2011 Acura TL - Chassis
9/22/2010 9:47:00 PM
The 2011 TL is engineered to live up to the highest standards for a performance luxury sedan. Both the TL and the TL SH-AWD® are rewarding and entertaining to drive, whether around town or on a long, winding road to adventure. When equipped with SH-AWD® the TL is as confidence inspiring on wet or snowy roads as it is on dry pavement, and standard Vehicle Stability Assist (VSA®) makes the drive even more secure.
Unlike some competitors (who add all-wheel-drive to their vehicles primarily to help conquer winter conditions) Acura's SH-AWD® system was designed to generate sporty handling in addition to delivering good winter-driving capabilities. This means that the TL SH-AWD® is inspiring to drive year-round. Research showed that customers in this segment want overall driving character first and that's the tuning priority the TL focuses on, while simultaneously maintaining all-season capability. The SH-AWD® system in the TL with 6-speed manual transmission TL features unique parameters to account for the manual transmission.
The SH-AWD® Advantage
Along with the larger engine, the TL SH-AWD® also gets suspension, brake and steering upgrades that further sharpen its performance. The SH-AWD® system is ideally positioned to lead the performance luxury sedan category where the TL competes, as 35-percent of all vehicles in the class have all-wheel-drive.
While the TL offers quick turn-in, flat cornering, a high level of grip and neutral handling characteristics when driven aggressively, with its more powerful engine and more sporting suspension tuning, the SH-AWD® model takes performance a step further to deliver racetrack-quality handling without losing the composure required of a daily driver.
A lightweight unit-body is the basis for a great-handling sport sedan, with low mass that allows for quick acceleration, aggressive cornering and excellent braking capability. Meanwhile, excellent structural stiffness helps deliver suspension and steering precision, an ultra-quiet interior and lasting durability. The TL meets all these objectives with sophisticated unit-body engineering that provides maximum stiffness as well as low weight through the use of the highest amount of high-strength steel in Acura history.
The use of aluminum for the construction of the hood, front and rear bumper beams, and instrument-panel beam helps reduce overall weight of the TL for improved acceleration, cornering, braking and fuel economy. A total of 51.7 lbs. is saved by the use of aluminum body components.
The Acura TL front suspension is double-wishbone design with coil spring, damper and stabilizer-bar rates tuned for performance handling while simultaneously retaining a flat, comfortable ride. Stamped-steel upper and cast-iron lower control arms hold a forged-steel steering knuckle, with the upper arms attaching to the unit-body via special low-vibration pivot bushings and the lower control arms attaching to an aluminum box-section subframe via specially tuned conventional pivot bushings and hydraulic compliance bushings. The subframe is connected to the unit-body via special vibration-reducing mounts. Nitrogen-charged dampers with special blow-off valves, coil springs, a stabilizer bar and a tubular steel shock tower brace complete the front suspension system.
The TL's multi-link rear suspension is similar to the system found in the Acura TSX. Like the front suspension, the independent rear suspension features stamped steel upper A-arms with increased roll center height, while two steel tubular links and a single toe link provide the lower control. The lower links are mounted to a floating sub-frame that reduces the intrusion of noise, vibration and harshness (NVH) into the TL cabin. A forged aluminum knuckle, nitrogen-charged dampers with special blow-off valves, coil springs and a stabilizer bar complete the rear suspension.
The rear suspension geometry controls camber gain 40-percent better than the previous TL while the body rolls during a tight corner, keeping a larger portion of the tire footprint on the ground for improved traction. Along with the TL's lower center of gravity, a higher rear roll center contributes to reduced overall body roll.
SH-AWD® SUSPENSION TUNING
The TL SH-AWD® has unique suspension tuning including special coil spring, damping and stabilizer-bar rates, and even special subframe mounting dampers all tuned for flatter cornering with reduced pitching motions under acceleration and braking. The system is also specifically tuned for the all-wheel-drive vehicle dynamics, as well as for the unique P245/45R18 tires fitted to the TL SH-AWD®. As a result, the TL SH-AWD® feels even more nimble than the front-wheel-drive TL during aggressive cornering.
