Detroit 2008: Saturn Vue 2-mode hybrid

Click the Two-Mode Vue for a high-res gallery

Saturn introduced the first General Motors production hybrid vehicle when the Saturn Vue Green Line appeared in 2006. The Vue was equipped with GM belt-alternator-starter (BAS) mild-hybrid system. The BAS system has subsequently been added to the Aura and Malibu sedans in addition to the redesigned 2008 Vue. The functionality of the BAS system is limited, providing start-stop functionality, some regenerative braking and some power boost from the motor. It cannot, however, run the vehicle solely on electricity.

For the 2008 Detroit Auto Show, Saturn is introducing what will be the second of three hybrid variants of the Vue. This one uses the Two-Mode hybrid technology that was introduced in 2007 on the Chevy Tahoe and GMC Yukon. Unlike the big GMT900 SUVs, the Vue has a transverse mounted engine and front wheel drive. That required designing a new transaxle that incorporates the same technology as the big trucks. Read on after the jump to learn more.

[Source: General Motors]

Because of the limited space in smaller vehicles, this transmission had to be repackaged to get all the hardware to fit. Like the rear wheel drive Two-Mode transmission, the new transverse mount version also features two electric motors. This version uses smaller 55kW motors compared to the 60kW units on the big trucks. The motors are still liquid cooled and they trade electrons back and forth with a 1.8kWh nickel metal hydride battery pack. The battery pack in the Vue is mounted under the cargo floor behind the rear seat. Unlike the air-cooled pack used in the Tahoe/Yukon, the Vue pack is liquid cooled.

Like the big truck hybrids, GM combined this Two-Mode system with the largest engine available in the non-hybrid version. That means the Two-Mode Vue uses the 3.6L "high-feature" V-6. The hybrid version is equipped with variable valve timing and direct fuel injection. The direct fuel injection allows the engine to use a higher compression ratio of 11.3:1 with less risk of pre-ignition. The engine also a knock control system specific to each cylinder that allows spark timing to be varied.

The functionality of the Two-Mode system itself is the same the rear wheel drive system. There are two hybrid modes for lower and higher speeds that use two variable ratio ranges. At higher speeds, the Two-Mode transmission also has a clutch that can lock in any of four fixed gear ratios. This mode mechanically bypasses the electric motors for greater efficiency at highway speeds.

To maximize the fuel efficiency and allow for more electric drive time, the Two-Mode Vue has an electro-hydraulic brake system that blends regenerative and friction braking. ( Disclaimer: I formerly worked for the company that produces the brake system for the Two-Mode Vue and I helped develop the brake control software). Since, unlike the mild hybrid, the Two-Mode is capable of running in electric drive mode, a brake boost system that doesn't rely on engine vacuum is needed. The electronic brake system used in the Vue (and the Tahoe) provides integrated hydraulic brake boost so that a vacuum pump isn't needed as it is on some other hybrids. This helps simplifies packaging and reduce noise.

Regenerative braking can come in at any speed, and any combination from 100 percent regen to 100 percent friction braking is possible. The percentage of regen depends on the amount of deceleration requested by the driver's brake application and the state of charge of the battery. Under most normal braking situations, the majority of which are less than 0.3g of decel almost all the braking will come from regen. Deceleration beyond about .35g, or when the battery is fully charged will add in friction braking. The regen limit is in part due to the rate at which the battery can absorb energy. In addition to regen blending, the brake system also provides full anti-lock braking, traction control and electronic stability control.

Other mechanical changes to the Two-Mode Vue include re-calibrated spring rates, anti-roll bars and damping rates to compensate for the changes in weight distribution the hybrid transmission and battery. The new hybrid also gets an electric power steering system. On the inside, the Two-Mode Vue varies from other models with an efficiency gauge replacing the tachometer. If the optional navigation system is included, a power flow display is available on the center stack display.

The bottom line is that the two-mode hybrid system allows the Vue to retain all the performance of the standard V-6 Vue including the 3,500lb towing capacity and 7.3 second 0-60 time. At the same time the fuel economy gets a 50 percent bump in urban driving and 30 percent overall. The Two-Mode Vue goes into production late in 2008.


