The Temple of VTEC - Honda and Acura Enthusiasts Online - Articles

INTRODUCTION

For the first time ever in an Acura vehicle, the 2009 TL is available in a choice of front-wheel-drive TL or all-wheel-drive TL SH-AWD� configurations. Replacing the previous TL Type-S is the TL SH-AWD� model, built exclusively for the enthusiast driver and featuring Super Handling All-Wheel Drive�, special suspension and steering tuning and the most powerful engine ever from Acura.

Not resting on its laurels, Acura will further up its game with an even more performance minded model for those drivers who prefer the interesting route over the direct route. Available for the 2010 model year will be a TL SH-AWD� with 6-speed manual transmission. However, the special TL goes well beyond the addition of a new transmission. Acura engineers developed a complete performance package that includes numerous enhancements to handling, steering and reliability.

Not only is this new manual transmission model the best performing Acura TL ever, but it is the top performer in handling amongst every vehicle in its class.

TL SH-AWD 6MT FEATURES

All-new close-ratio 6-speed manual transmission
All-new clutch system with increased holding, reduced pedal effort and better feel
Exclusive tuning for the Super Handling All-Wheel Drive� (SH-AWD�) system
Exclusive rate front coil springs
Exclusive rate front dampers
Stiffer engine and transmission mounts and brackets
Heavy-duty front driveshafts and CV joints
Heavy-duty front differential
Unique Electric Power Steering (EPS) tuning
Hill Start Assist (HSA) function exclusively designed for the 6-speed manual
Overall reduction in vehicle weight
Improved front/rear weight distribution
Available 19x8-inch diameter aluminum wheels with 245/40ZR19 summer tires

ENGINE

The 2010 TL SH-AWD� 6MT is powered by Acura's new 3.7-liter SOHC V-6. With 305 horsepower and 273 lbs-ft of torque, the V-6 engine is as powerful as some V-8s, and is the most powerful engine ever offered in an Acura. Compared to the previous generation TL Type-S 3.5-liter V-6 engine, the new 3.7-liter V-6 gains 19 horsepower and 17 lbs-ft of torque. The 3.7L engine features a new VTEC� valvetrain system that now varies the lift and duration of the exhaust valves (just as done for the intake valves) which contributes to increased power output and reduced emissions. The 3.7L engine is even lighter than the 3.5L powerplant it replaces, due in part to the use of aluminum rather than iron cylinder liners.

CLOSE RATIO 6-SPEED MANUAL TRANSMISSION

The availability of a 6-speed manual transmission for the 2010 TL SH-AWD� represents the first time Acura has ever paired its acclaimed Super Handling All-Wheel Drive� system with a manual gearbox. In addition to providing more gear choices (six forward gears versus five) compared to the TL's Sequential SportShift 5-speed automatic transmission, the new close ratio 6-speed manual transmission is approximately 110 lbs lighter in weight to further benefit acceleration, deceleration and handling.

In creating the all-new manual transmission, the first task for Acura engineers was to study the 6-speed manual transmission used with the 2008 TL Type-S to determine its strengths and weaknesses. The most significant design change involved engineering a new manual transmission that allowed the transfer of power to the SH-AWD� rear differential in addition to power being sent to a traditional front differential. However, because the new transmission would be paired with the largest and most powerful engine in Acura history, additional modifications were required to handle the increased torque output of the new 3.7L engine. In addition, since the 6-speed transmission was an all-new design, Acura engineers had the opportunity to choose exclusive gear ratios that best matched the specific parameters of the TL SH-AWD� 6MT model including its more performance minded suspension, lighter overall weight and improved front/rear ratio of weight balance.

The new 6-speed transmission uses a heavy-duty die-cast aluminum case that houses a mainshaft that is 14-percent larger in diameter compared to the mainshaft used with the TL Type-S 6-speed manual transmission. First through Fourth gears employ more closely spaced ratios for improved acceleration and passing power while Fifth and Sixth gears utilize ratios designed to deliver relaxed cruising. The gears feature improved design including being treated to glass beading and water jet blasting to smooth the outer metal surface as well as to reduce any possible stress risers. First gear synchronizers are now a triple cone design, Third and Fourth gear synchros feature 5.9-percent higher torque capacity, Fifth and Sixth gear synchros feature 9.1-percent higher torque capacity and the gearbox delivers an improved shifting feel.

