GM showcased its front-wheel-drive, two-mode hybrid technology in its 2008 Saturn Vue Green Line. The SUV contains two electric motors, a gas engine, and four fixed-ratio planet gears. One motor usually acts as a generator to keep the nickel-metalhydride battery pack charged. But under load, the motor helps propel the vehicle. The output from the other motor, on the other hand, always goes to propelling the vehicle. The term “two-mode” came about because the vehicle operates in two ways: The first mode works at low speeds and low loads. Here, the car moves with either the motor, the internalcombustion engine (ICE), or a combination of the two. If the vehicle is under electric power alone, such as at idle, the controller will restart the ICE when it needs more power.
Saturn Vue Green Line Hybrid | Characteristics | Ford Escape Hybrid |
Ecotec 2.4 L4 | Engine | 2.5 L Atkinson |
25 / 32 | EPA fuel, mpgg | 31 / 34 |
180.1 | Length, in. | 174.7 |
72.8 | Width, in. | 71.1 |
66.2 | Height, in. | 67.7 |
56.4 | Cargo volume, ft3 (behind front row) | 61.1 |
1,500 | Towing capacity, lb | 1,000 |
$24,170 | MSRP, $ | $29,305 |
The second mode operates at higher loads and speeds. Here, the ICE is always running. Variable intake and exhaustvalve timing supplies full power under high loads as well as good fuel economy while cruising. The ICE also uses valve timing to increase efficiency.
As the vehicle speeds up, various planet gears engage or disengage. This boosts or lowers engine torque and lets one of the electric motors supply power or switch back to generator mode. This continues while the SUV’s speed or load changes under different road and traffic conditions. The SUV also uses regenerative braking. Basically, hitting the brake recharges the batteries. EPA fuel estimates the SUV gets 25/32 mpg. So we were a bit disappointed when our tester averaged about 24 mpg on city streets and country highways.
Driving-wise, our tester proved more like a car than an SUV. Its 169 hp at 6,200 rpm provided plenty of go-power. Fortunately, the four-wheel antilock disc brakes stopped on the proverbial dime.
A standard vehicle costs about $24,000. Adding the comfort and convenience package (with power-adjustable driver’s seat, leather-wrapped steering wheel, and lighted visor mirrors) brings this to $25,720.00.
— Leslie Gordon