2018 Acura RLX: Chassis

11/13/2017 11:57:00 AM

The 2018 RLX's handling and ride comfort have been further optimized for 2018. Developed to be true "driver's cars," the new RLX P-AWS and RLX Sport Hybrid both deliver improved linearity of yaw response. With a smooth and quiet ride, all-wheel steering on the RLX P-AWS and electric motor-powered torque vectoring on the RLX Sport Hybrid, the 2018 RLX lineup offers technology and performance unmatched by other vehicles in the competitive luxury segment.

Powerful Technology
Proven technologies that help define the RLX P-AWS and RLX Sport Hybrid as comfortable, confident and capable luxury sport sedans continue for 2018, including high-output belt-type Electric Power Steering (EPS), double-wishbone front and multi-link rear suspension, front and rear Amplitude Reactive Dampers, and a selectable Sport mode. Together, these advanced technologies allow the updated RLX and RLX Sport Hybrid to master driving conditions as disparate as city traffic and freeways, winding roads and wide-open rural Interstates, inclement weather conditions, and sudden emergency situations. Accurate, confident and fun-to-drive, the 2018 RLX P-AWS and RLX Sport Hybrid represent the finest interpretation yet of Acura's flagship sedan.

Key traits of the RLX chassis dynamics include:

  • Agile and accurate cornering with linear response
  • Smooth, connected and naturally fluid handling
  • Outstanding high-speed stability
  • Comfortable, flat and smooth ride
  • Confident braking performance
  • Outstanding steering feel
  • Low NVH properties

Summary of Chassis Technology

RLX P-AWS

  • Precision All-Wheel Steer™ (P-AWS®) and Agile Handling Assist
  • Sport Mode
  • Front Aluminum Subframe
  • Double-Wishbone, Lower Double-Joint Front Suspension 
  • Multi-Link Rear Suspension
  • Amplitude Reactive Dampers
  • High-Output Electric Power Steering (EPS)
  • Rigid Steering Column
  • 4-Wheel Disc Brakes
  • Electric Parking Brake + Automatic Brake Hold
  • Vehicle Stability Assist™ (VSA®)
  • Tire Pressure Monitoring System (TPMS)
  • Noise-Reducing Aluminum Alloy Wheels
  • 245/40 R19 All-Season Tires
  • 19 x 8.0 inch aluminum alloy wheels
  • 18.5-gallon Fuel Capacity
  • Capless Fueling System

RLX Sport Hybrid (in addition or instead of)

  • Sport Hybrid Super Handling All-Wheel Drive (SH-AWD)
  • Electric Servo Brakes
  • 15.1-gallon fuel capacity

Precision All-Wheel Steer™ (FWD RLX only) and Agile Handling Assist
Precision All-Wheel Steer™ (P-AWS®) and Agile Handling Assist are standard on the front-wheel-drive RLX. This combination of technologies helps the RLX driver smoothly and easily trace the desired line with minimal steering-wheel inputs. The result is extremely linear dynamic performance in all driving conditions, which directly helps RLX perform at the will of the driver.

Precision All-Wheel Steer® (P-AWS®)
Standard on the front-wheel-drive 2018 RLX, Precision All-Wheel Steer™ (P-AWS®) is an all-electric left/right independent rear-wheel toe angle control system. Benefits of the system include:

  • Minimized turning radius with neater execution of sharp low-speed turns
  • Improved response for quick steering maneuvers such as lane changes
  • Enhanced agility and nimbleness at roundabouts and intersections
  • More confidence and control on curved highway on- and off-ramps
  • Greater agility on winding roads
  • Increased straight-line highway stability
  • Confident braking stability
  • Improved high speed response and stability in winter driving and when Vehicle Stability Assist™ (VSA®) is activated

System Operation
Key components of P-AWS® include independent electrically assisted left/right actuators, special control arms and suspension uprights, and an electronic control unit that is linked via a dedicated Control Area Network (CAN) to the Electric Power Steering (EPS), Vehicle Stability Assist® (VSA™), braking and engine control systems.

In operation, P-AWS® continuously monitors and calculates the correct amount of rear-toe angle input necessary for conditions, analyzing steering input, engine and road speed, transmission, throttle position, brake pressure, yaw rate, lateral acceleration and other factors. The maximum amount of rear-wheel toe angle adjustment is 2.0 degrees in either direction (positive or negative) for a total range of 4.0 degrees.

There are four fully automatic levels of P-AWS system operation to match such driving situations such as turning at an intersection, driving on windy roads, when merging or exiting a highway, higher speed maneuvers or in snowy conditions. The P-AWS® system provides confidence-building cornering capability through improved responsiveness and vehicle control.

