VUE LEADS SUV MARKET WITH WIDEST CHOICE OF CUSTOMER-PLEASING POWERTRAINS

The Saturn VUE offers more powertrain choices than any other SUV, including 4- and 6-cylinder engines, front- and all-wheel drive, and three different transmissions.

"VUE's powertrains are a significant competitive advantage," said Jim Ulrich, Saturn vice president of engineering. "Both engines incorporate modern features such as lightweight construction, overhead cams and multi-valve combustion chambers to provide smooth, responsive and fuel efficient performance. The VUE also will be the first SUV to offer the innovative VTi variable transmission, and the first compact SUV with a five-speed automatic transmission."

2.2-liter 4-cylinder engine
The base engine on the Saturn VUE is the advanced Ecotec DOHC 16-valve, 2.2-liter 4-cylinder engine. With twin overhead camshafts and four valves per cylinder, it provides excellent response in urban driving and confident passing and merging on the highway.

This engine is a variant of the GM global 4-cylinder powerplant used in the Saturn L-Series. The version going into VUE has a slightly higher compression ratio (10.0:1 compared to 9.5:1), a result of flat-top pistons instead of the slight dish in the piston dome in the L-Series version. The net result is slightly more horsepower and torque in the VUE, which registers 143 hp at 5600 rpm, and 152 lb-ft of torque at 4000 rpm.

A key performance attribute of the engine is near-maximum torque over a broad rpm range. More than 90 percent of peak torque is available from 1500 to 5700 rpm.

On the VUE, the 4-cylinder engine is mated with either the standard five-speed manual transmission or VTi variable transmission, and is available with either front-wheel drive or all-wheel drive.

The 2.2-liter engine features twin balance shifts for quiet operation. These shafts, located in the cylinder block, counteract the vertical shaking forces inherent in an inline 4-cylinder engine, resulting in an engine that is smooth from idle to maximum engine speed. A die-cast lower crankcase and cast-aluminum oil pan provide extra structural rigidity and reduce radiated engine noise. An isolated aluminum cam cover reduces the transmission of valvetrain noise.

A lost-foam casting process is used for the aluminum block and heads. The process uses a highly accurate foam pattern to create the casting molds, allowing intricate designs to be cast into the block and heads, reducing cost and increasing reliability. For example, oil galleries, coolant passages and secondary air passages are part of the cylinder head casting, eliminating machining costs as well as add-on lines that can be a source of leaks.

And the housing for the cartridge-type oil filter is cast into the block, eliminating a mating surface that is a common source of leaks.

Cast-iron cylinder liners enhance durability, and their thin-wall design allows minimum bore spacing, contributing to a compact overall engine.

The engine's accessory drive system is designed for low mass, reduced noise and vibration, and ease of service. The water pump is driven by the balance shaft chain, instead of a belt.

The crankshaft is a nodular-iron casting with eight aerodynamically-shaped counterweights for excellent balance. Connecting rods are forged steel, and the cast aluminum pistons feature a 3 mm top piston ring land that reduces the amount of unburned fuel that can be trapped between the piston and cylinder wall.

The intake manifold, welded with composite material for light weight and reduced cost, is a scroll configuration that provides excellent breathing in a compact design. The catalytic converter is mounted on the exhaust manifold take-down pipe, rather than further down the exhaust system. This proximity to the exhaust manifold allows the catalytic converter to heat more quickly and achieve light-off - the temperature at which exhaust emissions are most efficiently oxidized - more quickly following a cold start.

The engine uses a tuned air induction system, tuned intake manifold and sequential port fuel injection with a returnless fuel system to reduce evaporative emissions. Other variants of the 2.2-liter engine have return lines from the fuel injectors that manage fuel pressure by bleeding off excess fuel and returning it to the tank. The engine used in the VUE replaces the return lines with an electric pressure regulator to manage fuel pressure.

Even without the addition of an exhaust gas recirculation (EGR) valve, the VUE 2.2-liter engine meets National Low Emission Vehicle (NLEV) requirements. It also meets Low Emission Vehicle (LEV) standards in California and Northeastern states when equipped with the 5-speed manual transmission, and Ultra Low Emission Vehicle (ULEV) standards in California and Northeastern states when equipped with VTi.

The Ecotec 2.2-liter engine utilizes a roller-type finger follower valvetrain for reduced friction and improved fuel economy and performance. Hydraulic lash adjusters eliminate the need for periodic valvetrain maintenance.

Other features that make maintenance easier include platinum-tipped spark plugs, long-life DEXRON III transmission fluid and DEX-COOL engine coolant, and an oil life monitoring system that calculates oil life based on engine operation to eliminate unnecessary oil changes while extending engine life.

