2007 Acura TL - Chassis
Torrance, Calif. 09/08/2006 --
The TL's front-wheel drive chassis provides significant benefits in a 5-passenger sedan. The overall package is lighter than if it were rear drive, there is more passenger room and the drivetrain is more compact. There are also important benefits in fuel efficiency.
With the introduction of the TL Type-S, the TL chassis now finds itself with multiple challengers. Also, whereas previously the TL's target was the BMW 530i Sport, a magazine comparison favorite, the 2007 TL lineup gives buyers the choice between two distinct models.
The TL is targeted toward buyers interested in a high-tech luxury sedan with excellent handling and chassis dynamics, but who also value a comfortable ride more than razor's-edge handling. The Type-S is aimed at buyers who want an increase in handling, braking and dynamic capability, but without making major sacrifices in ride comfort or interior noise.
Both share a rigid platform with a performance-tuned suspension and large tires. The large tire contact patches enhance braking and handling with all-season tires. The high-performance "summer" tires available on the Type-S boost acceleration, handling and braking capability even higher on both dry and wet surfaces.
As a result both the TL and Type-S have excellent dynamic properties. Both feel crisp and taut, corner flat and offer a high level of grip-even with four passengers aboard. With two separate TL models for 2007, chassis engineers were able to uniquely tune the suspensions for the different models' roles.
Noteworthy TL chassis enhancements include:
Suspension tuning to enhance ride comfort while maintaining handling performance
Front spring rates reduced by 7 percent from 2006 TL
Shock absorbers and compliance bushing retuned for ride comfort
Thicker hollow front anti-roll bar and new larger diameter hollow rear anti-roll bar
New rear subframe bushings for reduced NVH
Stiffer 17 x 8-inch aluminum-alloy wheels that result in less road noise
Underbody brake strake to reduce brake fade
Features exclusive to the TL Type-S include:
Increased damping rates for superior handling
Rear spring rate increased
A solid front anti-roll bar and thicker rear anti-roll bar
Damper mount stiffness increased 400 percent for enhanced response and feel
Exclusive master cylinder for enhanced brake feel
Brembo 4-piston front brake calipers
Available 235/45R17 Bridgestone Potenza RE 030 high-performance "summer" tires on automatic and manual transmission models
HYDROFORMED ALUMINUM-ALLOY SUBFRAME
The TL uses an all aluminum-alloy front subframe that carries the engine, transmission and lower suspension links.
The U-shaped subframe cradle is hydroformed. In this process, a single aluminum-alloy tube is inserted into an immensely strong die, which is locked closed before the tube is pressurized with water. The resulting component is lighter and stronger than a multi-piece component would be. The hydroformed cradle is then attached to aluminum-alloy corner brackets to form the complete subframe.
For 2007, the subframe has been redesigned to accommodate the new 5-speed automatic transmission and, in the Type-S, the new 3.5-liter V-6 engine. The lower transmission mount has been changed from two pieces to one piece, and the upper transmission mount has been redesigned as well. In addition, the bushings between the rear subframe and the chassis on the TL have been revised.
The TL and TL Type-S are equipped with a pair of special fluid-filled Electronic Control Mounts. Connected to the hydroformed aluminum-alloy subframe, they reduce vibration when the engine is idling.
The TL engine also has a side mount that helps control lateral movement. And on the Type-S with 6-speed manual transmission, a special damper further reduces engine-rocking motion when the driver lets the clutch out or shifts.
The TL front suspension is a double-wishbone system with a rigid stamped steel upper arm and a steel lower arm. The system is functionally related to the systems used on Formula One and Indy Cars, and permits the best combination of road holding, ride quality and packaging for the TL. The system uses coil-over shock absorbers that, unlike strut suspensions, are not stressed suspension members. This reduces suspension friction and improves responsiveness to bumps. Suspension camber gain is maximized through the use of a short upper arm, while steering feel is enhanced through a high placement of the lower arm.
The upper suspension arm is extremely rigid, which makes it less likely to transmit vibrations from road surface irregularities into the cabin as road noise. A special compliance bushing on the lower arm better absorbs bumps and improves ride quality. A steel bar connects the shock towers. Hollow, high-strength and lightweight, it enhances chassis solidity, steering precision and feel.
While the major geometry is shared between the TL and TL Type-S, the tuning of these components results in cars with significantly different steering and ride feel.
The TL's suspension has been retuned with an emphasis on ride comfort while maintaining excellent handling. Thus, the hollow front anti-roll bar has increased in size from 25.4 mm to 27.2 mm. Also, the front spring rate has been reduced by 7 percent compared to the 2006 model. The front compliance bushing and dampers have been retuned for improved ride comfort, resulting in improved ride comfort without increased roll and only a slight decrease in instrumented handling tests.
