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lsquoTree trunkrsquo rear structure blue ties to door ring red to create rigid body
<p><strong>&lsquo;Tree trunk&rsquo; rear structure (<em>blue</em>) ties to door ring (<i>red</i>) to create rigid body.</strong></p>

Acura Engineers Pull Back RDX Skin

Acura engineers built a &ldquo;tree trunk&rdquo; subframe into the rear of the all-new RDX and employed hot-stamped inner and outer door rings to assure chassis rigidity.

DETROIT – A massive, high-strength steel frame member ringing the rear cargo hatch of the all-new ’19 Acura RDX is the first building block engineers employed to improve chassis stiffness and upgrade handling dynamics in the third-generation CUV.

“We call it the ‘tree trunk’ of the structure,” says Joe Riggsby, body development leader, during an under-the-skin engineering review of the RDX here at the SAE World Congress Experience.

“The magic comes from what we were able to do in the rear,” adds Jed Aston, RDX vehicle dynamics leader.

Aston attached an all-new 5-link rear suspension to the rigid structure, replacing the current model’s trailing-arm setup, allowing for significant improvements in handling without sacrificing ride comfort. Shock uppers bolt directly to the ring to tie the entire rear suspension together. The result is a 125% improvement in rear suspension lateral rigidity.

Body engineers settled on the rear-door ring along with a second structural ring to compensate for losses expected when product planners decided to equip every new RDX with a standard panoramic roof. The roof opening, combined with the already large rear cargo door, would have hurt body stiffness if not for the offsetting rigidity of the strong double-ring rear frame members.

Moving forward, the RDX benefits from Acura’s use of an ArcelorMittal-supplied hot-stamped door ring like the structure introduced on the ’14 MDX. The latest iteration, however, is a world’s-first combined inner and outer hot-stamped door ring.

The entire body structure is welded and further tied together with 121 ft. (37 m) of high-performance adhesive that adds stiffness without adding weight. Use of the adhesive saves about 20 lbs. (9 kg). The RDX body-in-white uses 56% high-strength steel and overall is 42 lbs. (19 kg) lighter than its predecessor, while being engineered to meet all crash standards.

To make the RDX sleeker and more proportionally balanced, the body is stretched and widened while the dash-to-front-axle distance increases.

Dual-pinion rack improves steering control.

Steering also gets upgraded to a variable-gear-ratio dual-pinion system in which the steering column is tied directly to the steering rack while a separate electrically driven pinion provides power assistance to the rack. The current RDX is a single-pinion system.

For ’19, the RDX gets a turbocharged 2.0L inline 4-cyl. in place of the current model’s 3.5L V-6, and a 10-speed automatic transmission replaces the older 6-speed automatic. The 2.0L produces 272 hp and 280 lb.-ft. (380 Nm) of torque.

Upgrades in the fourth generation of Super-Handling All-Wheel Drive make the RDX more responsive, able to handle higher torque and more capable of quickly shifting torque to the wheel with traction, says Aaron Alexander, senior engineer-SH-AWD.

[email protected] @bobgritzinger

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