Although both TL models share almost identical dimensions and exterior body panels, they are structurally different in many crucial areas. This was largely due to the different vibration characteristics and weight balance of the two engines. As a result, the chassis was developed to optimize the rigidity and crash protection, and to minimize noise, vibration and harshness. In developing the chassis, Acura engineers used the latest Finite Element Analysis and Modeling to achieve the highest rigidity levels at the lightest possible weight. An important tool in achieving these high rigidity targets was the NASA Stress Analysis Program (NASTRAN). This tool allows chassis designers to quickly analyze and evaluate changes in a structure and find the best solution.
Unit Body Structure
The carefully designed structure is designed to help keep the center passenger section protected in the event of an impact. The center "safety cage" is specifically reinforced, and straight frame rails at the front and rear help absorb both direct and offset impact loads.
Radiused Front Frame Rails
The longitudinal engine placement has allowed the creation of a unique front frame rail design. The front frame rails are radiused as they meet the front bulkhead. This design imparts high torsional and bending rigidity to the body, and also maximizes front impact protection by dissipating the loads over a wider area and by directing the load downward toward the floorpan.
Honeycomb Floor Structure
Instead of a conventional steel stamping for the floorpan, the 2.5TL floorpan uses an I8-mm thick honeycomb sandwich. It consists of a resin-impregnated honeycomb material bonded between two layers of zinc-coated steel. This structure imparts considerable strength to the floorpan. In addition to maximizing rigidity, the honeycomb material also serves to block out noise and vibration.
While the structure effectively damps outs annoying vibrations and ensures a tight, rigid body, blocking out road noise is accomplished by using sound deadening material in strategic areas throughout the body. The amount and thickness of this material is different in each model, but a liberal amount of insulating material has been used in the front bulkhead, the floorpan, the rear bulkhead, the rear parcel shelf and the trunk to ensure a quieter passenger cabin. Sound deadening foam material is used in the C-pillars, which in testing has reduced noise in the passenger compartment by 3 decibels.
From bare metal body to the final inspection stage, the TL undergoes a careful 23-step, 3-coat, 3-bake painting process. TL models with pearl white exterior paint undergo a 4-coat, 4-bake process due to the unique requirements of the pearlescent pigment. The process begins by thoroughly cleaning the body of grease and other debris that might mar the final finish or prevent paint from properly bonding to the metal. The body is then put through an electrodeposition coating process, washed and then dried. At that point, the actual process of painting begins. Each successive coat of paint and the clear sealer coat is baked and washed. The final finish is glass-smooth and designed to resist fading for the life of the vehicle.
To ensure excellent corrosion protection, over 90% of the TL outer body panels are made of double-sided galvanized steel. In fact, the only panel that is not galvanized on both sides is the roof. In addition to this, the rocker panels and other selected cavities are filled with an oil-impregnated wax material that inhibits moisture penetration and prevents rust. This, when combined with the excellent painting process, produces a corrosion-resistant body that carries a 5-year rust-through warranty.