-Mode Hybrid System is the result of an agreement between automakers GM, Chrysler and BMW to cooperate on the development of hybrid motor technology. More than 500 engineers and technicians from the three firms were charged with the development of the new two-mode hybrid system
technology.
This cross-manufacturer cooperation has resulted in a full two-mode full hybrid propulsion architecture that is claimed to be much more efficient than the hybrid
motors currently available.
Until now, US hybrids have used a single-mode hybrid motor. In general, the single-mode system uses larger motor sizes than are necessary for the two-mode system.
Vehicles emloying the Two-Mode Hybrid system use significantly smaller engines that are physically about the size of an automatic transmission.
In fact, the two-mode hybrid system merges the vehicle's automatic transmission with the hybrid technology motor, resulting in increased efficiency while producing approximately the same horsepower (and even more in some cases)as today's single-mode hybrid motors.
Blended Options
The two-mode system will allow vehicles to operate differently at different speeds. The system can operate on "battery only" at lower speeds. But at faster speeds, the system can use a "gas only" mode or a "blended" mode, depending on the horsepower and acceleration required. This diversity is the real selling point of the two-mode hybrid systems, and it allows them to function effectively in
a wide variety of vehicle types.
Additionally the two-mode hybrid system can be applied to front, rear or all-wheel drive vehicles with equal success. And while the current configuration is ideal for larger, heavier vehicles (like full-size trucks), it can easily be converted for use in smaller, more fuel-efficient vehicles.
The Two Mode System in Use
In practical use, the first mode is active during in-town, stop-and-go driving, and up to speeds of around 40mph. The second mode activates to assist in fuel efficiency during faster speeds and in highway traffic. While the current crop of hybrids has been efficient at conserving fuel during in-town driving, they have been of virtually no benefit when approaching highway speeds (40mph and
above).
GM and Dodge trucks are the first US vehicles to take advantage of the two-mode system, beginning with a several full-size 2007 model trucks. GM is estimating that the two-mode system offers an improved fuel economy of approximately 25 percent in both city and highway use from current models while sacrificing little or no horsepower.
Power To Spare
According to GM, the Two-Mode Hybrid System also increases towing and pulling power, making it ideal to be included with a full-size truck. The idea is to conserve more energy when the truck is not being "pushed hard," but have extra
horsepower available when it is needed, resulting in a net "savings" of fuel and increased efficiency.
GM is also using the new two-mode system with several other vehicles. The Chevy Tahoe for one example. Meanwhile, Chrysler will offer the 2008 Dodge Durango with a full two-mode hybrid system.
Over the next few years, the two-mode hybrid system is set to become the standard, gradually replacing the single-mode hybrids on the road today. At least until a more efficient design comes along.