The Type-S suspension has been retuned for significant performance gains. The hollow front anti-roll bar is replaced with a 27 mm solid bar. Although a smaller diameter than the previous TL, the bar is significantly stiffer than the hollow 27.2 mm bar it replaces. Additionally, the front damping rate has increased significantly. The dampers on the Type-S have been tuned specifically for this vehicle's goal of refined handling. The result is increased road holding and enhanced stability with a reduced roll angle, with a minimal loss in ride comfort. Also, the damper mounts are 400 percent stiffer, improving steering response and handling, but without compromising road noise isolation.
The TL rear suspension is a 5-link independent system with struts and coil springs. It mounts to a steel subframe to improve road isolation and provide a quiet interior. The rear suspension geometry adds "toe-in" when the suspension is compressed, improving handling stability over bumps and during hard cornering and braking.
A stabilizer bar further improves handling precision by limiting body roll, while a special "pillow joint" for the lateral links improves camber rigidity. Rubber shims on the leading and trailing arm bushings improve ride comfort.
As on the front suspension, the rear suspension has been specially retuned on both the TL and TL Type-S. The TL has unique shock valving for improved ride comfort. The rear anti-roll bar has been changed from a solid 17 mm bar on the 2006 model to a hollow 18.3 mm bar. This reduces weight without sacrificing roll stiffness.
Type-S suspension settings are tuned for performance. Although the automatic and manual transmission Type-S models have the same suspension settings, the rear spring rate has been increased 33 percent on vehicles equipped with a manual transmission, 14 percent on vehicles mated with automatic transmissions. The solid rear anti-roll bar has increased in size from 17 mm on the 2006 model to 20 mm for 2007 on cars with an automatic transmission. This results in much greater roll stiffness in the rear, allowing for better balance and control.
The TL uses torque-sensing, variable power-assisted rack and pinion steering. The engine-driven variable-output pump provides the kind of steering feel that driving enthusiasts like: modest steering effort at low speeds and precise feel at higher speeds.
For 2007, the TL Type-S receives revised power steering pumps and steering gearboxes to improve steering effort build and feeling while maintaining a confident and stable feel. To this end, the power steering pump has been retuned for decreased flow at 3250 rpm for increased effort build up. Additionally, the steering gearbox tuning increased effort by 15 percent at high speeds for better on-center feel. The rack has also been retuned for better damping feel. To keep up with the demands of spirited driving, the TL Type-S also features a new aluminum power steering fluid cooler.
Hydraulic steering dampers built into the system further improve stability during cornering and at high speeds. A one-way kickback valve decreases kickback to the steering wheel that can be caused by road irregularities. The hydraulic valve closes when it senses road irregularities, impeding disturbances to the steering wheel.
Increasing the stiffness of the steering gearbox mounting and the rear sub frame also maximizes steering linearity.
Both the TL and TL Type-S feature 4-wheel disc brakes with Electronic Brake force Distribution (EBD), Brake Assist, an anti-lock braking system (ABS) and 4-channel Vehicle Stability Assist (VSA) with Traction Control System (TCS) as standard equipment.
On the TL, the front brakes are ventilated 300 mm cast-iron discs with single-piston calipers. For 2007, fade resistance has been improved with a larger brake strake in the front fascia, which directs more air to the brakes. This reduces brake temperature in high-demand braking, and helps improve the TL's brake fade resistance. The rear brakes are 282 mm solid discs, gripped by single piston calipers.
Both manual and automatic transmission TL Type-S models receive 310 mm Brembo brake rotors and aluminum-alloy front brake calipers that previously were only available on manual transmision-equipped cars. The calipers have four pistons each and more aggressive pad material to offer improved brake feel and reduced fade in hard, repeated brake applications. They are also 30 percent lighter than the standard calipers, reducing unsprung weight by 4.3 pounds per wheel, which in turn improves suspension response for better ride and handling. The calipers feature an attractive black painted finish with the Acura name. Rear brakes are the same 282 mm solid discs as the TL, but the calipers are given a black finish to match the front brake calipers.
All models use a single 10-inch vacuum booster is used to reduce weight, increase stiffness and deliver more direct braking feel. Inside, the parking brake handle has been restyled with a new leather cover.
Electronic Brake Force Distribution
The TL features Electronic Brake Force Distribution (EBD), which continuously and automatically adjusts the pressure distribution between the front and rear brakes depending on how the vehicle is dynamically loaded.
