2008 Astra's Precise Driving Experience Has European Roots and Was Fine-Tuned in America

The Saturn Astra's driving experience was born on the demanding mountain switchbacks and high-speed motorways of Europe, but fine-tuned in the United States to suit North America's unique driving conditions. It is a driving experience characterized by direct, linear steering that complements exceptionally precise handling and smooth ride traits. In short, it engages the driver with exceptional connectivity to the road.

The Astra offers technologies that support its agile yet comfortable driving experience. StabiliTrak – GM's electronic stability control system – with traction control is standard on three-door Astra models, and available on five-door models. The system works in concert with standard four-wheel, anti-lock disc brakes to help the driver maintain control during adverse road conditions or during sudden emergency driving situations.

"Developed in Europe, the Astra's driving dynamics were tuned to perform on narrow, twisting roads," said Jürgen Schöwer, control systems project leader. "At the other end of the performance spectrum, it was also designed to perform on Germany's famous autobahn expressways, where stability and a confidence-inspiring driving feel are imperative."

Adding to the Astra's nimble feel is a robust powertrain. The standard combination in all models is the 1.8L Ecotec DOHC four-cylinder engine and a five-speed manual transmission. The Ecotec engine is enhanced with variable valve timing to optimize power output and fuel efficiency. A four-speed automatic transmission is optional on all models.

Body Structure and Suspension Systems

The foundation for Astra's precise, nimble feel is a body frame integral (BFI) structure that is among the strongest and stiffest in the segment. Overall structural frequencies include first bending and first torsional frequencies of 40.6 hertz (Hz) and 36.2 Hz, respectively.

The body structure is the primary enabler for suspension tuning that delivers a heightened feeling of solidity, stability and driver control – all built around dimensions that include a long, 102.9-inch (2,614 mm) wheelbase and front/rear tracks of 58.6 inches (1,488 mm). The suspension system comprises a MacPherson strut design in the front and a sophisticated torsion beam axle in the rear. Gas-charged preloaded twin-tube struts and shocks provide quick and controlled responses to road bumps, enhancing the driver's feeling of directness – as does the direct-acting front stabilizer bar, which brings a more immediate feel to steering inputs.

Those steering inputs are handled by Astra's electro-hydraulic, rack-and-pinion steering system. It is standard on all models and provides the solid, linear feel of a hydraulic power steering system, but improves fuel efficiency by operating the power steering pump only when necessary. The system has two available configurations: the standard 15:1 ratio on five-door models and a 14:1 quick ratio (standard on the three-door; optional on five-doors). A standard rake/telescoping feature of the steering column enables the driver to find a “just right” steering position and is a feature not seen on many other competitors.

Additional chassis and suspension features include:

  • Hydraulic engine mounts (with the manual transmission) that are tuned to the engine's torque axis to help reduce noise, vibration and harshness – it's a feature not found on many other cars in the segment
  • Hydraulic damping bushing in the front lower control arms that minimizes steering wheel shake
  • Large subframe bushings that contribute to an isolated driving feel and limit vibrations felt in the passenger compartment
  • The rear axle beam is formed to a double-U shape, which serves as a stabilizer bar
  • Rear-axle control arms with hollow-cast, one-piece integrated wheel carriers that are lighter and more stable than conventional steel examples

The three-door Astra XR is tuned for a higher-performance driving experience and is equipped with a 15-mm lowered sport suspension, 17-inch wheels (18-inch wheels are available), performance-rated tires and the quicker, 14:1 steering system.

Brakes, Wheels and Tires

Larger sized front and rear disc brakes are standard equipment and – along with low-compressibility brake pads and a dual-rate booster – provide excellent pedal feel and outstanding stopping performance.

ABS is standard and is tied into Astra's standard stability control system. It features corner braking control that helps neutralize oversteering when braking in a curve – a direct example of the Astra's German-bred driving characteristics that provides a more composed, confident feel on winding roads.

Five-door Astras come with standard 16-inch wheels, but can be upgraded to 17-inch aluminum wheels. Three-door models come standard with 17-inch aluminum wheels, which can be upgraded to 18-inch aluminum wheels and performance tires.

Powertrain

The standard powertrain combination in all models is the 1.8L Ecotec DOHC four-cylinder engine and a five-speed manual transmission – a four-speed automatic is available. The Ecotec engine is enhanced with variable valve timing to optimize power output and fuel efficiency, delivering 138 horsepower at 6,300 rpm and 125 lb.-ft. of torque at 3,800 rpm.

To deliver its powerful, efficient performance, the 1.8L Ecotec engine uses several state-of-the-art technologies, including variable valve timing and four valves per cylinder. Highlights include:

  • Two continuously adjustable camshafts (DCVCP — Double Continuous Variable Cam Phasing) to optimize the charge cycle
  • A two-step intake manifold with a rotary sleeve – instead of flaps – to minimize flow losses
  • A highly efficient oil/water heat exchanger
  • A map-controlled thermostat
  • A deep drawn exhaust manifold with dual integrated catalytic converters

Unlike conventional engines, where the crankshaft and camshaft are mechanically linked in a fixed crank angle (CA) via a toothed belt or a chain, the 1.8L Ecotec engine allows the intake and exhaust cam to twist relative to the crankshaft. This is continuously varied on the engine using an extremely compact, lightweight hydraulic vane-type phaser. The variable range is 60 degrees of CA on the inlet side and 45 degrees of CA on the outlet side – and, depending on the engine's speed and operating conditions, the valve timing can be selected for optimum performance or fuel consumption.

Advantages of the double camshaft adjustment include higher power output and torque characteristics over a wide engine speed range due to optimized cylinder charging; reduced exhaust emissions thanks to high exhaust gas recirculation rates; and reduced fuel consumption. In fact, the 1.8L Ecotec offers 90 percent of peak torque from 2,200 to 6,200 rpm. It also delivers power output of 76 horsepower per liter, making it one of the most powerful engines of its size.

The Ecotec engine family is used in GM vehicles around the globe, including European versions of the Astra. Each has distinct performance and hardware characteristics, but all share a basic construction that includes:

  • Dual overhead camshafts (DOHC) and four valves per cylinder
  • Extremely compact dimensions and low mass
  • Direct mounting of all accessories to the engine structure to eliminate common sources of noise, vibration and harshness
  • Full-circle transmission attachment is more rigid than most four-cylinder powertrains, for reduced noise and vibration
  • GM Oil Life System for optimum oil change frequency
  • Innovative cast-in oil filter housing eliminates crawling under the car to perform oil changes. The design also eliminates throwaway oil-filter "cans" that retain used oil and typically end up in landfills.

The Astra's 1.8L engine also features:

  • Cam phasers for both intake and exhaust valves.
  • Individual coils on each spark plug
  • All-digital sensors
  • Piston-cooling oil jets

Backing the 1.8L Ecotec engine is a standard five-speed manual transmission or an available four-speed automatic. The Aisin automatic is an electronically controlled unit that features fuel-saving automatic Neutral Idle technology. With it, the transmission shifts into neutral at stops, eliminating torque converter drag on the engine. The four-speed automatic also features Performance on Demand, which immediately initiates a downshift at wide-open throttle to provide more immediate response.

Source: Saturn

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