Examples include:

  • When the driver initiates a lane-change maneuver requiring that the RLX neatly move into the next lane, the P-AWS® system adjusts the rear wheel toe angles in phase (the same direction) with the front wheels enabling quick, clean maneuvering.
  • For sharp low-speed turns, such as on city streets or in parking lots, the P-AWS® system adjusts the rear wheels toe angles out of phase (the opposite direction) with the front wheels. This results in a tighter turning radius.
  • When tracing the lines of a twisty road – and helping the RLX track confidently in snowy conditions – the P-AWS® system counteracts understeer by helping introduce yaw – the necessary rotational effect – through the corner.

P- AWS® Modes
P-AWS® can provide rear-wheel toe-in, in-phase steering or out-of-phase steering, depending on the dynamic requirements as dictated by the system ECU specific key rear-wheel toe angle adjustments include:

Driving Situation

Rear Wheel Steering Action

Effect

Braking

Toe in (both wheels, simultaneously)

Increased stability

Tight cornering

Reverse phase

Increased agility (induces yaw rate),

Acceleration exiting a corner

Toe control to reduce understeer

Increased traceability

Lane change

In phase

Increased agility and stability (reduces yaw rate)

Parking

Reverse phase

Reduces turning radius

Sport Mode
A driver-selectable Sport mode further enhances driving dynamics across a wide range of driving situations. These include:

  • Revised drivetrain-related mapping for increased acceleration
  • To match the improved acceleration, steering and braking systems were tuned to:
    • Avoid larger than intended steering inputs via reduced steering assist
    • Further increase brake effectiveness (RLX Sport Hybrid)

Front Aluminum Subframe
The RLX's front aluminum subframe is specifically designed to support the high performance of the double-wishbone front suspension and Electric Power Steering (EPS) systems. Using die-cast front corners, the subframe is especially lightweight and rigid. This directly contributes to the vehicle's agile and light handling, straight-line stability, high fuel efficiency, flat cornering and pleasing ride comfort, and smooth and precise steering feel (with minimal torque steer tendencies).

The RLX subframe is matched to the Active Control Engine Mount (ACM) system that is engineered specifically for the RLX's higher-output engine and Variable Cylinder Management (VCM) system.

Double Wishbone, Lower Double-Joint Front Suspension
The RLX's double-wishbone, lower double-joint front suspension provides highly intuitive handling agility, driver confidence and security, and ride sophistication. The system includes a lower double joint with a split lower control arm, optimized kingpin geometry, upper control arm, hydraulic compliance bushing, special dual-stage Amplitude Reactive Dampers, and a stabilizer bar that is heat treated for high strength.

Two front stabilizer bar specifications are used: the front-wheel drive RLX has a 32 mm diameter tubular steel front stabilizer bar with a tubing wall thickness of 3.9 mm. The RLX Sport Hybrid also uses a 32 mm diameter tubular front stabilizer bar, but with a thinner 3.5 mm tubing wall thickness that results in reduced stabilizer bar stiffness.

All RLX models use a 24.6 mm diameter rear stabilizer bar with 3.6 mm tubing wall thickness, hardened with a special shot-peening process.

Multi-Link Rear Suspension
Like the double-wishbone, lower double-joint front suspension, the RLX's multi-link rear suspension with Amplitude Reactive Dampers provides optimal handling agility, driver confidence and ride sophistication. The multi-link system geometry is optimized for a flat ride during cornering, confident turning capability, and a sophisticated ride in a variety of urban, highway and open road scenarios. The system includes multi-link control arms, control-arm bushings that are optimized for the best blend of NVH isolation and handling precision, Amplitude Reactive Dampers, and a rear stabilizer bar.

Amplitude Reactive Dampers
Amplitude Reactive Dampers provide superior ride comfort and handling in all driving conditions. The dampers have two separate damping mechanisms: one that is tuned for maximum efficiency on smoother roads with small, higher-frequency inputs; and the other that is tuned to handle larger, low-speed damper inputs such as rough roads, potholes, and sudden steering and braking action. The result is a vehicle that remains composed and comfortable in a wide range of driving conditions.

The Amplitude Reactive Dampers are a purely mechanical system that does not require electronic controls. Their core technology is two separate damping pistons, including a main piston and a second piston. To improve overall ride comfort, when smaller inputs occur during normal driving conditions, only the main piston works to provide the ideal damping characteristics. To improve the RLX's ride and handling during more severe conditions, the second piston operates to provide additional damping force.

