OVERVIEW
The 3.5 RL is equipped with 4-wheel, independent
double-wishbone
suspension with coil springs, 4-wheel disc brakes with
ventilated
front rotors, Anti-lock Braking System (ABS), and stabilizer bars
at
both front and rear.
LOW-FRICTION DOUBLE-WISHBONE SUSPENSION
The RL's double-wishbone suspension layout is tuned to
optimize
handling quickness and stability without sacrificing ride quality.
Optimized spring and damping rates, large front and rear
stabilizer
bars and firm front suspension bushings gives the car a sporty
feel.
The front suspension uses unequal-length upper and lower
control arms
and a tubular stabilizer bar, while the rear suspension combines
a
longitudinal trailing arm, three lateral links and a tubular
stabilizer. For excellent stability and improved ride quality,
anti-squat and anti-dive geometries were built into the RL
suspension.
To achieve a compliant ride without compromising handling response or cornering capability, the RL suspension also uses a number of innovations to reduce friction throughout suspension travel. The stabilizer bars use highly efficient ball joints at either end, as well as self-lubricating bushings at the sub-frame mounts. The upper arms of both the front and rear suspension have low-friction ball-joint bushings where they attach to the main structure, reducing overall friction while enhancing rigidity of the suspension assembly. Dampers have an advanced Progressive Valve design for increased damping control at low damper speeds while retaining quick, fluid response to large impacts. Special Teflon seals within all four damper units reduce friction even further for improved ride quality.
LOW ROLL CENTER
To give the RL a stable, predictable feel during hard cornering
while
improving overall lateral-acceleration capability, the suspension
geometry was designed with a low roll center. The roll center is
59
mm above ground level for the front suspension and 70 mm
above ground
level for the rear suspension.
LIQUID-FILLED REAR TRAILING ARM BUSHING
To reduce road noise and harshness, the bushing at the front of
the
rear-trailing arms is a liquid-filled design, instead of the more
conventional rubber-damped bushing.
VEHICLE STABILITY ASSIST (VSA) SYSTEM
The standard, state-of-the-art Vehicle Stability Assist (VSA)
system
provides a heightened sense of stability in all driving conditions.
Developed in cooperation with Bosch, this 4-channel system
orchestrates the throttle and each of the RL's four disc brakes
independently to seamlessly integrate traction control, Anti-lock
braking, and stability enhancement processes under widely
divergent
road and driving conditions.
By monitoring input from vehicle sensors, the VSA can calculate a predicted range of vehicle response while constantly monitoring the vehicle's actual response and the driver's control inputs. If the actual response is outside of the predicted response range - as when cornering forces exceed tire performance, for example - VSA automatically takes corrective action. In the case of oversteer during hard cornering, VSA applies braking to the outside front or rear wheel to help counter the unintended yawing tendency. If understeer occurs, VSA applies braking to the inside front or rear wheel to help turn the RL back onto the intended course.
Unlike some vehicle stability systems, which can seem intrusive to enthusiast drivers, the Acura VSA is calibrated to add stability and predictability without stifling the driving enjoyment of the RL's carefully engineered chassis and double wishbone suspension. An indicator light flashes on the instrument panel while the system is actively stabilizing the vehicle. A cockpit switch is provided to disable the vehicle stability and traction control aspects of the system while leaving the ABS system fully functional.
TRACTION CONTROL
The traction control aspect of the VSA system works just as
seamlessly. When wheel slip is detected under acceleration,
differential braking and engine controls modulate the amount of
power
put to the ground. In situations where the drive wheels are on
surfaces with different friction properties, such as when one
drive
wheel is on wet pavement while the other is on dry pavement,
the
system applies pulsed braking action to the wheel that is
slipping,
allowing the tire with better grip to move the vehicle. In addition
to taking independent control of the front wheel brake, the
system
can also reduce total engine power output to keep wheel spin in
check.
BRAKING SYSTEM
Large, power-assisted, 4-wheel disc brakes are standard, with
ventilated rotors in front for minimal fade and excellent heat
dissipation. By fine-tuning the leverage ratio of the brake pedal
and
the response characteristics of the power-brake vacuum
diaphragm, the
RL engineering team achieved reduced stopping distances
while making
brake response more linear and intuitive. Combined with the
"low-creep" torque converter, these refinements also help make
it
easier to hold the RL at a stop.
ANTI-LOCK BRAKING SYSTEM (ABS)
The 3.5 RL has a 4-wheel, 4-channel Anti-lock Braking System
(ABS)
that works independently of and in concert with the VSA system
as
needed. The ABS system operates in 3-channel mode during
straight-line braking (apportioning braking power to the front
wheels
independently and the rear wheels in tandem), but automatically
switches to 4-channel mode when the VSA system senses high
cornering
forces. This allows the ABS system to take advantage of weight
transfer to the outside of the turn during cornering and apply
higher
brake pressure to the outer rear wheel for enhanced braking
performance.
The ABS enhances steering control during hard braking. Speed sensors at each wheel send signals to the ABS control module; if the system detects impending wheel lockup, it first holds, then reduces hydraulic pressure to the affected wheel, letting it regain traction before full braking resumes. The ABS function is also highly effective on split-friction surfaces, in which one side of the vehicle has significantly less traction than the other.
ROTARY-VALVE, VARIABLE POWER-ASSISTED,
RACK-AND-PINION POWER
STEERING
The speed-sensitive, variable power-assisted, rack-and-pinion
steering uses a rotary valve that senses torque applied to the
steering wheel and a vehicle speed sensor to vary power assist
accordingly. The system adjusts steering assist for easy
steering at
low speeds and quick, precise steering at high speeds. The RL
utilizes a cast-magnesium steering wheel for lighter steering
feel,
and a dynamic damper in the steering shaft for reduced wheel
vibration.
WHEELS AND TIRES
The 2003 Acura 3.5 RL is equipped with wide P225/55R16
Michelin tires
on aluminum alloy wheels. The wide tires help provide
outstanding
all-season grip and performance, while maintaining exceptional
ride
characteristics and helping achieve optimal fuel mileage. The
tires
are an all-season design for enhanced traction on wet roads as
well
as on dry pavement.