Brake Assist comes standard on the TL. Its purpose is to help the driver apply full braking pressure in a "panic stop" situation. To do so, a microprocessor continually analyzes and "learns" the driver's normal braking habits.
In an emergency braking situation when the brakes are suddenly applied and partially released by the driver to avoid wheel lockup, brake assist helps the driver apply full braking force via the anti-lock actuator. A pressure sensor detects an increase in brake fluid pressure and activates the anti-lock braking system. Braking pressure is maintained momentarily after the driver's initial braking action unless the driver completely releases the brake pedal.
Anti-lock Braking System
Standard on the TL is a three-channel Anti-lock Braking System (ABS), which works in conjunction with the Vehicle Stability Assist(TM) (VSA(R)) system. Utilizing speed sensors located at each wheel, the system modulates braking power to the front wheels independently and to the rear wheels in tandem-enhancing driver control during maximum-effort stops. For 2007, a new ABS modulator improves response time and reduces noise when operating.
VEHICLE STABILITY ASSIST(TM) (VSA(R))
The TL is equipped with 4-channel Vehicle Stability Assist(TM) (VSA(R)) that helps the driver retain control of the car in the event the vehicle reaches its dynamic traction limits. For example, this may occur through aggressive cornering, encountering ice or dirt on the road, or entering a decreasing-radius corner too fast.
In the event of understeer, the system can apply the inside front and rear brakes to increase yaw, slowing the vehicle and enabling it to complete the turn. Engine torque may also be reduced by coordination of the Drive-by-Wire Throttle System(TM) and powertrain control module.
The 4-channel system controls all four brakes independently. In the event of oversteer (where the rear tires lose grip), the system can apply the outside front and rear brakes to decrease yaw, slowing the vehicle and enabling it to stay on its intended path.
An indicator light on the instrument panel alerts the driver whenever the VSA system is actively enhancing the vehicle's stability.
The traction control component of VSA uses sensors that monitor each of the wheels and a computer-controlled modulation of engine power and front brakes to help prevent wheel spin when starting out or accelerating. If the sensors detect wheel spin, traction control reduces engine power and applies brake force to the affected wheels. This helps the TL maintain traction during acceleration and helps the driver retain steering control, even when accelerating on slippery surfaces.
A cockpit switch is provided to disable the vehicle stability and traction control aspects of the system while leaving the ABS system fully functional.
The Acura TL has lightweight 17 x 8-inch aluminum-alloy wheels with distinctive designs for the TL and TL Type-S. The TL receives a split-five spoke wheel finished in Blade Sliver, while the Type-S wheels are a 10-spoke design finished in Dark Euro Silver. Both wheels are lightweight designs, which contribute to quicker suspension movement and better ride quality by contributing to lowering unsprung weight. Optional 18-inch aluminum alloy wheels are available as accessory in three different finishes.
Bridgestone 17-inch all-season high-performance tires were specifically developed for the TL. The standard tire is P235/45R17 M+S (all-season), and is available on TLs without the navigation system. TLs with navigation receive Michelin all-season high-performance tires. All Type-S models are equipped with Michelin tires, and a high-performance 235/45R17 Bridgestone Potenza RE-030 "summer" tire is available for the Type-S as well. The 2007 TL is also equipped with a tire pressure monitoring system.
The 17-inch tires significantly contribute to the TL design objectives including its aggressive, athletic appearance. They also measurably improve handling and braking.
The high-performance tires available on the Type-S further enhance dry handling, wet handling and braking, at the cost of performance in snow and accelerated wear. In warm weather, these tires consistently outperform all-season tires in slalom speed, maximum cornering g force, and braking distance.
The TL Type-S has a T145/70R17 temporary spare tire. A T135/80R16 temporary spare is used on the TL. The advantages of a temporary spare include maximum trunk space as well as reduced vehicle weight for better handling and fuel economy.
AVAILABLE TL Sport Suspension
Specifically made for TL models, an available dealer-installed sport suspension kit can also be purchased, which includes all four shock absorbers and springs, larger wheels and tires plus aero components. Known as the A-SPEC kit, it provides firmer damping and spring rates for an even sportier handling and offers a lower ride height, further distinguishing the TL.
The A-SPEC kit includes:
Pre-assembled performance springs and shocks that lower the vehicleapproximately 1.2 in. (30 mm)
18-inch wheels with 235/40ZR18 Yokohama AVS ES100 tires
Special steering wheel with distinctive shape and stitching
Performance brake pads (for automatic transmission vehicles only)