3.0-liter V6 engine
Originally designed for sustained high-speed driving on German autobahns, the 3.0-liter V6 offered as an option on the VUE has earned an international reputation for smoothness, durability, reliability and excellent performance.

The 3.0-liter, dual overhead camshaft 24-valve V6 produces 181 horsepower at 6000 rpm, and 195 lb-ft of torque at 4000 rpm. In the VUE, the V6 is mated with a five-speed automatic transmission in an all-wheel drive configuration.

The cast-iron cylinder block features a 54-degree angle between banks, which allows a more compact design that also minimizes weight. The crankshaft and connecting rods are also cast iron. The rod and cap are machined as a unit. The rod cap is then separated by fracturing, assuring perfect alignment even under high operating loads for improved durability of the rod bearings.

A short-skirt piston design saves weight and improves engine smoothness. The 10:1 compression ratio yields excellent power and torque with high fuel efficiency.

The dual-overhead-camshaft cylinder heads are cast aluminum for low weight. The narrow 36-degree angle between the valves helps maintain the compactness of both the combustion chamber and the overall engine envelope. Spark plugs are located in the center of the combustion chambers for fast, efficient burning of fuel, enhancing performance while lowering exhaust emissions.

An advanced Bosch Motronic engine control system regulates fuel delivery, ignition timing, idle speed, the evaporative emissions system, and spark-knock control. By performing thousands of calculations per second, the Motronic computer can adjust key operating parameters three times per crankshaft revolution. Dual sensors (one per bank) facilitate cylinder-by-cylinder knock control. High-energy coil packs, mounted atop each cylinder-head cover, fire long-life dual-platinum-tipped spark plugs.

Advancements engineered specifically for the VUE application include a returnless fuel-delivery system to reduce evaporative emissions and a cast-magnesium intake manifold. The new bi-modal manifold provides long-length runners to boost low- and mid-range torque and shorter runners for maximum output at high rpm. Two valves (one per cylinder bank) controlled by the Motronic computer make the switch from long to short runners at the appropriate rpm. The use of magnesium instead of cast aluminum saves 10 pounds (4.5 kg) over the intake manifold used in previous applications.

The 3.0-liter V6 is certified to meet LEV standards in California and Northeast states and NLEV standards elsewhere in the U.S.

An oil-life algorithm programmed into the powertrain control computer automatically monitors operating conditions and advises the driver when an oil change is necessary. A paper oil filter cartridge is more readily disposable than metal-housed oil filters. DEXRON III transaxle lubricant is filled for life and DEX-COOL engine coolant lasts, 150,000 miles in normal driving conditions.

Development
Saturn customers expect high standards in the areas of quality, reliability and durability. To meet and exceed these expectations, Saturn engines must survive a grueling battery of endurance tests including:

• Over 2.5 million durability miles (4 million km)
• Over 8,000 hours of engine-dynamometer testing
• Over 150 different types of vehicle and system tests to ensure the powertrain is pleasurable, reliable, and durable
• Approximately 500 component-level tests with similar goals.
• 160,000 average customer-equivalent miles (260,000 km) logged in five weeks on selected vehicles
• 12,000 miles (20,000 km) of trailer towing performed on mountain roads in Arizona and Colorado
• Hot-weather tests up to 120 degrees Fahrenheit (48°c) performed at GM's Desert Proving Grounds in Arizona
• Cold-weather tests down to -40 degrees Fahrenheit (-40°c) performed at winter proving grounds in Kapuskasing, Ontario, Canada ·
• Extensive driving over gravel-, mud-, salt-, and snow-covered roads

The new VUE also has been put through "worst-case" scenarios - situations not likely to be encountered by the average customer. Additional worst-case scenarios include:

• Up to 10,000 miles (16,000 km) of wide-open-throttle operation including 3,000 miles uphill
• Up to 6,600 manual downshifts (automatic transmission)
• Up to 2,000 park engagements on steep hills (automatic transmission)
• Up to 1,500 miles (2,400 km) of driving on Belgian blocks and pot holes

Segments of the above tests are conducted with a full vehicle load including the weight of five passengers and their cargo.

VTi variable transmission
A significant innovation debuting on the Saturn VUE is VTi, a continuously variable transmission (CVT) developed by GM Powertrain.

VTi represents a new generation of automatic transmissions prompted by the desire to achieve greater fuel efficiency. While other makers have previously sold CVTs in the U.S. in modest volumes, VTi is slated for high-volume production and extensive use in various world markets.

VTi provides an infinite number of gear ratios with shifts that are a smooth, seamless progression, in contrast to the discrete ratio steps found in conventional step-gear designs, both automatics and manuals. Pressing the throttle delivers power for acceleration without any down-shift jolt. Other advantages are a significantly greater range between the lowest and high-available ratios, and the ability to coordinate the transmission's operation with the engine through electronic controls to deliver superior performance and response characteristics.