"BLOW-OFF" DAMPER BYPASS VALVE
The TL has dual-stage hydraulic "blow-off" suspension dampers with specially integrated bypass valves. The purpose of this feature is to provide maximum damping for large inputs and reduce the damping for smaller inputs. This in turn gives the TL sharp handling performance while simultaneously filtering out unwanted road imperfections.
The TL SH-AWD® 6MT has unique dual-stage hydraulic "blow-off" suspension dampers that receive fine tuning for use with the 6MT model based on its lighter weight and more aggressive handling capabilities. The front dampers for the manual transmission equipped TL incorporate 5-percent more tension damping during low piston speeds to generate improved turn-in feel. In addition, the front dampers generate 14-percent less high speed compression damping which helps improve ride quality.
The TL uses hydro-compliant bushings on the lower front suspension wishbone to help reduce NVH. Rather than using a standard rubber bushing, the bushings are fluid filled, thereby significantly increasing the damping performance. This increased damping is particularly effective at improving ride quality and reducing brake judder vibration. Fluid-filled mounts are also used to isolate the transmission and engine.
HYDROFORMED STEEL REAR SUBFRAME
Road noise, vibration and harshness (NVH) is dramatically reduced through the use of floating rear subframe rails that carry the lower rear suspension links (and differential on the SH-AWD® model). The subframe is isolated from the body by specially tuned bushings, and uses hydroformed tubular steel side members for rigidity and a direct reduction of NVH in the passenger cabin. The hydroformed rails are created using hydraulic pressure that shapes steel tubing in a special mold. The result is light, strong and precisely shaped steel components that generate a reduction in rear chassis vibration.
ENGINE MOUNT SYSTEM
The Acura TL engine features a fluid-filled, hydro-compliant engine mount design that significantly reduces engine noise, vibration and harshness (NVH). The result is a 25-percent reduction in engine vibration, a substantial achievement that is noticeable and appreciated by the driver and passengers alike.
The TL SH-AWD® 6MT employs more performance minded engine and transmission bushings that better resist engine and/or transmission movement during aggressive handling. Engine side mount bushing stiffness increases by 80-percent, front mount rate increases by 17-percent, rear hydro mount firmness increases by 50-percent and the transmission upper mount is stiffened by 100-percent.
For TL SH-AWD® 6MT applications, special heavy-duty front driveshafts are used. In addition to being 2-percent larger in diameter (26.5 mm versus 26 mm), the driveshafts have a larger inboard spline size (32 mm versus 30 mm) and team with more heavy-duty CV joints.
HEAVY-DUTY FRONT DIFFERENTIAL
To account for the torque output of the new 3.7L V-6 and the sporting nature of the performance sedan, all TL SH-AWD® models make use of a heavy-duty front differential. As compared to the previous TL Type-S, the 2011 TL front differential uses a new forged housing constructed of higher grade forged-steel. In addition, the housing uses 18 retention bolts rather than 12 bolts as used with the TL Type-S differential housing. The result is a differential with an 18.8-percent higher torque rating.
4-WHEEL DISC BRAKES WITH EBD AND BRAKE ASSIST
The TL has 4-wheel disc brakes with Electronic Brakeforce Distribution (EBD) and Brake Assist. In front, 12.6-inch diameter radially-vented cast-iron front rotors are clamped by dual-piston calipers. At the rear, single-piston calipers are matched with 13.1-inch diameter solid rotors.
SH-AWD® Brake Upgrades
In keeping with its mission as a premium performance sport sedan, the Acura TL SH-AWD® features special front fascia-mounted cooling ducts for the front brakes and unique vacuum booster specifications. The system upgrades allow even more confident and consistent braking in repeated high-use conditions such as during spirited mountain road driving. Hill Start Assist (HSA) is also added to eliminate vehicle rollback when starting on a sloped surface.
ELECTRIC POWER STEERING (EPS)
Taking a cue from Acura's famed NSX supercar, the 2011 TL uses an advanced form of Electric Power Steering (EPS). The system is designed to provide outstanding steering feel and optimally calibrated steering assist for performance driving. In addition, the EPS helps improve TL fuel mileage by 0.7 mpg in the city and 0.8 mpg on the highway by eliminating parasitic power losses associated with a traditional hydraulic power steering pump. Principal components of the EPS system are a torque-sensing steering box, the electronic boost motor located as an integral part of the steering rack, and a dedicated electronic control unit.
