On the 2016 Cadillac CT6: The Flagship

The 2016 Cadillac CT6, the flagship product for the brand.

The 2016 Cadillac CT6, the flagship product for the brand.

Although the vehicle is large, according to Travis Hester, executive chief engineer for the vehicle, at 3,657 pounds, it is nearly 1000 pounds lighter than midsize European sedans and 1,000 pounds lighter than the lightest Mercedes S-Class. This is accomplished, in part, through an aluminum-steel body structure made posssible by a proprietary welding technique, as well as through the deployment of highly engineered castings.

One of the three engines available is a 3.0-liter twin-turbocharged V6 that features active fuel management (a.k.a., cylinder deactivation) and engine stop/start technology. It also produces 404 hp and 400 lb-ft of torque. It is mated to an 8-speed automatic.

Inside the car, the design is one that is meant to emphasize spaciousness.

Johan de Nysschen, president, Cadillac, is no stranger to the luxury segment of the business. Not by a long shot. Prior to joining the General Motors division in July 2014, de Nysschen was president of Infiniti Motor Company. Before that, he was the president of Audi of America, which was preceded by five years as president of Audi Japan.

This resumé certainly indicates that de Nysschen has a more-than-ordinary understanding of both the Asian and European approaches to luxury vehicles, and it is his mission to make Cadillac a name that is mentioned in the same breath as the best builders in the world.

He seems pleased with the way things are going for the brand, which he characterizes as being “resurgent.”

He says that the vehicles are demanding better transaction prices (people are buying “richly specified” vehicles), and they are “restoring good balance” to the inventory (meaning that you don’t have an array of unsold cars and trucks sitting on dealer lots, which leads to the need for deals and discounts, making the brand less prestigious as a result). Cadillac is also attracting younger buyers than has been the norm and many of the customers—more than half in 2015, de Nysschen points out— are new to the brand.

The lineup of cars that Cadillac has had on offer are the compact ATS, the midsize CTS, the large(r) XTS and the hybrid ELR.

The ATS and the CTS are based on the Cadillac Alpha platform. The XTS has the same platform as the Chevrolet Impala. The ELR is a variation on the Chevrolet Volt.

Heretofore the brand has been lacking what de Nysschen calls a “large, luxury sedan.”

Enter the CT6, which is based on an all-new, Cadillac-exclusive platform, Omega.

De Nysschen doesn’t hesitate to point out that they are launching this car in the space where the Mercedes S-Class, the BMW 7-Series and the Audi A8 reside.

It should be noted that in many ways the existence of the CT6 is predicated on the company proving that it can provide a product that goes back to its “Standard of the World” slogan. That is, this “flagship” is being launched into a segment that is exclusive even in the context of the number of people who are buying or leasing the vehicles. That is, according to Autodata, in 2015 there were 19,049 S-Classes delivered, which is down 21 percent from 2014. The 7-Series, at 9,292, was off 4.6 percent. The A8 saw 4,990 deliveries, off 15.5 percent. Clearly, this isn’t about big volume, but an incremental advance to Cadillac’s performance in the U.S. market.

However, it should be underscored that this is a vehicle that has been developed with the China market in mind, as well, and it is also going to find its way to Europe. (The car is being manufactured at the GM Detroit-Hamtramck assembly plant, as well as a plant in Shanghai.)

But it is less about numbers than about showing that Cadillac is able to design, engineer and deliver a car that is not merely equal to but better than any in the world.

Or as de Nysschen puts it, “We aren’t going to lead the charge by following.”

According to Travis Hester, executive chief engineer for the Cadillac CT6, vehicle development was predicated on four pillars:

1. Appearance.

2. Size.

3. Driving dynamics.

4. Acoustics.

We’ll get to the appearance shortly.

In terms of size, the CT6 measures 204 inches long, 57.9 inches high, 74 inches wide, and has a 122.4-inch wheelbase. Hester points out that while it is slightly less long than the S-Class, 7-Series and A8 (e.g., the S-Class is 206.5 inches long), it weighs significantly less than its competitors. Again, to use the S-Class for an example, a 2016 S550 sedan has a curb weight of 4,630 pounds.

Yet through some exceedingly clever engineering that Hester and his team executed, largely though the deployment of finite element analysis and other computer-aided engineering (CAE) tools that allowed precise modeling of structures and the appropriate materials for those structures, the CT6 weighs much less. The curb weights for the car are:

• 3,657 pounds with a 2.0-liter turbo and rear-wheel drive (yes, a four-cylinder engine).

• 3,926 pounds with a 3.6-liter V6 and all-wheel drive.

• 4,085 pounds with a 3.0-liter twin-turbo and all-wheel drive.

In fact, Hester notes that the CT6 is lighter than the cars in the class below it—the E-Class, 5-Series and A6. (E.g., the curb weight of a 2016 E350 4MATIC sedan is 4,211 pounds.)