Saturn VUE engineers approached its engine-and-transmission combinations as integrated systems in order to maximize performance. As a result, VTi in the VUE will yield fuel economy comparable to a manual transmission, and about 7 percent better than a four-speed automatic. Estimated fuel economy for the VUE equipped with VTi and front-wheel drive is 21 mpg city, 28 mpg highway and 24 mpg combined. Models with VTi and all-wheel drive get an estimated 21 mpg city, 26 mpg highway and 23 mpg combined. In comparison, VUEs with the five-speed manual gearbox get an estimated 23 mpg city, 28 mpg highway and 24 mpg combined.

VTi also has 45 percent fewer parts than a four-speed automatic, reflecting its simpler overall design. While the concept of a CVT is not new, it took key advancements in metal drive belt technology and control system sophistication to make this transmission suitable for high-volume production.

Two variable-diameter pulleys are the key components. One side of each pulley is fixed in position, while the other is moved axially by an internal hydraulic piston. The metal belt connecting the two pulleys is squeezed between the four pulley drive surfaces to prevent slippage. A hydraulic pump supplies 700 psi of pressure to operate the pistons and to maintain tight belt-to-pulley contact.

Low gear occurs when the belt rides at the innermost radius of the driving pulley and at the outermost surfaces of the driven pulley. High gear occurs when the belt rides at the top of the driving pulley and at the bottom of the driven pulley. As long as there is equal pressure on both internal hydraulic pistons, the drive ratio remains constant. A pressure differential causes the belt to move lower in one pulley and higher in the other, changing the drive ratio.

VTi enables a greater overall ratio range than is possible with step-gear designs. Four-speed automatics have a 3.3-4.3 ratio range. A five-speed automatic may exceed a ratio range of 5.0. The VTi reaches a 5.92 ratio range. This larger ratio range optimizes acceleration, fuel efficiency and cruising comfort.

VTi's three-axis layout has three major components in line with the engine crankshaft: a fairly conventional electronically-controlled torque converter, a forward-reverse clutch and planetary gear set, and the input pulley. The output pulley lies on the second axis. The final-drive differential - which is linked to the output pulley via a pair of transfer gears - constitutes the third major axis. A chain-driven hydraulic pump is offset to the side for more compact packaging.

VTi's metal belt consists of more than 200 bow-tie-shaped alloy-steel elements held together by 10 spring-steel retention bands. Sides of the steel elements are cut to form a 22-degree angle matching the V-shape of the two pulleys. The belt operates in compression to transmit power from the input to the output pulley.

Through conducting a number of clinics, VUE engineers determined that Saturn customers want their vehicles to feel nimble and responsive. In line with those findings, the engineers tuned VUE's electronically-controlled throttle and torque converter clutch to yield excellent acceleration and quick throttle response with little apparent transmission activity.

The integration of all powertrain components allows the engine to spend more time in its most efficient operating mode, translating directly into low emissions and fuel consumption.

VTi's benefits are especially noticeable in mountainous driving, where automatic transmissions are constantly searching for the right gear. The VTi always maintains the most effective drive ratio, whether climbing, coasting down a grade or accelerating out of a tight switchback. With a trailer attached, the benefit is even more dramatic.

5-speed manual transmission
The Getrag manual transmission is fitted to VUEs equipped with the 2.2-liter 4-cylinder engine and front-wheel drive.

The lower ratios are properly spaced for excellent on- and off-road performance. Fourth and fifth gears are overdrive ratios for quiet, efficient cruising at highway speeds. A synchronized reverse gear eliminates clash and reduces engagement effort prior to backing.

The transmission design features a two-piece, die-cast-aluminum case, double-cone synchronizers for first and second gears, and heavy-duty carbon-fiber synchros for third, fourth, fifth and reverse gears.

5-speed automatic transmission
The Saturn VUE is one of the first General Motors vehicles in the world to offer a five-speed automatic transmission. The 5-speed is standard in VUEs equipped with the 3.0-liter V6 engine.

With a five-speed, the steps between ratios are closer, providing smoother acceleration particularly during passing. The broad range of overall ratios provides excellent low-speed performance plus outstanding fuel efficiency with low engine noise at highway speeds.

Electronic controls include an adaptive learning capability, so shift quality will not deteriorate as components wear throughout their service life. In addition, various shift schedules are available, depending on whether the VUE is climbing a grade, towing a boat or operating off-road. Load, rpm and throttle inputs provide the transaxle control computer with the information needed to select the appropriate shift schedule.