The biggest advantage for EPS is the ability to specifically tune the steering feel to suit the enthusiast driver. Computer algorithms recognize the vehicle speed and provide low steering effort for parking maneuvers, then begin to firm up steering feel as speed increases to increasingly provide a more solid feel at higher speeds. The EPS tuning is unique for the SH-AWD®, featuring more pronounced steering effort build up at high speed.
With the 6-speed manual transmission TL SH-AWD®, the EPS system is further tuned to deliver a slightly heavier feel as speed increases thus generating more confident mid- to high-speed driving dynamics.
The EPS system on the TL requires 2.65 turns lock-to-lock. Curb-to-curb turning diameter is 38.4 feet a significant accomplishment considering the TL's long wheelbase.
WHEELS AND TIRES
Large-diameter aluminum wheels and wide tires further complement the TL's exterior design. Their design and finish are formulated to go with the TL's emotional body design, and TL customers can choose between three different wheel sizes, designs and finishes. The TL and TL with Technology Package come standard with 17x8-inch 10-spoke wheels, with 18x8-inch wheels available. The TL SH-AWD® and TL SH-AWD® with Technology Package have 18x8-inch 5-spoke wheels, with available 19x8-inch 10-spoke wheels for the TL SH-AWD® with Technology Package.
Acura TL tire choices include:
- Bridgestone Turanza EL400 P245/50R17 98V M+S (TL)
- Michelin Pilot HX MXM4 P245/50R17 98V M+S (TL with Technology Package)
- Michelin Pilot HX MXM4 P245/45R18 96V M+S (TL with Technology Package , TL SH-AWD® and TL SH-AWD® with Technology Package)
- Michelin Pilot Sport PS2 245/40ZR19 94Y (available summer tire for TL SH-AWD® with Technology Package)
The spare tire is a space- and weight-saving T135/80D17 temporary unit located under the carpeted floor in the trunk.
Tire Pressure Monitoring System (TPMS)
Every TL model includes Acura's Tire Pressure Monitoring System that warns the driver if the air pressure decreases significantly in any tire.
HILL START ASSIST
The TL SH-AWD® model has standard hill start assist that helps prevent the vehicle from rolling backwards when the driver switches from the brake to the accelerator while the vehicle is stopped on a hill. When the road incline exceeds an 8-degree threshold and the vehicle is fully stopped in any forward or Reverse gear (with engine torque holding the vehicle), hill start assist self activates. The hydraulic brake modulator is controlled by a longitudinal g-force sensor along with a wheel speed sensor and steering angle sensor. When hill start assist is active, the brakes automatically hold momentarily as the driver's foot lifts off the brake. The brakes are automatically released when the driver presses the throttle to make the vehicle move and sufficient drive torque is applied.
The 2011 TL is designed to be one of the quietest cars in its class. Both the front-drive and SH-AWD® versions offer significant reductions in NVH compared to the previous generation TL. But because many enthusiast drivers like to hear the engine and exhaust note when they're aggressively applying the throttle, the TL SH-AWD® exhaust system is tuned to have a sportier note to satisfy performance drivers.
Apart from a specific exhaust note on the TL SH-AWD®, Acura engineers focused intently on eliminating undesirable road noise. A highly rigid unit-body, special suspension and subframe bushings, precisely tailored spring and damper rates, and even details such as PVC undercoating and foam filled A-, B- and C-pillars, dramatically reduce unwanted noise. Additional noise-attenuation features include heat-molded felt inner liners for the rear fenders.
WEIGHT AND BALANCE
The addition of a manual transmission, an all-new clutch system and suspension changes yield an 88 pound reduction in weight on the front of the TL. The weight reduction not only delivers improved performance, but also generates a more favorable front/rear weight bias. Compared to an automatic transmission equipped TL SH-AWD®, the 6-speed manual version improves weight distribution by 1-percent thus generating a 58/42 ratio versus the 5AT's 59/41 ratio.
Acura conducted extensive validation testing of TL prototypes at numerous locations around the world. SH-AWD® tuning was conducted in New Zealand, testing on city streets was done in Southern California, corrosion performance evaluations were conducted in Nova Scotia, and snow and cold-weather testing was done in Minnesota as well as in Alaska. In addition, cooling and brake tests were performed in Death Valley, high-altitude testing was done in the Colorado Rockies, and performance tuning was conducted in Japan, at the famed Nürburgring circuit in Germany and at Virginia International Raceway, where the TL SH-AWD® proved highly competitive with its premium class competitors.
