Cadillac’s 2016 CT6 is a body-engineering benchmark

  • 01-Apr-2015 03:04 EDT
CadillacCT6Reveal01.jpg

While the CT6 launches with three gasoline engines, it will add four-cylinder and V6 diesels from GM’s advanced light-vehicle diesel family, now under development, for Europe within three years.

Cadillac’s all-new 2016 CT6 full-size sedan is big for such a featherweight car. It weighs about 200 lb (91 kg) less than the BMW 5 Series but offers the interior volume of the short-wheelbase 7 Series, thanks to what is arguably the industry’s most aggressive combination of lightweight materials, forming technologies, and new joining methods in a non-exotic sedan.

The CT6 weighs 3700 lb (1678 kg) in base-curb form with 265-hp (197 kW) 2.0-L turbocharged I4 and rear drive—5 lb (2.2 kg) lighter than the smaller CTS. Overall it is a technological tour de force, as competitors will ultimately discover in their first teardown analyses. Its top-line powertrain features a Cadillac-exclusive 3.0-L V-6, SAE rated at 400 hp (298 kW) and 400 lb·ft (542 N·m) and using the industry-first combination of twin turbochargers, direct injection, cylinder deactivation (General Motors’ new system for OHC valvetrains), and stop-start.

Power is delivered to either the rear wheels or all wheels, depending on driveline configuration, via GM’s new 8L45 eight-speed planetary automatic. An automatic decoupling AWD is standard on V6 cars. A new 3.6-L naturally aspirated V6 also is available, and GM’s new family of light-vehicle diesels currently under development will provide four-cylinder and V6 engines for European CT6 models within three years, a GM executive said.

Inside the CT6, a “camera mirror” provides streaming video of 360° front and rear views while driving. GM’s new third-generation night-vision system helps the driver identify people, creatures, or objects in the road ahead using thermal imaging, alerting the driver with a display on the cluster.

Automotive Engineering will publish detailed articles on the CT6’s development and key technologies in the upcoming months.

The new Cadillac proves GM’s commitment to “reinventing the large luxury sedan,” as the brand’s President Johan de Nysschen said at the car’s New York media launch. “Reinventing” translates into putting GM’s flagship brand beyond par with the world’s best in every comparative metric and keeping it there.

According to Cadillac Chief Engineer Dave Leone, and CT6 Chief Travis Hester, development began over four years ago with the aim to create a large (E-segment) rear-drive sedan with class-leading NVH performance offering the driving dynamics of a midsize. Included in the plan was rear-passenger room and interior execution featuring five-way-massaging front seats and reclining heated/ventilated rear seats also with massage. The front seatbacks have integrated and retracting 10-in infotainment screens.

Such lavish attention to comfort, convenience, and detail is expected by premium-vehicle customers in China, one of GM’s production locations for CT6. U.S. production will begin at GM’s Detroit-Hamtramck plant in late 3Q2015.

Lessons learned in body and suspension engineering of the C-segment ATS and D-segment CTS dovetailed with development of GM’s new lightweight Omega vehicle architecture, first deployed on this model. 64% of the CT6 is aluminum, including all exterior panels. The multi-metals body-in-white “is lighter than that of the current Audi A6 and Mercedes E-Class and about 225-lb lighter than if we’d just used our CTS configuration and material set,” Leone noted. The structure uses a carefully tailored mix of aluminum extrusions, 13 HPDC (high-pressure die castings), and high-strength and ultra-high-strength steel alloys (including the floorpan), for specific load-path and other applications.

Highlights of the HDPC components include a large die-cast front body hinge pillar, produced by Cosma. According to Hester, this component’s size and complex geometry posed a challenge “but the Cosma guys really worked hard for us on this and came through,” he explained.

The cast-aluminum hinge pillar “does the job of 35 parts in a traditional hinge-pillar application,” Leone said, contributing to a body-structure that is “super stiff” while reducing the bill of material by 20%. An acoustic laminate panel supplied by Shiloh is used in the critical dash panel location to damp noise into the cabin.

To join the body structure, GM is employing its proprietary aluminum spot- and laser-welding processes—the structure contains 3000 spot welds—together with ample use of self-piercing rivets and “180 linear meters of adhesive bonding,” Hester said.

The CT6 suspension uses a front high-arm short/long arm set up with aluminum control arms and knuckles. In the rear, there’s a five-link, active-steering arrangement with multiple outer ball joints, with steel control arms and GM’s MagneRide magnetorheological damping system available (not standard) on both ends. The system offers selectable drive modes including Tour, Sport, and Snow/Ice.

The new CT6 will ride on a choice of 18-, 19-, and 20-in wheels, with 255/45 tires.

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