Cadillac fortifies CTS for V duty

  • 11-Sep-2015 10:36 EDT
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Cadillac took its CTS-V sport sedan challenger to Road America to prove the car's on-track prowess.

Cadillac continues its battle to achieve premium market esteem equivalent to that of segment leaders BMW and Mercedes-Benz by pushing for top quality and performance in each new model. The high-performance CTS-V is meant to put a stake in the ground, demonstrating Cadillac’s seriousness and, to do that, the car is upgraded from the standard CTS in nearly every respect.

Visually, the changes start with the bodywork, which includes a lightweight carbon-fiber hood and revised front and rear fascias, fenders, rear spoiler, and rocker moldings. An optional carbon-fiber aero package adds a front splitter, enlarged wing, diffuser, and carbon-fiber air extractor on the hood. Enlarged intake openings and less obstructive grille mesh contribute to a 50% increase in airflow through the front of the car to its array of six heat exchangers.

“Every exterior detail earned its way onto the car for its aerodynamic function,” stated Product Director Hampden Tener. Aerodynamic effectiveness is critical because the CTS-V is the fastest Cadillac ever; top speed is 200 mph (322 km/h) and it rockets from 0 to 60 mph (97 mph) in 3.7 s.

Those flared fenders spread to cover the 19 x 9.5 in front and 19 x 10 in rear wheels. These aluminum wheels are 45% stiffer than those used on the previous-generation CTS-V for more precise steering control.

They mount Michelin Pilot Super Sport summer-only performance tires: 265/35ZR19 in front and 295/30ZR19 in the rear. As with the ATS-V, these custom-tuned Michelins feature three distinct rubber compounds in the tread, with a hard outer shoulder, grippy inner third, and a rain-optimized center section.

Inside the wheels are Brembo brakes with staggered six-piston front calipers and four-piston rears. The rotors are a two-piece design, with a lightweight aluminum center section and cast iron friction surface. The 390 mm (15.4 in) diameter fronts are 365 mm (14.4 in) rears are treated with a ferritic nitro carburized process for corrosion resistance. Customers can choose among three available matte-finish colors for the calipers.

At the rear, the CTS continues with a five-link independent suspension arrangement, while the front McPherson strut setup enjoys dual lower ball joints and a direct-acting anti-sway bar for more precise control. These zero-compliance ball joints, stiffer springs, and a stiffer anti-roll bar combine to provide a 20% increase in roll stiffness compared to the traditional elastomeric bushings.

Wheel motion is controlled by BWI Group magnetorheological shock absorbers, the one-time MagnaRide technology, now in its third generation. A 40% faster response time than before lets the CTS-V respond to changes in the road surface every inch the car travels at 60 mph.

A ZF Steering Systems Servotronic II variable-ratio electric power steering rack has 14% greater system stiffness for improved steering feedback and precision.

Underpinning all of these moving parts is a chassis that is reinforced for a 25% increase in stiffness compared to regular CTS models. Upgrades include a shock tower-to-tower brace, a shock tower-to-plenum brace, V brace for the engine compartment, strengthened rocker bulkhead, stronger braces between the rear suspension cradle and the chassis rocker area, and braces from the upper tie bar to the rear bumper. Additionally, a bolt on 25 mm (1 in) thick aluminum panel connects the front cradle to the chassis more securely.

With all this reinforcement, bigger brakes, and enlarged heat exchangers, the CTS-V’s 4145-lb (1880-kg) curb weight comes in 100 lb (45 kg) lighter than that of the previous car.

 

The CTS-V’s powerplant is General Motors’ supercharged overhead valve 6.2-L aluminum block LT4 V8 producing an SAE-certified 640 hp (477 kW) at 6400 rpm and 630 lb·ft (854 N·m) of torque at 3600 rpm. Cadillac notes that these numbers top those of rivals like the 577-hp (430-kW) Mercedes-Benz E63 AMG or the 560-hp (418-kW) BMW M5. Cadillac predicts the CTS-V will achieve U.S. EPA fuel economy scores of 14 mpg city and 21 mpg highway.