Acura engineers conducted extensive validation testing of the new 6-speed manual transmission equipped TL SH-AWD®. Whether driven on a roadway or racetrack, reliable performance was of equal importance as overall vehicle performance.
During testing and evaluation, Acura engineers spent much time analyzing and comparing the TL SH-AWD® 6MT to other vehicles in its competitive set. The TL falls in a unique category whereby it has more passenger/cargo volume than vehicles such as a BMW 3-series or Mercedes C-class, yet it is has less volume than a BMW 5-series or Mercedes E-class. However, based on the engineering goal to build a vehicle that would outperform competitive set sedans regardless of size or price, the TL SH-AWD® 6MT track testing focused on the best handling versions of each manufacturer's model. In all cases, this meant the smaller, lighter models (such as BMW 3-series).
|Acura TL SH-AWD® 6MT||3.7L V-6, 305 hp||AWD|
|Audi A4||2.0L I-4, 211 hp||AWD|
|Audi S4||3.0L V-6, supercharged, 333 hp||AWD|
|Audi A6||3.2L V-6, 255 hp||AWD|
|BMW 335i||3.0L I-6, twin-turbo, 300 hp||RWD|
|BMW 335xi||3.0L I-6, twin-turbo, 300 hp||AWD|
|BMW 535i||3.0L I-6, twin-turbo, 300 hp||RWD|
|Infiniti G37 Sport||3.7L V-6, 328 hp||RWD|
|Infiniti M35||3.5L V-6, 303 hp||RWD|
|Infiniti M35x||3.5L V-6, 303 hp||AWD|
|Mercedes C300 Sport||3.0L V-6, 228 hp||RWD|
|Mercedes C300 4Matic Sport||3.0L V-6, 228 hp||AWD|
|Mercedes E350 Sport||3.5L V-6, 268 hp||RWD|
|Mercedes E350 4Matic Sport||3.5L V-6, 268 hp||AWD|
TL SH-AWD® 6MT testing occurred at a variety of locations including Virginia International Raceway as well as at Honda R&D Americas' own Transportation Research Center (TRC) a 1.6-mile, 15-turn road course (designed by renowned track designer Alan Wilson) that was specifically built to highlight challenging handling characteristics including quick corner transitions along with increasing and decreasing radius turns.
The goal of the TL SH-AWD® 6MT was to generate an extremely neutral handling vehicle that provides great feedback to the driver along with excellent predictability. Often times, all-wheel-drive vehicles provide more available traction but are saddled with a heavier feel and a pronounced amount of understeer. With front-wheel-drive, typically there is a constant battle with understeer which dramatically hampers handling performance. Rear-wheel-drive traditionally delivers quick road course times, but requires a skilled driver to manage the constant transitions between understeer and oversteer. During testing, although the BMW 335i and Infiniti G35 Sport generated similar (yet slower) lap times, the driving level required to achieve the times came with a constant threat of an oversteer-generated spin-out. In short, a driver of average skill level will be able to drive the TL SH-AWD® 6MT much closer to its handling limits without fear of a spin as compared to if the same driving skill level were applied to any of the TL's competitors.
In lateral g-force acceleration testing on a 200-foot diameter dry skidpad, the TL SH-AWD® 6MT effortlessly outperformed all competitive set sedans as it generated an impressive 0.96 g in clockwise direction driving and 0.97 g in counterclockwise driving. For comparison, the TL SH-AWD® 6MT generates more lateral grip than some exotic supercars.
All said, the TL SH-AWD® 6MT proves highly competitive not only within its premium class competitorsregardless of engine size, transmission style, or drivetrain designbut also amongst much more powerful and more expensive sport edition sedans offered by competitors.
Standard active safety features on the TL include an Anti-lock Brake System (ABS), Vehicle Stability Assist (VSA®), Electronic Brake Distribution (EBD) and Brake Assist. VSA® is an electronic stability control system that continuously monitors lateral acceleration, steering wheel angle, wheel speed and yaw rate and then VSA® applies individual brakes and/or reduces engine power to help the driver retain directional control of the vehicle.