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Improvements in all areas of the Concorde and Intrepid provided a quieter, more comfortable ride for all occupants, particularly those in the rear seat. Interior noise level of the new Concorde and Intrepid was reduced by a substantial 3 dB (decibels) compared to their predecessors. The following subjective improvements accompanied this measured reduction:
Both new Concorde and Intrepid engines were engineered to minimize noise generation, leaving less to be dealt with externally. Engine sound remained clearly perceptible, especially under hard acceleration, but the sound was smooth and suggested power.
A major portion of objectionable engine noise was caused by deflection and resonance in structural and dynamic components. To minimize this, components were stiffened and, in some cases, made lighter to impose less force, thereby reducing noise. Power train improvements provided the following noise-reducing increases in stiffness relative to the 1993-97 3.5-liter V-6 power train, which at its introduction in 1993, had the lowest radiated (structural) noise level of any engine ever tested by Chrysler:
Both the new Concorde and Intrepid shared the following additional power train quietness features:
Vibration was reduced by making structures stiffer and moving parts stiffer and lighter. Noise transmission was avoided by preventing outer surfaces from resonating with noises inside the engine-valve train, camshaft drive chains, oil and water pumps, etc.
The 2.7-liter engine provided the following noise reduction features and their associated benefits compared to the former (214-hp) 3.5-liter engine:
Both Concorde and Intrepid shared the following chassis systems quietness features:
An all-new power train/front suspension cradle helped reduce transmission of noise and vibration from the tires, suspension, and power train to the passenger compartment. Like its predecessor, the power train/front suspension cradle mounted to the body structure through four isolators. New, three-piece isolator construction-body, jounce plate, and rebound plate-allows fine-tuning of isolator performance.
Low-friction rubber front stabilizer bar mounts provided smooth, quiet operation throughout the life of the vehicle. Microcellular urethane jounce bumpers and urethane cushions at the top and bottom of each spring reduced harshness and helped minimize noise transmission to the body structure. They were also used in 1997.
A rubber-isolated rear suspension cross member helped reduce transmission of noise and vibration from the tires and suspension. Four tuned isolators block transmission of noise from the transverse suspension control arms, significantly improving rear seat quietness compared to the former structure-mounted control arms. Microcellular urethane jounce bumpers and urethane cushions at the top and bottom of each spring reduce harshness and helped minimize noise transmission to the body structure. They were also used in 1997.
All disc brake rotors cast from damped iron, an alloy metallurgically formulated to ring less than conventional cast iron, reducing the potential for high speed brake squeal that can occur under some operating conditions.
ABS operation was less obtrusive because the new ICU (integrated control unit), which produced a pulsating noise during ABS action and also included a pump, was double-isolated. The ICU attached to its mounting bracket through rubber isolators. The bracket then attached to the power train/front suspension cradle, which was also rubber-isolated from the passenger compartment. Noise transmission was further reduced because the hydraulic unit was farther from the passenger compartment than on prior models.
DMA (digital model assembly) found room for added muffler volume, a major factor in reducing exhaust noise. Conventional rolled construction further reduced noise because the outer shell had less tendency to resonate than did the previous stamped construction. To prevent exhaust noise from being transferred to the passenger compartment, hangers that support the muffler attached to the rubber isolated rear suspension cross member, providing a second level of isolation compared to the previous body mounts in these location. Hangers had improved isolation characteristics.
Two resonators were used with all power trains. A computer program was used to design the muffler and resonators silencing systems and position them at their most effective locations. One resonator was located under the floor and the other just forward of the tailpipe outlet. The muffler was placed transversely beneath the rear suspension cross member-a location proven to be highly effective for noise reduction. The exhaust system for each engine was also individually tuned for quietness while providing a pleasantly perceptible sound under medium to hard acceleration.
Body Seam Sealing
To prevent high-frequency noise from entering the passenger compartment through small, frequently invisible openings in the body, lightweight, expandable body sealer was robotically applied after the bodies are primed. This was Chrysler's first use of 100 percent robotic body seam sealing. The sealer expanded to fill the openings when heated in the paint ovens. Robotic sealing was both accurate and easily adaptable to the unique features of all three body shells. It also applied the precise amount of sealer needed for a neat appearance with no clean-up required. Bodies were designed with the vast majority of openings no larger than 0.08 inches (2 mm) to assure long term sealing effectiveness. Openings over 0.08 inch (2 mm) were covered with foam tape that also expanded in the paint oven, rather than manually applied bulk sealer used previously, which was hard to apply consistently, and may fall out in time.
Air conditioning compressor quietness resulted from the findings of a 2-1/2 year benchmarking study and functional redesign. Reducing internal compressor tolerances and adding anti-friction coatings to various components reduced noise generation. To reduce noise transmission, refrigerant lines were carefully designed and mounted.
Transmission of noise from the cooling module to the body structure had been reduced through the use of a new integrated elastomer isolation and mounting system. Fan shrouds were also stiffer to avoid resonance in the system. Dual fans of different sizes operated at different speeds to avoid beat frequencies.
The following add-on silencing devices and treatments were used on Concorde and Intrepid:
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