GM's Advanced Hybrid Technology Delivers Up To 50-Percent Fuel Economy Increase
With No Compromises in Performance, Capability

  • First brand to offer two hybrid options on the same model
  • Third hybrid in Saturn's portfolio
  • Advanced Technology Partial Zero Emissions Vehicle (ATPZEV)

DETROIT – The all-new 2009 Saturn Vue Green Line 2 Mode, the first front-wheel-drive compact SUV in the world powered by General Motors' two-mode hybrid technology, is designed for customers who want the outstanding fuel savings of an advanced hybrid and the full power and towing capability of an SUV. The Vue Green Line 2 Mode was unveiled today at the North American International Auto Show.

The Vue Green Line 2 Mode will deliver an estimated 50-percent fuel economy increase over the non-hybrid V-6 Vue. It also is expected to have a driving range of more than 500 miles (800 km).

In addition, the Vue Green Line 2 Mode's 3.6L VVT V-6 engine with direct injection technology ensures there are no trade-offs between performance and fuel economy. Acceleration time from 0-60 is expected to be around 7.3 seconds, and the maximum towing load will be 3,500 pounds (1588 kg).

Production is slated to begin in late 2008.

"The Saturn Vue Green Line 2 Mode challenges the notion that a compact SUV can't be both powerful and efficient," said Jill Lajdziak, Saturn general manager. "Customers tell us they want a compact SUV that will respect the environment and save money at the gas pump, but they don't want to give up performance and utility. We've responded with the Vue Green Line 2 Mode."

The 2009 Saturn Vue Green Line 2 Mode sports the same European-inspired design language of the non-hybrid Vue, completely redesigned for the 2008 model year. Subtle exterior changes include "2 Mode" badging on the front doors and rear liftgate; and lightweight aluminum alloy wheels and low-rolling resistance tires that enhance fuel economy. The Vue Green Line 2 Mode's appearance is further accented by chrome door handles, chrome dual exhaust tips and chrome skid plates on the front and rear lower fascia.

The Vue Green Line 2 Mode features technologies and refinements in the fuel and exhaust systems that classify it as a Partial Zero Emissions Vehicle (PZEV) in the state of California and other states that have adopted California's motor vehicle emissions rules. When it arrives in dealer showrooms in the fourth quarter of 2008, the Vue Green Line 2 Mode will be Saturn's third hybrid, joining the Vue Green Line 4-cylinder hybrid SUV and the Aura Green Line sedan.

The Vue Green Line 2 Mode is GM's first application of two-mode technology on a front-wheel-drive vehicle. The system is currently on the V-8-equipped Chevrolet Tahoe 2 Mode and GMC Yukon 2 Mode full-size SUVs, and becomes available in 2008 on the Cadillac Escalade 2 Mode luxury SUV and Chevrolet Silverado 2 Mode full-size pickup.

How the Vue Green Line 2 Mode Hybrid works

GM's two-mode hybrid system in the Vue Green Line 2 Mode improves fuel economy by the following operations:

  • Engine off at idle
  • Low-speed, electric-only propulsion
  • Cutting off fuel to the engine during vehicle deceleration
  • Regenerative braking
  • Energy-efficient accessory systems

Unlike single-mode hybrid technology found in competitors' SUVs, the two-mode system maximizes city and highway fuel economy by integrating two electric continuously variable modes with four fixed mechanical gear ratios. The system consists of twin, active-cooled 55-kW electric motors integrated into the 2MT70 automatic transmission. Energy to power the motors comes from a 1.8 kWh, 300V nickel-metal hydride battery pack, which consists of 22 nickel metal hydride modules and is packaged behind the second-row seat below the cargo floor.

The transmission is mated to GM's 3.6L V-6 VVT with direct injection technology. In the first mode, at low speed and light load, the Vue Green Line 2 Mode operates in one of three ways depending on conditions and battery charge level: all-electric power, internal combustion engine power or a combination of the two. All reverse operation is driven by the electric motors.

