Exceptional overall stiffness
Advanced structural steel applications
Outstanding acoustic performance
Fine honed craftsmanship
The appearance of the new Chevrolet Sonic immediately conveys an impression of refined quality. In execution the basic structure, build quality, acoustic characteristics, and fine-honed attention to detail place the Sonic at the top of its class.
The new Sonic features a body-frame-integral (BFI) structure based on General Motors new global front-wheel-drive small vehicle architecture. Thanks to a number of holistically designed structural enhancements that mixes and strategically positions advanced steels where they provide the most structural benefit, the new Sonic has chassis stiffness and torsional rigidity ratings that are amongst the best in the global small car segment.
More than 60% of the lower structure of the Sonic and 50% of the upper body is constructed using high-strength or advanced high-strength steels. Most notable is the application of dual-phase bake hardening, and press-hardening steels in the strategic B-pillar, front header, side rockers, and rear bumper areas. Optimal strength in these areas is fundamental to achieving a 5-star Euro NCAP safety rating, as well as providing the structural strength to support 4,2 times the vehicle weight in the event of a roll-over.
It is notable that the strength of special steels used on the Sonic’s predecessor ranged in tensile strength from 340 to 550 MPa whereas the latest generation steels regularly reach 1000 MPa or higher. The use of these advanced materials imparts numerous benefits.
One of these is the solid sporty feel of the Sonic, a product of lighter and stiffer structure. This provides occupants with a heightened sense of stability, safety and confidence set to challenge the very best in the global small car segment.
Another benefit is the acoustic performance of the Sonic, both inside and outside the vehicle. The stiffer structure of this new model makes it easier for engineers to isolate and tune-out powertrain, road and wind noise to create a pleasant environment inside the vehicle. With a focus more on sound quality than on sound level, a team of acoustic engineers fine tuned both the interior and exterior sound qualities of the Sonic. Their success can be measured by the low wind noise rating of just 40,5 decibels and an articulation index rating – a measure of speech intelligibility in continuous noise – of 77% at highway cruising speeds. Both these sound characteristics place the Sonic up with the best in its class.
Enablers that contribute towards the excellent acoustic performance of the Sonic include:
• The use of thicker glass than would be expected for the front windscreen, side windows and rear hatch.
• Front dash mats: the front of the dash panel is sandwiched between two damping mats, specifically tailored to available powertrain packages, to inhibit the transfer of noise, vibration and harshness (NVH) into the cabin.
• A formed resin/felt blanket under bonnet liner provides an effective insulator for noise that might otherwise pass through the windshield.
• Pliable rubber seals along the bonnet lines and between the rear edge of the bonnet and air induction panel ensure a snug and well crafted solution for further noise reduction.
• The use of baffles to inhibit the transfer of airborne noise through hollow structures in the vehicle. These are moulded to fit in specific areas and applied in conjunction with an adhesive foam that expands to provide an effective sound seal when the body passes through the paint ovens during manufacture.
• A three-layer polyethylene/felt substrate is used for the headliner in conjunction with a two-layer soft-touch polyurethane skin.
• A pre-formed carpet module that incorporates a composite backing is used in the Sonic. This solution provides an excellent fit between carpet and floor negating any incidence of floor panel resonance being transferred into the vehicle.
• Melt-on damping pads are strategically applied in the body shop prior to painting. These melt onto the body structure as the vehicle is baked in the paint ovens. The melt-on process ensures that the pads adopt the true form of the panel they are applied to for a superior damping quality.
• All doors incorporate a dual layer sealing system. Secondary seals are mounted to the doors rather than the body for better aesthetic appeal.
• The rear of the vehicle, primarily the area around the rear cargo area, benefits from a number of sound absorbing treatments to insulate this often problematic area.
• Extensive sealing is applied throughout the body. The latest technology sealants provide excellent protection in the most hard to reach areas and enable even pin-holes of light to be eliminated. The specific attention to sealing of all joints effectively to prevent any ingress of light, noise, moisture, or outside contaminants is a major development in the build of the new Sonic.
• All four door handles are braced to provide a solid sound when they are depressed to gain entry to the car.
• Composite wheel arch liners are fitted at all four corners to assist in damping out road noise, particularly on rough surfaces.
• The intake and exhaust of the Sonic Hatch have been tuned to provide a pleasant, muted acoustic characteristic.
• Hydraulic powertrain mounts are utilised to assist in damping NVH transmission into the interior of the vehicle. This together with the engine-to-cradle mounting system results in exceptional powertrain isolation for a level of refinement not usually associated with a small car.
• The use of so called “flat” wiper blades assists in reducing wind noise by as much as one decibel. A characteristic of these blades is that they are devoid of any rigid support structure but rather have an aero shaped rib that runs along the top surface of the blade. The blades are aero tuned to the windshield shape for a lower profile and superior contact with the windshield.
Other refinements evident in the new Sonic include the use of some 10 percent more spot welds in the body structure that on the previous model. This results in added rigidity for the body and improved durability.
All secondary surfaces, for example the areas around the door frames, exposed when one is getting into or out of the vehicle, have been enhanced for a flush, well finished appearance. This has been achieved through the adoption of advanced welding techniques that ensure a better surface finish and through the use of minimal sealant between sheet joints without any compromise to corrosion resistance.
Interior and exterior element-to-element gaps and flush fitting relationships have been refined to a point that they represent the best quality in the segment according to General Motors’ strict internal benchmarking procedures, procedures that are designed to place GM products at the forefront of build quality in every segment that the company competes in by 2012.
The body sides are now single piece pressings for the interior and exterior components that extend from the front door pillar right through to the end of the rear quarter panel. This largely eliminates joints and promotes consistency of build and sealing especially in the door and window glass areas. The overall impression derived from this is one of a tight exterior with excellent panel fit. Door-to-door, door-to-fender, bonnet-to-fender, and lamp-to-fascia gaps are all 3,5mm or less.
Quality has been the key word for the new Sonic right from the design stage, through the engineering process and on into the volume production phase. This new small Chevrolet has positioned itself to set new quality benchmarks in its market segment.