The 2007 Saturn Vue Green Line Hybrid features a unique electric motor/generator mated to a 2.4L VVT four-cylinder engine and 4T45-E four-speed transmission powertrain to deliver increased fuel economy over non-hybrid models. It is a less complex, lower-cost hybrid system than competitors' systems. The Vue's hybrid system enables increased fuel economy through engine shut-off at idle, fuel cut-off during deceleration, electric motor/generator assist during acceleration and the capability to capture electrical energy through regenerative braking. The Vue Green Line is expected to deliver an EPA estimated 27 mpg in the city and 32 mpg on the highway.

Six elements comprise the hybrid system:

• A precision electric motor/generator unit that replaces the conventional starter and alternator, and is capable of 115 lb.-ft. (156 Nm) of auto-start torque
• Engine-coolant cooled power electronics that control the motor/generator unit and provide 12-volt vehicle accessory power
• An advanced NiMH hybrid battery pack capable of delivering and receiving more than 10 kW of peak power – the battery pack is located beneath the cargo floor between the rear wheels, maintaining full vehicle utility
• An engine control module that includes sophisticated Hybrid Supervisory software to manage both the hybrid system and the gasoline engine
• An engine accessory drive with new, dual-tensioner assembly and durable aramid cord belt that enables transfer of "motoring" and "generating" torque (see below)
• Hybrid-enabled Hydra-Matic 4T45-E electronically controlled four-speed automatic transaxle that includes an auxiliary oil pump and unique hybrid controls.

The driving situation determines whether the vehicle operates in either motoring or generating mode. In motoring mode, the hybrid system is used to quickly restart the gasoline engine upon brake pedal release and provide momentary acceleration assistance as needed. To perform these functions, the NiMH battery pack converts its stored chemical energy into direct current (DC) electrical energy. The system's electronics then convert the DC power to three-phase alternating current (AC) energy to run the motor/generator unit as an electric motor. The vehicle's 12-volt accessory power also is generated in this mode.

In the generating mode, the hybrid system is used to provide both 12-volt accessory power and power to charge the battery pack. To perform these functions, the engine is used to power the motor/generator unit, which then provides a three-phase electrical output. In this mode, the energy required to drive the engine may come from either gasoline when accelerating, or the kinetic energy of the moving vehicle when decelerating with the fuel cut off. The three-phase AC electrical output of the motor/generator is then converted to DC energy to efficiently charge the hybrid battery pack and vehicle accessory battery.

A Green Line-specific instrument cluster with a new "charge/assist" readout indicates when the vehicle is in the battery charging or electrical assist modes, and a tachometer that has 'AUTO STOP' and 'OFF' readouts. AUTO STOP indicates when the engine shuts off and OFF indicates when the key is either turned off or removed from the ignition. Also, an 'ECO' indicator illuminates whenever instant fuel economy exceeds the EPA-average fuel economy ratings.

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Source: Saturn