As with the current-generation Chevrolet Corvette Z06, which debuted the LT4 engine, the CTS-V’s powerplant features a smaller-displacement version of the Eaton supercharger, whose smaller rotors’ reduced inertia spin up more quickly under acceleration. The cylinder heads are Rotocast A35T6 aluminum for its greater strength and tolerance of heat.

Power transfers from the LT4 to GM’s Hydra-Matic 8L90 planetary automatic transmission through a reduced-diameter torque converter. Now 258 vs. 300 mm (10.2 vs. 11.8 in) on the previous car, this torque converter’s reduced inertia contributes to the transmission’s ability to execute upshifts in just 150 ms, putting it in the hunt with dual-clutch transmissions for rapid shift times while providing the smooth low-speed driving characteristics expected of automatic transmissions.

The transmission’s shift characteristics, along with control of the magnetic ride control shocks, power steering assist, throttle response, and many other variables, are determined by the drive mode selector. In Touring mode shifts are optimized for smoothness and fuel efficiency, Sport mode prioritizes keeping the engine revving, and Track mode delivers an amazingly correct shift schedule for all-out racing. There’s also a snow mode that is probably better not tested on the standard summer-only Michelins.

The rear differential is computer controlled so it can be totally open or provide peak pre-load torque, if needed, to transfer power to the tire with grip.

Early CTS-Vs suffered axle hop under acceleration, and Cadillac’s solution is to use different diameter axle shafts so that they operate with different resonant frequencies. In this case, the driver’s side axle is 52 mm (2.0 in) in diameter compared to 28 mm (1.1 in) for the passenger’s side.

The car’s fuel tank is also located in that vicinity, and Chief Engineer Dave Leone took the opportunity while pointing out critical bits on a rotisserie-mounted car to mention that prototypes had suffered from fuel starvation at low fuel levels. His team diagnosed the problem by installing a clear gas tank for testing that let them see what was happening inside. Now, owners can hammer the CTS-V around a track at high levels of lateral acceleration (we saw 1.25 g in corners at Road America) with the fuel as low as an eighth of a tank without suffering any fuel-pickup problems, Leone said.

Inside, the CTS-V is fitted with extra leather and unique optional $2600 16-way adjustable Recaro front bucket seats. The available Webasto panoramic sunroof, whose large opening easily lights front and back rows, lend the cabin an airy atmosphere.

As the first 2016 Cadillac to reach showrooms, it also debuts the second generation of the company’s signature CUE touch-screen infotainment and HVAC control interface.

Addressing complaints about the slow, balky performance of the first-generation system, Cadillac has upgraded CUE computing hardware to the Freescale Semiconductor iMX6 processor that, at 4000 million instructions per second, is three-times faster than the original chip. Response time is down to 100 ms, which is within shouting distance of an Apple iPhone’s 80-ms response time, so users will find it satisfactory, reported Leone.

Critically, destination routing in the GPS navigation system is much faster than before, eliminating a key headache. Further, programmers improved the navigation system interface with the simple inclusion of a “cancel” button on the map while the system provides guidance. Previously, drivers had to navigate through three layers of menus to perform this common task.

The center stack display also can now mirror iPhone apps, giving drivers somewhat less distracting access to a few key apps that are enabled for use in the car. Google's Android Auto is also in the works, according to Leone.

The CTS-V also features the built-in video camera and Cosworth data-acquisition system seen previously on the Corvette Z06 and Cadillac ATS-V, letting drivers shoot video of track laps while recording data from those laps that is overlayed on the video for easy viewing. With the Cosworth Toolbox application on a computer, CTS-V drivers can drill down into their data and compare laps or even against another driver’s data to learn speed secrets for faster laps.

Or they can use the data to prove to their friends that the CTS-V is indeed faster than its German competitors.

 

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