While one might think that this light weight is achieved through the use of an aluminum structure, that’s not the case. At least not entirely the case.

Rather, the body-in-white (BIW) is a mixed-material construction, consisting of 62 percent aluminum alloys and 38 percent steel alloys. Hester explains that one of the enablers of the construction of this structure is a development that came out of the GM Research & Development operations a few years ago, which is a spot welding process that uses a patented multi-ring domed electrode that permits the welding of aluminum to steel.

Overall, there are 3,073 spot welds on the BIW. There are 268 meters of structural adhesive.

Hester says that it would be easy to do an all-aluminum structure, one where it is a matter of joining like to like. But he notes that the mixed approach is “the best way to design a car.” He points to a section of the floor panel. He admits that were they to make it an aluminum component, it could be 1- to 2-mm thick. The steel part that they’re using is 1.6-mm thick. He comments that they also have to take other issues into account, like noise, and if they were to use the aluminum, they’d need to use acoustic material from 60- to 70-mm thick to attenuate the noise, whereas it is merely 15 to 20 mm thanks to the steel.

Hester is also quite bullish on the use of highly engineered, large castings in the construction of the CT6. For example, he cites the front body hinge pillar, which runs from the bottom of the A-pillar to the center of the front wheel. This, he says, usually consists of 35 stamped parts that need to be welded together. However, they are able to do it with a single large casting. Cadillac has designed the casting so that there are differences in thickness to provide strength where needed and as needed. The face of the casting is like an egg-crate were the crate to consist of rectangular pockets rather than circular ones. Hester points out that while it is “easier in math models to draw straight lines,” the pockets have curves as that was determined to provide more strength. What’s more, the edges of the pockets are scalloped, not straight, in order to provide weight reduction.

Overall, they’ve calculated that the BIW has 20 percent overall parts than would otherwise be required. What’s more, according to Hester the CT6 is stiffer than both the Cadillac ATS and CTS and it is the “quietest Cadillac ever produced,” (point 4).

The weight savings achieved goes to the third point, “driving dynamics,” as it contributes to better handling and a power-to-weight ratio. As previously noted, all-wheel drive is available. There is also magnetic ride control, which is based on the use of a magnetic rheological material that quickly reacts to road inputs, the degree to which is selectable as there are Tour, Sport and Snow/Ice modes. Bill Mack, global product manager, points out that the performance modes not only adjust the response of the ride control but the throttle progression, transmission shift mode and all-wheel drive settings.

It also adjusts one more thing: Active rear steer. This contributes to not only better handling during high-speed maneuvering, but also allows what is a large car to have a comparatively small turning circle (37 feet), which is certainly helpful in parking lot situations. In the parking lot scenario, the 
rear wheels can go 3.5 degrees off-angle. At high speeds, the rear wheels go in-phase 2.75 degrees, which helps keep the car from having to “pull” the rear, as in lane-change maneuvers. 

Which brings us around to point one. According to Taki Karras, Cadillac exterior design manager, “We told the team to design a car that looks as lightweight and agile and athletic as the architecture promises.” He adds: “The car cannot look cumbersome or heavy or bulky.”

Karras says that they worked with engineering on achieving the look that they felt was essential to deliver the overall message. For example, he points out that the aforementioned front body hinge pillar casting allows a better body-to-wheel relationship (the sheet metal is close to the tire) and a low, wide stance for the vehicle.

“We were able to take our Cadillac signature lamps and pull them rearward in the car and have a very small distance of body color between the lamp and the front tire. When you look at the car in the rear three-quarters, the wheel becomes the thing that is the most dominant.” This, he says, makes the car really look planted to the ground.

“Because the engineering team was able to lower the height of the hood, we were able to make the car look wider,” he says. In addition, the design of the grille emphasizes width over height, Karras says.

“On the rear it is recognizable as a Cadillac,” but he points out that the rear lights are tipped in a bit and have a hockey stick shape along the bottom. “It is a little thing, but it speaks to designing something that is supplicated, refined and simple. We wanted this car to have a level of restraint because it would have a longer-lasting appeal than if it was something adorned with styling cues that made it a loud design.”

On the inside, they’ve gone away from a dominant center stack to something that is more broadly horizontal across the car, emphasizing space. Yes, there is a 10.2-inch diagonal CUE interface screen with 1280 x 720 HD resolution and a console-mounted touchpad, but this vehicle isn’t like a jet fighter in having a cockpit-style layout.

Which brings us back to de Nysschen. He acknowledges that there is a market shift in automotive buying preferences to crossovers. “Many people,” he says, “have asked why build another large sedan? Because the sedan market is where you build your reputation. And the CTS represents the pinnacle of engineering, technology and the state-of the-art.”