An exceptionally strong structure enables the smooth ride, precise handling and quiet driving traits of the 2008 Cadillac CTS. It’s a stiff structure that builds off the strength of the previous-generation model, which was renowned for its solidity, with strategically placed enhancements that help provide better crash protection, a sharper driving feel and improved noise, vibration and harshness (NVH) performance. 

The elements that comprise CTS’ structure can be divided into two categories: structural enablers and acoustical enablers. The components of the structural category primarily make up the car’s unitized body frame and give it strength, while the acoustical enablers, while also serving to reinforce the vehicle’s rigidity, work more to suppress, absorb or deflect NVH-inducing elements.

Structural enablers

Magnesium instrument panel structure – The instrument panel’s (IP) lightweight magnesium structure is a single-piece, cross-car structure that is carefully sized and mounted to bolster both side-impact and frontal crash performance. Its design provides exceptional stiffness that also helps reduce NVH that can be transmitted through components attached to the IP, such as the steering wheel and steering column. In fact, the steering column registers an outstanding 36.5 Hz frequency during driving.

Cross members – The underbody of the Cadillac CTS is equipped with seven cross members made of fabricated steel that are integrated into the floor pan, on either the top or the lower side of the floor pan. The first cross member is a three-piece structure that is designed to help support the overall load, manage crash energy and, as it is braced against the dash, contribute to the vehicle’s overall stiffness.

Other cross members have been revised or redesigned compared to the previous-generation model, to help improve side-impact crash performance. Changes include:

The second cross member is larger and thicker and includes a bar extension for improved load transfer

The third cross member’s thickness is increased, as has the thickness of its extension; also, the cross member itself is made of high-strength steel

The fourth cross member, located behind the rear Seat area, is significantly enhanced with 1.8mm dual-phase steel end caps that strengthen the load path during side impacts. The center section has a “bar doubler” made of 1.8mm Martensite steel, the highest-strength steel available

The other cross members have been enhanced with various methods, such as the use of reinforced brackets and heavier-grade steel

Octagonal engine rails – To enhance high-speed offset crash performance and occupant protection, octagonal motor rails are used for the front zones of the Cadillac CTS, as the octagonal shape is highly efficient for energy absorption for a given mass. This thinner, lighter steel results in reduced mass yet provides proper energy absorption and reduces passenger compartment intrusion.

Longitudinal skid rails – Another enhancement is the use of longitudinal rails that are lengthened and extend rearward to the four-bar cross member, enhancing overall crashworthiness, NVH and ride and handling. Two high-strength steel under-floor rails run from the front of the dash to the floor pan. They are also injected with structural foam, which helps maintain geometry during a crash while also enhancing stiffness and helping to prevent intrusion around occupants’ feet.

Rocker panels – Exceptionally strong Martensite steel is used on the inner and outer rocker panels to enhance occupant protection in a side-impact crash. The rockers house 2mm structural bulkheads positioned at the second, third and fourth cross member locations. Additionally, an offset reinforcement runs from the A-pillar to the B-pillar, adding bulk to the lower structure for added protection during side-impact crashes.

Reinforced tunnel – A tubular, U-shaped “strap” was added to the Cadillac CTS’ center tunnel, adding tension compression that enhances overall stiffness. It also helps reduce vibration to the floor pan and rear-seat area. A constraint layer – a sandwich of inner and outer steel structures – in the tunnel section helps deaden the transfer of noise into the passenger compartment.

Dual-phase steel rear rail inner sections – Enhancements designed to bolster the rear rail structural section include new inner rails made of high-strength dual-phase steel; the use of structural nylon blocks within the fifth cross member and reinforcement of the torque boxes and rear rails with dual-phase steel.

