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Automotive Industry

Saturn Ion: re-entry vehicle - On Cars

Automotive Design & Production, Nov, 2002 by Christopher A. Sawyer

It's very easy to summarize any Saturn: "A spaceframe vehicle with polymer doors and fenders, horizontal headlamps, a side 'swoosh' character line, and 'Saturn' badges located behind the wheel openings in the front fenders." This also describes the 2003 Ion, which is available either as a sedan or a "Quad Coupe." It's the first nameplate--Saturns now have names, not just alphanumerics--to use GM's Delta architecture. It also replaces the 12-year-old Saturn S, and is a pretty impressive car.

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All Ions sit on a 103.2-in, wheelbase and are about 185-in, long, which gives the sedan 93 [ft.sup.3] of interior space, the coupe 87.3 [ft.sup.3]. For rigidity and superior crash performance, the engine rails are made of high-strength low-alloy (HSLA) steel, the battery is located in the trunk, and the body side is a one-piece stamping whose offal is recycled to create brackets and other items for use elsewhere in the car. In addition, the sedan has two steel beams in the front doors, one in the rear doors, as well as structural foam inserts. The Quad Coupe--so named for its four doors (two full- and two half -size)--use single beams with high-density foam inserts in the front doors, and heavy-gauge steel reinforcements combined with upper and lower latches in the rear doors. The result is a first-order beaming of 27 Hz in the sedan, 23 Hz in the coupe, either side of the 25 Hz most manufacturers claim as their bogey. This is pretty impressive for an entry-level sedan and coupe that have base weights of 2,69 2 lb. and 2,751 lb., respectively.

On the passive safety front, the story is similar. Saturn offers the Ion with standard dual-stage front airbags, front seatbelt pre-tensioners and load limiters, three-point belts at each seating position, and optional side curtain airbags. In order to reduce deployment injuries, the driver's airbag is recessed in the hub of the 340-mm (13.4-in.) steering wheel, and folded so that it deploys radially rather than directly at the driver. The passenger-side bag, on the other hand, initially deploys up toward the wind-shield, expands outward, then toward the front seat occupant. In an impact, a sensing unit ascertains the severity of the impact, fires the seatbelt pre-tensioners, and determines which level of airbag deployment--primary or primary and secondary--is necessary to adequately protect the occupants.

The electrical architecture of the Ion is similarly interesting in that the five to eight (depending on options) microprocessors are linked via a vehicle network, which lessens the amount of wiring, and allows a number of personalization programs to be integrated into the vehicle systems. (BMW followed a similar path with the Mini.) Things like: turning the headlights on when the wipers are activated, controlling wiper sweep in relation to the speed of the vehicle, programmable door lock/unlock modes, turning off the starter motor circuit once the engine fires, preventing the driver's door from locking when the keys are in the ignition, and retaining power to the accessories when the engine is off. "Features like these usually aren't offered in this segment," says senior development engineer Alan storck, "but the Ion's architecture allows hardware and software expandability, which means these functions are essentially free."

Even the engine architecture is common. The Ion uses GM's all-aluminum 2.2-liter Ecotec four-cylinder (often referred to by its L850 designation). It's lost-foam cast, has dual balance shafts, and produces 140 hp at 5,800 rpm, 145 lb.-ft. of torque at 4,400 rpm, with a redline of 6,500 rpm. In future applications-especially the "Tuner Coupe" Saturn launches next year--the engine will be supercharged and its output increased to at least 200 hp. Torque capacity is unknown for this engine variant, but the Getrag F23 five-speed manual gearbox has an input shaft torque capacity of 175 lb.-ft., and peak input speed of 7,000 rpm. The gearbox also has a cable-operated shifter, carbon fiber blocker rings on reverse and third through fifth gears, double-cone sintered bronze blocker rings on first and second gears, and a synchronized reverse gear.

Of course, this isn't the only gearbox available. Sedan owners can opt for an Aisin AF23 five-speed automatic that is shared with some Opel and Saab models: it is a very unusual gearbox for an entry-level car. Quad Coupe buyers don't get this choice, however. They'll have the option of GM's VTi continuously variable transmission (CVT), which is also offered on the Saturn Vue SUV. GM claims the CVT has 45% fewer parts, a fuel economy advantage, and is easier to manufacture than a conventional four-speed automatic transmission. Getting customers used to it will take time, hence the coupe-first roll-out.

Missing from the Ion is a hydraulic power steering pump. Saturn chose a Koyo-supplied electronic power steering unit that is speed-sensitive, has an integrated torque sensor, and is said to provide an fuel savings of 0.7 mpg. "There are five different calibrations for the steering," says Storck, "which correspond to the wheel and tire combinations offered on the sedan and coupe." There are, he admits, three more calibrations available. Storck declined to identify what changes to the Ion's specs would trigger their use.

Automotive Industry

Saturn Ion: re-entry vehicle - On Cars

Automotive Design & Production, Nov, 2002 by Christopher A. Sawyer

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