OVERVIEW
The new CL has been engineered from the ground up to provide
extraordinary performance that rivals Europe's finest mid-luxury
coupes. The engineering goals for the second-generation CL chassis
have been achieved by enhancing sporty performance while preserving
luxury feel. These seemingly contradictory requirements are embodied
by the Global Mid-Size Platform. This new-generation front-drive
platform combines the packaging efficiency and performance of a
transversely mounted front-drive powertrain with Acura's latest
thinking on suspension and chassis architecture.
Similar to the chassis architecture of the 3.2 TL performance luxury sedan, the new generation CL further enhances the pursuit of advanced performance dynamics coupled with grand touring refinement. The CL chassis rewards the enthusiast driver with more neutral handling characteristics by employing isolated front and rear subframes and carries its engine on vacuum-controlled front and rear hydraulic mounts. The double-wishbone suspension has geometric refinements that significantly improve the CL's response to steering input. An upgraded ABS disc brake system with larger front and rear discs and more rigid front and rear calipers has been added along with enhanced cornering grip through standard 16-inch wheels on the 3.2 CL and 17-inch on the Type S.
The Type S suspension has been further tuned beyond the 3.2 CL's already impressive capabilities to offer an even greater level of performance handling through larger diameter rear stabilizer bars, stiffer front and rear springs, more compression and rebound damping, along with longer front bump stops.
These chassis elements of the new CL combine to create a high performance coupe that steers, corners, brakes and drives more aggressively and predictably than the car it replaces.
The following are the key areas of advancement to the new CL chassis:
Ride and handling
- Refined double-wishbone front suspension
- New multi-link double-wishbone rear suspension
- Tire and wheel diameter is 16 inches for the 3.2 CL and 17 inches on Type S
- Steering enhancements improve linearity of steering feel
- Isolated front and rear subframes
- Vacuum-controlled hydraulic front and rear engine mounts
Braking
- Enlarged front and rear discs along with a drum-in-disc rear design allow separation of service and parking brake systems for improved effectiveness in high deceleration stops
Steering
- Power steering with improved feel
- Rubber coupling in steering column improves shock isolation and maintains linearity to maintain steering feedback
Safety
- Standard Anti-lock Braking System (ABS)
- Standard Traction Control System (TCS)
- Vehicle Stability Assist (VSA) System -- Type S only
FRONT SUSPENSION
All Acura vehicles employ double-wishbone suspension for the precise
control of wheel motion it allows. For the new generation CL, Acura
engineers redesigned the layout of the front suspension to take
advantage of the stiffness of the new front subframe. The
repositioned suspension arms deliver altered suspension geometry
contributing to the car's responsive handling. A strut tower bar also
helps maintain precise suspension geometry positioning during
cornering. Relative to the previous generation CL, the new coupe
rides on firmer coil springs and dampers and larger stabilizer bars
to provide a more confident driving feel and improved handling
characteristics.
Additional tuning to the Type S front suspension above and beyond the 3.2 CL include stiffer springs increased compression and rebound damping, along with longer bump stops to help fine tune the suspension for more sporty handling. These suspension enhancements allow the Type S to corner confidently and maintain an optimum body stance for maximum performance.
REAR SUSPENSION
The CL's rear suspension has been completely redesigned to provide
sporty handling and a smooth ride without intruding on interior or
trunk space.
The compact high-tension steel suspension links reduce weight and carry the rear wheels through a wheel path that's angled rearward to improve bump compliance and limit bump steer. This geometry also provides a much straighter toe-in curve, meaning that during suspension motion, there is controlled "rear wheel steer" taking place. Pillow joints are also applied to better control side-force steer while reducing component friction to improve ride comfort. As in the front suspension, rear spring rates have been increased, a larger stabilizer bar added and dampers recalibrated to improve the CL's handling during hard cornering.
The Type S rear suspension, like the front, benefits from stiffer springs, higher compression and rebound damping and receives a larger diameter rear stabilizer bar to reduce body roll during cornering.
FRONT AND REAR SUBFRAMES
The CL's chassis rigidity and NVH benefit from its robust front and
rear subframes. In front, a perimeter frame consisting of a front
member, side members and a rear bulkhead beam is used to form a very
strong structure that contributes to overall chassis stiffness and
frontal and offset frontal impact resistance.
Like the front subframe, the rear subframe forms a large, rectangular-shaped perimeter frame and is made up of large cross section members and smaller stringers that locate the rear suspension and house the fuel tank. Both subframes are mounted to the body with rubber isolators that dampen vibration in the low- and mid-frequency ranges.
LOW ROLL CENTER
To help ensure precise and stable handling, the CL has been designed
with a lower roll center in its suspension geometry. The roll center
of the front suspension is 57 mm above ground level and 116 mm above
ground level in the rear.
