VW Eos: hats off; The German automaker joins the folding hardtop brigade with a vehicle that is part golf, part Passat, usable, and sporty.

Folding hardtops are becoming as common as iPods these days. Ford's 1957-1959 Fairlane Skyliner took technology originally developed for the Continental Mark II to production, but the complex and heavy mechanism never caught on. Years later, the idea was revived by the folding roof of the Mercedes SLK, and found its way into everything from the extremely rare Qvale Mangusta to Cadillac's XLR, before targeting more affordable offerings like Volvo's C70 and Pontiac's G6. Now VW enters the fray with its Eos, a Golf-based four-seater that adds a few tricks of its own to the mix.

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The Webasto-supplied top comprises 470 components, including a 40-amp electric motor driving a radial piston pump at 160 bar that sits in an acoustic capsule behind the spare tire. According to Heiko Nause, an engineer on the Eos program, "Pressing the top button activates four pairs of hydraulic cylinders that activate two four-link mechanical systems--one driven by a six-piece gear mechanism, and the other an eight-piece gear mechanism--that are responsible of the top kinematics." The roof mechanism weighs approximately 49 lb., though the complete roof assembly weighs 187 lb; lowering it transfers 132 lb. of that weight rearward. Part of the mass (26.5 lb.) comes from the addition of a large tilt/slide sunroof panel that is 44.3-in. wide, 24-in. long, and can be tilted 1.5-in. It is the first time an opening sunroof has been integrated into a folding hardtop. In addition, 12 Hall-effect sensors monitor all roof movements, while the top ECU monitors 250 parameters. VW says the top--which stores under an Inapal-supplied double-wall trunk lid that weighs 17 lb. and is capable of supporting two 165-lb. people sitting on it--has such a compact arc that it can be lowered in the average garage, though that is not recommended. Trunk space with the top down is 6.6 ft[.sup.3], and the rear seat pass-through--good for stowing skis--can be used top up or down.

One problem all convertibles face is retaining structural rigidity. VW claims a first-mode torsional rigidity of 23.5 Hz for the Eos body-in-white. This comes from the use of high-strength steel, the shape of the side sills, an aluminum front reinforcement that connects the subframe and longitudinal front rails, and diagonal struts on the rear subframe. Hot-stamped ultra-high-strength steel is used in the A-pillars, seat cross member/B-pillar supports, and floor cross members. The Eos body contains 189-in. of laser welding (the majority in the door openings), 59.6-in. of MIG welds, 71.2-in. of low-temperature MAG (Metal Active Gas) welds, 18.9-in. of plasma welds, and approximately 4,500 spot welds. Lasers are used for dimensioning purposes, too: to set the door/front fender gap, and to measure 24 points on the body-in-white.

According to Nause, the front of the vehicle--powertrain, basic underbody structure, suspension--comes from the current Golf/Rabbit, while "the rear suspension is borrowed from the Passat because of the greater weight of the Eos." Another advantage of the Passat rear suspension is that the four-link axle is acoustically decoupled from the body, reducing the sound paths coming into the body. "A lot of the components are shared with other vehicles in the VW lineup," says Nause, "but the chassis and roof are unique to the Eos." The basic Eos chassis will be carried over to the 2008 Scirocco sports coupe.

Base vehicles--the least expensive Eos starts at $27,990--are powered by VW's turbocharged, direct injection 2.0-liter inline four, which is good for 200 hp and 207 lb-ft. This is enough to push the Eos from 0 to 60 mph in a claimed 6.4 seconds with the standard six-speed manual transmission. A six-speed DSG dual-clutch automatic is optional with the four, but standard with the 3.2-liter, 250 hp V6; the same basic narrow-angle (15[degrees]) V6 found in the Touareg SUV, and not the larger (3.6-liter), narrower (10.6[degrees]) V6 introduced last year in the Passat. The V6 Eos starts at $36,850.

By Christopher A. Sawyer, Executive Editor