The new 6-speed transmission is actuated by a cable-operated short-throw shifter mechanism. Capped by a leather-wrapped, Euro-stitched shift knob with integrated silver trim ring, the shifter delivers confident shifting combined with low shift effort.

NEW HIGH PERFORMANCE CLUTCH

Acura engineers designed an entirely new clutch system for the new 6-speed manual transmission fit to the 2010 TL SH-AWD�. In addition to generating increased holding ability and improved modulation, the clutch was also designed to deliver noticeably

better ease of use. With regards to modulation and feel, numerous Acura/Honda clutch designs were analyzed along with analysis of competitor vehicles including top European sports sedans.

With the new dual-mass clutch system, special consideration was paid to the actuation associated with repeated engagement/disengagement as experienced during heavy traffic while commuting. Moreover, increased emphasis was placed on developing a clutch with extremely constant pedal effort throughout the points of (dis)engagement during the stroke of the pedal. By keeping the effort linear, the driver has improved feel that results in better clutch interaction in all driving situations.

The new clutch design features a unique self-adjusting mechanism� thus, clutch "feel" does not change as the clutch disc wears. Rather than using a traditional pivot-lever fork-style arm to actuate the clutch throw-out bearing, the 6-speed's clutch system uses a hydraulic throw-out bearing assembly that generates substantially improved pressure distribution to the clutch diaphragm release levers.

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 tuned specifically for the all-wheel drive vehicle dynamics, as well as for the unique performance tires on the TL SH-AWD�. As a result the TL SH-AWD� feels even more nimble than the front-wheel-drive TL in aggressive cornering situations.

DUAL-STAGE "BLOW-OFF" DAMPER BYPASS VALVE

The 2010 TL SH-AWD� 6MT has unique dual-stage hydraulic "blow-off" suspension dampers with specially integrated spring bypass valves. The dampers are similar to those used on the TL SH-AWD� but receive further 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.

HYDRO-COMPLIANT BUSHINGS

The Acura TL engine features a new 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.

HEAVY-DUTY DRIVESHAFTS

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 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 differential. As compared to the previous TL Type-S, the differential uses a new forged housing constructed of higher grade forged-steel. In addition, the new 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.

ELECTRIC POWER STEERING (EPS)

Taking a cue from Acura's famed NSX supercar, the new 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 of EPS is the ability to specifically tune the steering to suit the enthusiast driver. Computer algorithms recognize the vehicle speed and provide low steering effort for parking maneuvers, then begin to firm up as speed increases to increasingly provide a more solid feel and linear response 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.

WHEELS AND TIRES

The TL SH-AWD� 6MT features standard 18x8-inch diameter 5-spoke aluminum wheels with Michelin Pilot HX MXM4 P245/45R18 M+S tires. Performance enthusiasts should consider the available 19x8-inch diameter 10-spoke aluminum wheels that are matched with Michelin Pilot Sport S2 245/40ZR19 summer tires. The 19-inch wheel/tire combination delivers noticeably improved handling performance with an exceptionally small increase in NVH.

WEIGHT AND BALANCE

The addition of a manual transmission, an all-new clutch system and suspension changes yield an 88 lb. 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.

HILL START ASSIST

The TL SH-AWD� 6MT model has a specially calibrated Hill Start Assist system that helps prevent the vehicle from rolling backwards when the driver switches from the brake to the accelerator while stopped on a hill. When the road incline exceeds an 8-degree threshold and the vehicle is fully stopped, hill start assist automatically 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 for one second as the driver's foot transitions from the brake pedal to the accelerator pedal. Hill Start Assist works with the VSA� modulator and will hold the vehicle for up to one second. The brakes are automatically released when the driver presses the throttle and the vehicle begins to move forward.