HYDRAULIC ENGINE MOUNTS
To further isolate the cabin from vibration, the CL's 3.2-liter
engine is mounted to the subframe with two electronically controlled,
hydraulic engine mounts and a side stopper mount. The hydraulic
mounts are tuned to minimize vibration by transfer of fluid between
two hydraulic chambers in the mount, thereby changing the damping
frequency of the mount to help counter engine vibration.
STEERING
The steering must strike a balance between the isolation expected of
a premium coupe and the immediate, response of a pure sports car.
Both ends are served by the CL's power steering. With the assist
modulation based on engine speed, steering is light during low speed
maneuvering and gets progressively heavier as engine speed increases.
For more responsive steering, the new CL has a quicker steering ratio
as compared to the previous-generation CL.
To insulate the driver from road harshness without degrading steering precision, a rubber coupling is positioned in the bottom end of the steering column.
BRAKING SYSTEM
The new CL is equipped with larger diameter 11.8 in (300 mm)
ventilated front disc brakes with increased rotor thickness of 1.1 in
(28 mm) to provide confident braking power and fade resistance. In
addition, the CL now has a short ratio brake pedal to provide
immediate, consistent and predictable braking feel under all driving
conditions.
By separating the service and parking brakes in the rear wheels and increasing rotor diameter to 11.1 in (282 mm), further enhancements in brake performance were achieved. The new drum-in-disc brake design employs the disc portion of the unit for dynamic braking, while the drum is used only for the parking brake function. The parking brake is operated with a push on/off type floor pedal, maximizing center console space between the driver and passenger seats.
ANTI-LOCK BRAKING SYSTEM (ABS)
The CL's standard 4-wheel Anti-lock Braking System (ABS) enhances
steering control during hard braking. Speed sensors at each wheel
send signals to the ABS control module. When 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.
While the 3.2 CL features a three-channel ABS system, the Type S is fitted with a special four-channel system that works in conjunction with the VSA system. Both ABS systems operate in three-channel mode during straight-line braking, apportioning braking power to the front wheels independently and the rear wheels in tandem. This enhances the driver's ability to maintain steering control during panic stops on slick road surfaces.
The Type S ABS system automatically switches to a four-channel mode when the 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.
TRACTION CONTROL SYSTEM (TCS)
The standard equipment Traction Control System (TCS) on the CL coupe
detects wheel slip under acceleration and coordinates use of braking
and ignition retard to regain traction. For the Type S, TCS utilizes
sub-throttle and ignition retard as well as front braking and fuel
cut.
In situations where the front drive wheels are on different friction surfaces, such as when one drive wheel is on wet pavement while the other is on dry pavement, the system applies braking action to the wheel that's slipping, allowing the tire with better grip to move the vehicle. In addition, the system also reduces total engine power output to minimize wheelspin.
VEHICLE STABILITY ASSIST (VSA)
First equipped in 2000 on the Acura 3.5 RL flagship sedan, the Acura
Vehicle Stability Assist (VSA) system is standard equipment on the
3.2 CL Type S model. Similar to the 3.5 RL system, the CL's
Acura-designed system orchestrates the throttle and brakes to
seamlessly integrate traction control, anti-lock braking and
stability enhancement processes. This innovation is designed to
assist the driver in maintaining control during cornering,
acceleration and sudden collision-avoidance maneuvers by applying
brake force to the right or left front wheel as necessary and
managing the throttle and ignition systems.
By monitoring input from eight vehicle sensors, the VSA system 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 the predicted response range &endash; as when cornering forces exceed the tires performance, for example &endash; VSA automatically intervenes with corrective action. In the case of oversteer (which may lead to spin), VSA applies braking to the outside front wheel to counter the unintended yawing tendency. On the other hand, if understeer is detected, VSA applies braking to the inside front wheel and reduces engine power to turn the car back on to the intended course.
Unlike some vehicle stability systems, which can seem intrusive to enthusiast drivers, the Acura VSA is calibrated to add to stability and predictability, without stifling the driving enjoyment of the CL's carefully engineered chassis and double wishbone suspension. An indicator light flashes on the instrument panel while the system is actively enhancing the stability of the vehicle. A cockpit switch is provided to disable the VSA and TCS while leaving the antilock braking system fully functional.
WHEELS AND TIRES
With the enhanced performance capabilities of the new CL, tire and
wheel sizes were increased to accommodate the additional demands of
high performance driving. The 3.2 CL benefits from 6.5-inch wide x
16-inch diameter aluminum alloy wheels with the 205/60R16 Michelin
MXV4 all-season tires. The 3.2 CL incorporates an all-new seven-spoke
design with a five-bolt lug configuration for durability.
The 3.2 CL Type S sports aggressive 7-inch wide x 17-inch diameter aluminum alloy wheels. The 5-spoke layout incorporates an outer rimless design to achieve a seamless contour from the center of the wheel all the way out to the tire for an aggressive, sporty appearance. Large openings in the wheel ensure proper ventilation of the brakes. The Type S wheels are mounted with 215/50R17 V-rated, all-season, high-performance Michelin MXMV tires for excellent cornering capability.