This automatic transaxle has an ultra-short axial length of 14 inches (356 mm), which enables it to fit in the same space as the other two transaxles engineered for the VUE.

All-wheel-drive system
The Saturn VUE offers an innovative on-demand all-wheel-drive system as an option with the 2.2-liter 4-cylinder engine, and standard with the 3.0-liter V6.

During normal driving on dry road surfaces, this driveline delivers power to the front wheels. If the front wheels slip due to adverse traction - caused by rain, snow, or a muddy driveway - power is automatically delivered to the rear wheels. The system works automatically and seamlessly with no action needed from the driver.

While it is engineered primarily for on-road use, the VUE all-wheel-drive system also provides excellent traction and mobility off-road. Unlike heavy-duty four-wheel-drive systems, this is a single-range design not intended for strenuous use.

The system's three major components are a power takeoff unit (PTU) attached to the transaxle, two-piece propeller shaft running longitudinally under the SUV floor, and compact rear drive module supported by a subframe that also carries the rear-suspension system.

The PTU is a compact aluminum housing that supports a ring gear and a pinion shaft. The ring gear is driven by the front differential carrier in the vehicle transaxle by a splined connection. It, in turn, turns the pinion shaft. The ring and pinion gear set changes the drive orientation from transverse to longitudinal and lowers the drive axis by one inch for optimum propeller-shaft packaging. Wheel speed is also stepped up by a 2.53:1 ratio to diminish the torque delivered by the propeller shaft, facilitating light and compact driveline components. The PTU contains its own sealed supply of hypoid gear lubricant.

The propeller shaft is a two-piece steel-tube design with a center support bearing attached to the vehicle floor. It attaches to the PTU through a plunging-cross-groove constant-velocity universal joint. The propeller shaft is permanently engaged so it rotates whenever the vehicle is in motion. However, torque is delivered to the rear wheels only when traction conditions warrant. If the front wheels slip, as much as 69 percent of torque is delivered to the rear wheels on 4-cylinder models, and up to 57 percent on V6 models.

The propeller shaft aft end is connected to the rear drive module. This device consists of a number of aluminum castings that contain two basic elements. At the front, there is a progressive coupling assembly. Directly behind that device is a second ring-and-pinion gear set and a conventional differential mechanism that delivers drive torque to both rear wheels through a pair of half shafts. A 2.53:1 ring-and-pinion ratio keeps rear wheel speed in synch with the VUE's front wheels.

The progressive coupling assembly (PCA) performs two key functions: it delivers drive torque from the propeller shaft to the rear differential and it automatically limits maximum torque to protect driveline components from overloading or abuse.

Inside the PCA are two key components - a gerotor pump and a multi-plate clutch pack. The outer portion of the gerotor pump is driven by the propeller shaft while the inner portion is mechanically linked to the rear axle. As long as there is no speed differential between front and rear axles, this pump simply rotates. But when front axle rotation exceeds rear axle rotation due to slippage at front of the vehicle, the resulting speed differential causes the gerotor device to begin pumping the filtered gear lubricant that circulates throughout the RDM.

The hydraulic pressure created by the gerotor pump is applied through a piston to the clutch pack. Inside, there are 10 steel reaction plates driven by the splines of the PCA outer housing. Nine friction plates interspersed between the reaction plates are, in turn, splined to a center hub mechanically connected to the rear differential's input pinion. When the gerotor pump creates hydraulic pressure, the reaction plates are forced into contact with the friction plates. As this occurs, torque from the propeller shaft is smoothly and progressively transmitted through the PCA to the rear differential.

Unlike many on-demand all-wheel-drive systems, the VUE's system is engineered to sustain a measured amount of slippage. Some of the lubricant pumped by the gerotor device is circulated through the clutch pack to provide a cooling effect that allows the clutches to operate in a slip mode without damage.

The hydraulic circuit that routes lubricant from the gerotor pump to the clutch-pack-apply piston contains two pressure relief valves that automatically limit the maximum torque that can be delivered by the PCA. Two valves are needed for sufficient flow capacity and to provide a fail-safe mode in the event one valve sticks in the closed position. A third valve in the flow circuit contains a bi-metallic element. This valve assures that rear-drive engagement is consistent over a wide range of ambient temperatures.

Special measures were taken to avoid unnecessary all-wheel-drive engagement when the VUE's space saver spare is in use. Because the spare is slightly smaller in diameter than a regular tire, its installation causes a driveline speed differential that would normally prompt PCA engagement. That circumstance is avoided by prohibiting engagement until the front-to-rear speed differential exceeds 60-80 rpm. As a result, VUE stays in the front-drive mode until extra traction is needed - even when the spare is installed.

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