The second mode is used primarily at highway speeds to optimize fuel economy. It provides electric assist in addition to six-cylinder power when conditions demand it, such as trailer towing and climbing steep grades, and to allow the engine to run at its most efficient point under less-demanding conditions.

No engine speed changes are necessary for the mode shift to occur. The result is exceptionally smooth, seamless acceleration and responsiveness. At all times, the system's Hybrid Optimizing System (HOS) collects torque-based data, deciphers it, then determines the most fuel-efficient means of propelling the Vue Green Line 2 Mode.

Direct injection V-6 boosts efficiency

The Vue Green Line 2 Mode's standard engine is an advanced 3.6L V-6 VVT with direct injection, a member of GM's family of high-feature V-6s. The direct injection engine uses regular unleaded fuel and represents one of the most sophisticated applications of its kind on a hybrid SUV.

Direct injection delivers fuel directly to the combustion chambers and permits a higher compression ratio, improving fuel efficiency. Additionally, the technology reduces cold-start hydrocarbon emissions by up to 25 percent.

The 3.6L VVT with direct injection also features a U.S. auto industry-first isolated fuel injector that greatly reduces the ticking noise associated with other direct injection engines. Other noise-reduction features include the use of acoustic foam in the engine valley and cover.

Specially tuned chassis for a smooth ride

Because the hybrid system changes the weight distribution on the Vue Green Line 2 Mode, special chassis refinements such as revised front and rear spring rates; revised front and rear stabilizer bar rates and recalibrated front struts and rear shock absorbers help ensure a smooth driving experience.

The Vue Green Line 2 Mode is equipped with a "fully blended" electro-hydraulic brake system that enables 100-percent regenerative braking (batteries are charged during braking), 100-percent friction braking (traditional four-wheel disc braking) or a combination of the two. During regenerative braking, the system converts kinetic energy to electrical power, then stores the power in the Energy Storage System.

A 12V rack-mounted Electric Power Steering system replaces a conventional column-mounted hydraulic system and saves fuel – gaining up to a half-mile per gallon of gas. It also gives the Vue Green Line 2 Mode more precise steering inputs and better overall on-center feel.

Intuitive displays keep drivers in the know

The Saturn Vue Green Line 2 Mode's instrument panel lets drivers know that they're behind the wheel of a sophisticated hybrid, yet with gauges that are easy to understand. An efficiency gauge replaces the tachometer, informing drivers of when they are achieving maximum fuel economy; whether the vehicle is in electric-only mode, engine-only mode or a combination of the two; and, because of the silent start as the key is turned, a telltale indicates when the vehicle is on and ready to drive.

In the center console, a full-color VGA power-flow graphic, which is integrated into an available navigation system, continuously informs the driver and passenger whether the vehicle is sending power to the wheels from the battery pack, engine or both. It also indicates when energy is being captured during braking.

Vue Green Line 2 Mode is generously equipped

In addition to its high-tech propulsion system, the Saturn Vue Green Line 2 Mode boasts a number of standard safety features including four-wheel anti-lock brakes, electronic stability control, rollover detection system, pedestrian impact protection, tire pressure monitoring system, Pedal Release System, front active head restraints, and six air bags (driver and front passenger frontal and seat-mounted side-impact, and roof rail curtains for both seating rows).

Other features include power-adjustable heated outside mirrors, leather-wrapped steering wheel with integrated audio and cruise controls; and a six-speaker AM/FM stereo with CD/MP3 player and auxiliary input jack. A navigation system and power sunroof are available.

Saturn's hybrid family is growing

The Vue Green Line 2 Mode is the third hybrid to join the Saturn lineup. Other members of the Green Line family include the Vue (4-cylinder) Green Line and the Aura Green Line sedan. They are equipped with the affordable GM Hybrid system, which reduces fuel consumption using sophisticated controls and a unique electric motor/generator mated to a 2.4L Ecotec VVT four-cylinder engine and Hydra-Matic four-speed transmission.

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