|Two-mode system for the 2008 Tahoe Hybrid. The first mode (1) is used for low speeds and light loads, while the second mode (2) is primarily used at highway speeds.|
General Motors will feature six new models, including two production hybrids and two new concepts at the North American International Auto Show in Detroit that begins on Sunday.
GM will feature the 2007 Saturn Vue Green Line mild Hybrid (earlier post), due to go on sale in mid-2006. The company will also preview the upcoming 2008 Chevrolet Tahoe Two-mode Hybrid featuring the first application of the two-mode full-hybrid system (earlier post) in an SUV.
The VUE mild hybrid uses GM’s Belt Alternator Starter (BAS) mild hybrid system which enables early fuel cutoff to the engine during deceleration and shuts off the engine at “idle”. Regenerative braking and optimized charging combined with an energy storage system further enhance fuel economy while maintaining all vehicle accessories and passenger comfort systems during the periods when the engine is temporarily shut off.
Early projections on the BAS systems indicate a range of improvement in fuel economy of around 10%–12%, which should take the VUE hybrid into the range of mid-to-upper 20s mpg US.
The two-mode system is under joint development by General Motors, DaimlerChrysler and BMW (the last two of which will likely make two-mode announcements at the Detroit show also).
The two-mode hybrid system is designed to optimize power and torque for different types of driving conditions.
The first mode provides fuel-saving capability in low-speed, stop-and-go driving with a combination of full electric propulsion and engine power. In the first mode, the vehicle can operate in three ways: electric power only, engine power only, or in any combination of engine and electric power.
The second mode is used primarily at highway speeds to optimize fuel economy, while providing full engine power when conditions demand it, such as trailer towing or climbing steep grades.
The 2008 Chevrolet Tahoe Two-mode Hybrid will feature two 60-kW motors in the hybrid drivetrain, a 300-volt battery pack and a Vortec V-8 engine with Active Fuel Management (displacement on demand), cam phasing, late-intake valve closure and very high compression ratio. GM is estimating an improvement in fuel economy of 25%, thereby taking the Tahoe into the low- to mid-20s mpg US range.