Upper structure – The high-efficiency upper body structure of the ’08 CTS is all-new and carries a host of material and design applications that enable the vehicle’s outstanding side-impact and roof-crush performance. They include:

Reinforced “dogleg” area

Application of high-strength steel in the B-pillar

Roof rail inner and outer reinforcements made of high-strength steel

Sail panel and windshield outer section design contribute to the CTS’ safety cage strength

A double-header application of high-strength steel that runs across the top forward roof section between the A-pillars.  This enables the 2008 CTS to meet 2010 roof crush requirements in North Americaand enhances side-impact performance

Acoustical enablers

To ensure optimal sound quality inside the CTS’ cabin, a team of noise and vibration engineers used a sophisticated sound recording device, called "Aachen Head" (pronounced AH-KIN), to record sounds inside the vehicle under real-world driving conditions. The Aachen Head is a digital recording tool that closely matches the way humans process sound by preserving the binaural attributes of the sound inside a moving vehicle.

As a result of this extensive and careful testing, the 2008 CTS is expected to be one of the quietest, most acoustically refined sedans in the industry. In fact the CTS has an outstanding acoustic sensitivity of only 2 decibels (dB) from chassis source and an equally impressive wind noise rating of 36 dB.

Elements that contribute to the CTS’ quiet performance:

Laminated front-of-dash – A laminated front-of-dash section uses a sandwich of materials, also known as quiet steel, to reduce the transfer of engine compartment noise into the passenger compartment. The sandwich – two sheets of steel held together with a composite adhesive – damps noise transfer by 3 dB when compared with a conventional dash panel.

Front-of-dash mat – A thick, 28mm front-of-dash mat made of cast foam effectively reduced powertrain noise into the cabin. That mat works like a noise-dampening blanket on the engine side of the dash panel and is applied with a glove-like fit that closes out all cavities in the panel.

Chassis-to-body structure interfaces – Enhanced body structure impedance at the chassis attachment points is achieved with redesigned chassis-to-body structure interfaces. The interfaces are stiffer, which reduces the transmission of low-frequency noise.

Six-point front cradle – The engine cradle, which is solid-mounted to the engine rails for a precise feel, is exceptionally stiff, minimizing NVH and enhancing handling and crashworthiness. The cradle has six attachment points – two more than most comparable sedans – to better handle heavier drive loads and energy pulses, such as those in vehicles equipped with the 3.6L direct-injection engine.

Engine mounting – The engine mounts are hydraulic and have been moved forward and outward on RWD models to lower the load in the mounts, thereby providing more isolation.

Rear cradle – A new rear cradle is stiffer and more isolated to reduce low-frequency resonances in the rear passenger compartment area. The cradle is isolated with four, large complex rubber mounts that provide soft characteristics in fore/aft movements, yet are laterally stiff. As a result, the mounts provide flex over bumps and holes and remain stiff in cross-vehicles dynamics.

Constraint-layered shock towers and wheelhouses – To attenuate noise transfer from the shock towers and wheelhouses, they feature constraint layers comprised of sandwiched metal and noise-absorbing material. In the shock towers, two pieces of metal sandwich around a rubber viscous material. The viscous material creates a noise-absorbing barrier, significantly reducing the noise level in the passenger compartment. The wheelhouses use sandwiched layers of steel.

Cabin sound deadening – Numerous methods are employed to reduce noise in the CTS’ cabin, including the use of lightweight damping material that absorbs high- and mid-range frequencies, the application of thicker, 16-ounce carpet and the use of expandable acoustic foam in body cavities such as the A-pillars, B-pillars and rockers.

Powertrain noise abatement –Engineers developed a host of methods to reduce or eliminate powertrain noise of the ’08 CTS, particularly in models with the 3.6L direct-injection engine, the spark ignition of which can cause a rapid clicking noise due to the high-pressure fuel system. The powertrain noise abatement elements include:

Full-perimeter hood seal

Under-hood sound-damping fiberglass blanket

Engine compartment side curtains

Sound-deadening cover for the high-pressure fuel pump (direct-injection models)

Two-piece engine cover

Isolated fuel injectors (direct-injection models)

Large, noise-canceling “belly pan” at the front underside of the vehicle

Other details contribute further to CTS’ quiet performance, including noise-absorbing trunk acoustic material, structure-less windshield wipers that eliminate “chatter,” and triple door seals.