High-Output Electric Power Steering (EPS)
The RLX's Electric Power Steering (EPS) system uses a high-output electric motor with a belt-drive system to increase the torque available and assist the driver in steering the vehicle. The result is smooth and instantaneous response, direct feel, and improved low-speed agility and high-speed stability.

The variable gear ratio system is designed and tuned to provide the two most essential characteristics in a high-performance luxury vehicle's steering. These include a smooth initial response (short delay) at the start of steering input, and great linearity response (steering force camber increase) as input is increased. As a result, the RLX's high-output EPS provides agile performance in low-speed driving maneuvers such as at intersections, improved overall accuracy and road feel, and superb high-speed stability.

Rigid Steering Column
The RLX steering column is a highly rigid design with an aluminum bracket and resin angular bearing. The resulting stiffness gives maximum driver steering feedback along with minimizing vibration felt in the wheel.

The large-diameter steering shaft and the stiff but lightweight aluminum support bracket and angular bearing yield maximum vibration-damping characteristics for a more luxurious driving experience.

Electrically actuated tilt and telescoping adjustment makes it easy to set the steering wheel to the ideal position for drivers of different sizes.

4-Wheel Disc Brakes with ABS and Brake Assist
Both 2018 RLX models are equipped with 4-wheel disc brakes with a 4-channel anti-lock braking system (ABS) for confident stops. The front discs on the RLX P-AWS measure 12.3 inches in diameter, while the front discs on the RLX Sport Hybrid measure 13.0 inches in diameter. Both RLX models feature 12.2-inch rear disc brakes.

ABS independently modulates braking power at each wheel to help the driver retain steering control during heavy braking, while Brake Assist recognizes emergency braking situations and almost instantly applies full braking force when appropriate.

The brake pads are a high-friction type for peak stopping performance even under strenuous conditions. The brake calipers are designed to reduce brake drag when not in use, reducing rolling resistance and improving fuel efficiency in the process.

The Hydraulic Brake Boost (HBB) improves brake pedal feel by utilizing a hydraulic boost system with a 10-in. high-pressure master cylinder. The system automatically and continuously analyzes and interprets the driver's brake-pedal inputs and adjusts the braking force to suit.

Electric Servo Brakes
The RLX Sport Hybrid's electric servo brake system maximizes regenerative braking capability for improved fuel efficiency. The mechanical braking system is hydraulic from the master cylinder to the 4-wheel disc brakes, just like a traditional braking system. The key difference is that the braking function is electronically controlled rather than a purely mechanical activation.  This allows for the application of regenerative braking by the front and rear electric motors to slow the vehicle, rather than the hydraulic friction brakes, under most circumstances, with the additional of mechanical (friction) braking in hard stops. Besides its payoff in efficiency, the system offers excellent feel and feedback for the driver through the brake pedal.

When the driver applies the brake pedal, a signal is sent to the vehicle's Electronic Control Unit (ECU), which determines the appropriate amount of braking force to assign to regenerative braking through the electric drive motor and to the hydraulic friction braking system. In many cases, friction braking is not needed until the vehicle speed drops below 9 mph, as the vehicle slows to a final stop. When the ECU determines that friction braking is needed, the dual hydraulic master cylinder pumps brake fluid through the system. Midway between the master cylinder and the calipers is a separate motorized electronic actuator. This actuator receives an electronic signal, generated in the master cylinder module that precisely defines how the driver has applied the brakes – soft or hard, slow or fast. The actuator then directly apportions hydraulic pressure to the brake calipers at each wheel.

While the front-wheel-drive RLX uses a 10-inch vacuum booster to assist the driver in applying needed brake pressure, the all-wheel-drive RLX Sport Hybrid with regenerative braking uses an electric servo brake actuator.

Reactive Force Pedal
The RLX Sport Hybrid includes Reactive Force Pedal technology. In Normal mode, the system measures vehicle speed and dynamically varies pedal force to help the driver in applying the optimal amount of throttle for both spirited performance and good fuel economy. In slippery conditions, the system can also help the driver apply the optimal amount of driving force while minimizing wheel slip, utilizing input from the Vehicle Stability Assist™ (VSA®) system. In the event that the Collision Mitigation Brake System™ (CMBS™) detects that a frontal collision is imminent, the Reactive Force Pedal will push back on the driver's foot even before the CMBS system activates its visual and auditory alerts.

Electric Parking Brake + Automatic Brake Hold
The combination of Electric Parking Brake (EPB) and Automatic Brake Hold significantly reduce the effort of driving the vehicle, raising overall comfort and convenience.

