The new Acura TSX is more than Acura's entry sedan.
It is a responsive, balanced, sharp-handling sports sedan that is designed to
compete on equal terms with Europe's best -whether front-drive, rear-drive or
all-wheel drive. This capability begins with impressive unit body stiffness,
which allows the precise tuning of the double-wishbone front and rear suspension
systems for maximum responsiveness, flat cornering, and high-speed stability.
GOALS AND BENCHMARKS
The ride, handling and stability targets for the new
Acura TSX were to be better than the most respected compact sport sedans of
Europe. As explained in the previous body section, this high performance level
required an especially stiff unit body structure to enhance ride and handling
precision as well as crash safety. This robust structure makes it possible to
tune the suspension for a responsive, satisfying sport driving experience-not to
compensate for body flex and resonance.
In today's sophisticated sport sedan market, one of the greatest challenges
is in finding a balance that offers sports-car like handling, reassuring
high-speed stability and abundant comfort for passengers at all times. To
accomplish this, Acura chose independent double-wishbone front and rear
suspension with a combination of steel and aluminum components and specific
geometry designed to control lift, dive and body roll. The result is exceptional
dynamic performance and stability at all speeds, a very comfortable ride, and
greater confidence and enjoyment for the driver and passengers. Even as it
approaches its high ultimate cornering limits, the TSX responds accurately to
steering and throttle inputs.
FRONT SUSPENSION
The TSX front suspension is a double-wishbone system with
sport-tuned shock absorbers and stabilizer, and a shock-tower bar. This set up
provides quick response and precise suspension geometry control throughout its
range of travel. This is evident when the TSX is driven hard through uneven or
undulating corners. The car remains balanced and composed in an environment
where even some premium European products become unsettled.
Computer-developed front suspension geometry allowed TSX designers to build
in subtle handling enhancements. The TSX has pronounced steering self-centering
to improve high-speed stability and lane control. There is also an anti-dive
aspect to the geometry to keep the TSX from pitching forward excessively during
hard braking, so the car feels more composed. Anti-lift aspects minimizes
excessive front end lift during hard acceleration. Subtle changes to front wheel
toe control while cornering and braking simultaneously further improve vehicle
stability. A special compliance bushing located at the front of the front
suspension subframe allows controlled fore-aft compliance under rough road
conditions, netting superior ride quality.
Both front and rear suspension systems use coil-over shock absorbers that
offer quick response and particularly high rebound damping rates, coupled with
relatively firm springs. As the stiffer springs compress, this stronger rebound
damping is required to control the spring energy as it is released. Extensive
on-road and racetrack testing in Europe, America and Japan was used to find the
ideal suspension tuning balance between sporting performance and ride comfort.
REAR SUSPENSION
In keeping with the goals of sporty handling for TSX, a
5-link rear suspension design is employed. The system utilizes an aluminum
knuckle and double tubular wishbones. The light aluminum knuckle yields a weight
reduction of 13.2 lbs. while providing 50 percent greater rigidity over iron.
One benefit of the lighter knuckle is better ride quality. Because it has less
"unsprung" weight, the suspension is more responsive to road roughness.
Like the front suspension, the system uses anti-dive geometry that helps keep
the TSX stable-and the passengers more comfortable-during hard braking. Built-in
toe control geometry helps optimize vehicle stability during corner turn-in,
while a high level of roll stiffness, provided by a stabilizer bar, also helps
the TSX remain stable during hard cornering by minimizing body roll.
Acura engineers adjusted the rear suspension "roll center" (the theoretical
axis around which the car "rolls" or leans while cornering) to be as close as
practical to its center of gravity (the height at which the vehicle's weight is
effectively centered). This enhances the responsiveness and helps the TSX body
to remain flat during sharp maneuvering.
POWER RACK-AND-PINION STEERING
There were three primary goals in
developing the quick-ratio power rack-and-pinion steering system: reduce
resistance in the system, improve linearity of steering response, and reduce
steering-wheel kickback on rough roads. Here's how these objectives were
accomplished.
- A lighter feel was obtained by tightening the tolerances in the
rack-and-pinion assembly and adopting a steering damper with a variable-damping
feature.
- Improving the stiffness of the steering mounting bushing and subframe
yielded a more linear steering response on-center by reducing variance in the
mounting assembly.
- To reduce kickback, a special variable hydraulic valve was incorporated into
the steering gearbox valve housing. The valve works to absorb sudden shock in
the steering system such as caused by potholes. It markedly reduces the kickback
torque to the steering wheel in such instances.
P215/50R17 TIRES
The standard P215/50R17 93V MXM4 M+S all-season
high-performance tires on the TSX provide an impressive combination of ride and
handling. Jointly developed by Acura and Michelin, these tires also promote fuel
efficiency through reduced rolling resistance. The tires mount on 17x7-inch
aluminum wheels to visually fill the wheel arches, giving the TSX a more
aggressive, muscular appearance.
BRAKING
The TSX has 4-wheel disc brakes with large 11.8-inch ventilated
front rotors and 10.2-inch solid rear rotors designed to provide exceptional
braking feel. A 4-channel anti-lock braking system is standard.
To achieve a solid brake pedal feel, engineers used three main strategies:
- A low 2.6:1 pedal ratio is used, together with a small 20.6 mm master
cylinder piston. This reduces pedal travel and provides better brake "feel."
- A lighter and more powerful single (instead of tandem) master power vacuum
unit improves stopping power.
- Ultra-stiff front brake calipers that reduce flex and require 8-percent less
pedal stroke.
These components provide the TSX with a state-of-the-art braking system that
delivers in a firm, confidence inspiring pedal feel with excellent braking
effect, even in severe conditions.
VEHICLE STABILITY ASSIST
Vehicle Stability Assist (VSA) is standard on
every Acura TSX. It uses anti-lock braking system (ABS) technology, together
with lateral acceleration sensors, wheel-speed sensors, steering position
sensors and a dedicated microprocessor to detect wheel slip (understeer or
oversteer). This helps the driver control the vehicle through a nearly
instantaneous reduction in engine output (through the drive-by-wire throttle
control) or the rapid pulsing application of one or more brakes as appropriate.
For example, if the driver enters a corner too quickly and the vehicle's
front wheels begin to slip (understeer), VSA almost instantly detects the
situation and interprets it as understeer. VSA then reduces engine torque and
selectively applies the brake on the inner front and rear wheels to help counter
the understeer and enhance the driver's control. The correction happens so
quickly and so seamlessly that the situation is often resolved before the driver
is even aware of it.
Another potential scenario involves a traction loss at the rear wheels, such
as might be encountered when cornering on a dirty road or when encountering
black ice. VSA detects the rear tires beginning to slip and quickly applies the
outer front and rear brakes to counter the unwanted yawing motion and help
restore control to the driver.
VSA is armed automatically when the TSX starts. Any time the system is
triggered, an instrument-panel-warning lamp alerts the driver that VSA is
operating. The system can be switched off completely via an
instrument-panel-mounted switch.
The VSA system also handles traction control functions, enabling the vehicle
to start and climb hills on low-friction surfaces with much greater ability and
controllability. It utilizes ABS technology to sense wheel spin on the front
(drive) wheels, then implements individual brake application and drive-by-wire
throttle control to restore traction. The benefit is greater security and active
safety during winter snow driving or on other slippery surfaces including sand
or water.
Courtesy of acuranews.com
Copyright © by All-Acura All Right Reserved.
