2001 Acura 3.5 RL -- Structure & Body

The 3.5 RL has a stamped-sheet-steel unit-body structure, designed to have a very high level of overall rigidity in both bending and torsion. The highly rigid structure was developed using a Cray supercomputer running the NASTRAN finite element-analysis program originally developed by NASA for building space vehicles. The chassis was made even more rigid by a rear support gusset, a large bulkhead bracket and rear crossbeam stabilizer.

The high rigidity of the 3.5 RL unit-body structure reduces noise and vibration in the passenger cabin, enhances handling precision and stability, creates excellent safety performance and increases overall durability. A high proportion of galvanized panels are used in the 3.5 RL structure and body panels for enhanced corrosion protection and overall longevity.

Instead of a conventional tubular steel front brace between the firewall and the upper front-suspension locating points, the RL uses an oversized, oval-section tower bar brace, as well as a reinforcing plate that ties the firewall and front cowl section. This design increases rigidity as much as 12 times over a conventional round tube design, reducing cowl shake on rough roads and in spirited driving, while increasing steering precision.

For reduced cabin-noise transmission, the B- and C-pillars are filled with a special heat-expanding rubberized foam material that expands to fill the hollow pillar during the baking cycles of the painting process.

Special lightweight honeycomb panels are used in the floor structure to increase rigidity and reduce noise and vibration. These panels are composed of a resin-impregnated fiber matrix bonded top and bottom to thin-gauge galvanized steel sheets.


The 3.5 RL body design is intended to impart a muscular stance and dynamic appearance while maintaining an enduring elegance and sophistication. The body of the 3.5 RL is significantly taller than previous Acura luxury sedans, for improved headroom, especially in the rear seats, and a more substantial exterior appearance. The 3.5 RL flanks are designed with high, relatively prominent "shoulder" lines, for a strong, masculine appearance, and the front grille/fender/bumper area is designed with a very clean, integrated configuration, giving a more massive, yet aerodynamically efficient look.

The 3.5 RL has a low coefficient of drag of 0.32 and a coefficient of lift of 0.102, resulting in greater high-speed stability and a very quiet, distraction-free interior environment.

The RL is engineered and painstakingly assembled to have a level of fit and finish second to none in the luxury sedan class. Panels have been combined and integrated, wherever possible, to eliminate gaps and seams.

The tall, spacious-feeling greenhouse of the RL is designed to give the driver and passengers a clear, panoramic view of the road ahead and the surroundings to the sides and rear for enhanced safety. The driver's front, side and rear views are largely unobstructed, due to slim, yet highly rigid, roof pillars. The body is designed to give the driver a clear sense of the boundaries of the car, for more secure maneuvering and parking.

The RL is built with a high proportion of galvanized steel panels, most of them galvanized on both sides for superior corrosion protection. All visible surfaces are protected by a 23-step, 4-coat, 4-bake paint process, with special antichip primer and special chip-resistant paint used in areas that are likely to be struck by stones or other debris. The paint process is so precise and exacting that personnel who work in the painting section of the factory wear special contamination-free clothing while working and are checked for colognes or other cosmetic chemicals that might cause the slightest contamination of the painting environment. Chassis panels are protected by corrosion-resistant undercoating material, and body cavities are injected with an oil-based anticorrosion wax that displaces moisture for even better protection.

The ultra-high quality appearance of the RL is enhanced by a special crystal structure cast into the inner surface of the RL rear outer-lens assembly.

As an example of the extraordinary lengths taken to reduce wind noise, the outside rearview mirrors are designed with a small wind deflector, or spoiler, that directs oncoming air down and away from the mirror assembly. By detaching the airflow under the mirror, the deflector reduces the pressure gradient between the air rushing around the mirror housing and the still air behind the mirror, eliminating a "whistling" effect there that has been identified as a cause of wind noise in the wind tunnel.

The RL includes an innovative power moon roof. The outer moon roof panel first tilts up, for increased ventilation, and then opens completely with one additional touch of the control button. Heat-rejecting privacy glass is used, and the moon roof is programmed to pause at the 130 mm position during closing to help ensure passenger safety.

A special spoiler, located immediately behind the front bumper, has been developed to reduce airflow under the RL, thereby reducing the high-pressure air under the front of the body and diverting it to flow around the sides and over the top. This reduces drag and front-end lift and also reduces wind noise, helping to give the RL a remarkably quiet interior, even at high speeds.

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