Electric Parking Brake
The Electric Parking Brake (EPB) makes using the parking brake easier and more comfortable. Actuating the parking brake is as simple as pulling a button on the center console. To release the parking brake, the driver simply presses on the accelerator pedal. In addition to being simpler, more convenient and more comfortable to use than a traditional parking brake, the Electric Parking Brake makes hill starts easier when the RLX is parked on a grade.

The ease of use also promotes the use of the parking brake. As with a traditional manually activated parking brake, EPB functions on the rear wheels only.

Automatic Brake Hold
Automatic Brake Hold retains brake pressure when the vehicle is stopped, simplifying driving in heavy traffic or hills. This frees the driver from continually pressing the brake pedal to maintain the vehicle in a stopped position, a significant improvement in driving enjoyment in difficult conditions.

Operating the system requires two simple actions from the driver:

  • Activating/deactivating the system via a switch on the center console.
  • Pressing on the brake pedal when the vehicle comes to a stop.

Once these steps are taken, Automatic Brake Hold will indicate engagement and then maintain brake pressure when the vehicle has come to a stop, even if the driver releases the brake pedal. The RLX then remains stopped – even on a hill – until the driver presses the accelerator pedal. At this point, Automatic Brake Hold releases the brakes and the vehicle resumes normal braking function.

Vehicle Stability Assist™ (VSA®)
The RLX's high-efficiency Vehicle Stability Assist™ (VSA®) works in conjunction with the ABS and the Drive-by-Wire throttle systems. The VSA system enhances vehicle stability when cornering. If vehicle understeer or oversteer is detected, the system selectively reduces power and/or applies braking force to individual wheels to help correct the condition and stabilize the vehicle.

Traction control monitors front-wheel slippage, such as when starting on slick surfaces or patches of ice. If it is detected, traction control activates one or more brake calipers and reduces engine torque to slow the spinning wheel so it can regain traction.

Tire Pressure Monitoring System (TPMS)
A standard direct type Tire Pressure Monitoring System (TPMS) helps the driver maintain proper air pressure to improve driving safety and fuel efficiency, as well as reduce wear and tear on the vehicle's tires. Located in the instrument panel, a TPMS icon illuminates to alert the driver whenever any of the tires has a significantly low-pressure reading that requires the driver's attention. The current pressure for each tire in PSI can also be displayed.

Noise-Reducing Wheels
Both RLX models feature 19x8-inch aluminum alloy wheels as standard equipment.
The RLX P-AWS wheels are painted Pewter gray and machined finished. The RLX Sport Hybrid wheels feature a sporty shark gray color and machined finish.

All RLX wheels have a special noise-reducing design that lowers noise by 6 dB across the audible frequency range (200 to 230 Hertz). The key elements of the noise-reducing function are a resonator and a resin molding that are applied in a band on the inside of the rim. The result is reduced noise resonance in the air column inside the wheel. One important benefit of the noise-reducing wheel technology is a noticeable reduction in audible thumping or bumping noises when the RLX crosses expansion joints on the roadway.

All-Season Tires
Michelin Primacy MXM4 245/40R19 high-performance all-season tires are standard equipment on both RLX models. To maximize trunk volume, the both models also feature an easy-to-use tire repair kit (TRK).

18.5-Gallon Fuel Capacity
The RLX's 18.5-gallon fuel-tank capacity (15.1 gallons on the RLX Sport Hybrid) gives an ample cruising range. Both the fuel tank and fuel pipe are molded of high-density polyethylene for low weight, freedom from corrosion, impact resistance and fuel vapor losses. The fuel tank is located in a protected area in front of the rear suspension to help improve safety performance in the event of a collision.

Chassis Features

 

2018 RLX P-AWS

2018 RLX Sport Hybrid

Double-Wishbone, Lower Double-Joint Fr. Suspension 

Multi-Link Rear Suspension

Stabilizer Bar, Front/Rear (mm)

32/24.6

32/24.6

Amplitude Reactive Dampers

Belt-type Electric Power Steering (EPS)

Steering Wheel Turns, Lock-to-Lock

2.6

2.6

Steering Ratio

13.9:1

13.9:1

Turning Diameter, Curb-to-Curb (ft.)

40.5

40.5

Ventilated Front Disc/Rear Solid Disc Brakes (in.)

12.3/12.2

13.0/12.2

Wheels (front and rear)

19x8J, aluminum alloy

19x8J, aluminum alloy

High-Performance All-Season Tires

245/40R19 98W

245/40R19 98W

Spare Tire

Tire Repair Kit

Tire Repair Kit