2011 Acura TL - Powertrain

POWERTRAIN OVERVIEW

The 2011 Acura TL and TL SH-AWD® are each fitted with a transversely mounted V-6 engine that has been engineered to meet the specific requirements of each TL model. The TL features an all-aluminum 3.5-liter V-6 with single overhead camshaft cylinder heads and 24 valves— with the intake valves actuated by Acura's VTEC® (Variable Valve Timing and Lift Electronic Control®) system. This compact and efficient engine produces 280 horsepower and 254 lbs-ft of torque.

The TL SH-AWD® is powered by a 3.7-liter V-6 that shares many features with the 3.5-liter engine, but gains displacement through larger cylinder bores and increased stroke. With 305 horsepower and 273 lbs-ft of torque, the 3.7-liter engine is as powerful as some V-8s, and is the most powerful engine ever offered in an Acura. The TL SH-AWD® engine features a VTEC® system that varies the exhaust valves as well as the intakes to contribute to elevated power output. The 3.7L engine is even lighter than the 3.5-liter engine, due in part to the use of aluminum (rather than iron) cylinder liners.

Both V-6 engines reflect Acura's unwavering commitment to the environment with good fuel efficiency given their power output. All TL engines meet EPA TIER 2 - BIN 5 and CARB LEV II ULEV standards, and make use of close-coupled catalytic converters to ensure efficient cold-start emissions control.

The standard transmission in the TL is a Sequential SportShift 5-speed automatic transmission operated by a straight-gate style console-mounted shifter. For more spirited driving, a racing-inspired steering wheel paddle shifter system is standard and works when the transmission is in "Drive" or "Sport".

For driving enthusiasts, available on the TL SH-AWD® is a close ratio 6-speed manual transmission with a heavy-duty clutch system. In addition to providing more gear choices (six forward gears versus five) compared to the TL's Sequential SportShift 5-speed automatic transmission, the 6-speed manual transmission is approximately 110 lbs lighter in weight to further benefit acceleration, deceleration and handling.

Since its original introduction, the TL has been exclusively a front-wheel-drive vehicle. Beginning with the fourth-generation 2009 model, an all-wheel-drive version joined the TL lineup. The TL SH-AWD® model features Super Handling All-Wheel Drive™, Acura's advanced drivetrain system that delivers quick, precise all-wheel-drive response. SH-AWD® is the first all-wheel-drive system to distribute the optimum amount of torque not only between the front and rear axles, but also between the left and right rear wheels. The system's unique torque vectoring generates direct yaw control to make the TL SH-AWD® exceptionally neutral under power, for greater handling precision and control.

  2011 TL 2011 TL SH-AWD® 2011 TL SH-AWD® 6MT
Engine SOHC VTEC® (intake) V-6 SOHC VTEC® (intake and exhaust) V-6 SOHC VTEC® (intake and exhaust) V-6
Displacement 3.5-liter (3471 cc) 3.7-liter (3664 cc) 3.7-liter (3664 cc)
Compression ratio 11.2:1 11.2:1 11.2:1
Fuel type Premium Unleaded Premium Unleaded Premium Unleaded
Horsepower @ rpm 280 @ 6,200 305 @ 6,300 305 @ 6,300
Torque @ rpm (lbs-ft) 254 @ 5,000 273 @ 5,000 273 @ 5,000
Transmission 5 AT 5 AT 6 MT
EPA estimated mileage (city/highway) 18/26* 17/25* 17/25*
Emissions certification EPA TIER 2 - BIN 5 and CARB LEV II ULEV EPA TIER 2 - BIN 5 and CARB LEV II ULEV EPA TIER 2 - BIN 5 and CARB LEV II ULEV

*Based on 2011 EPA mileage estimates. Use for comparison purposes only. Do not compare to models before 2008. Your actual mileage will vary depending on how you drive and maintain your vehicle.

Powertrain at a Glance

Acura TL

  • Front-wheel-drive (FWD)
  • 3.5-liter, SOHC, aluminum V-6 engine
  • 280 hp at 6,200 rpm and 254 lbs-ft of torque at 5,000 rpm
  • 11.2:1 compression ratio
  • Variable Valve Timing and Lift Electronic Control (VTEC®) for intake valves
  • Lightweight magnesium alloy intake manifold with dual-stage induction system
  • Cold-air intake system
  • Integrated exhaust manifolds cast directly into the cylinder heads
  • Drive-by-Wire™ throttle system
  • Sport-tuned exhaust system with dual tips
  • Computer-controlled Programmed Fuel Injection (PGM-FI)
  • Direct ignition system
  • Detonation/knock-control system
  • Maintenance Minder™ system
  • 100,000 mile tune-up intervals*

*Does not apply to fluid and filter changes. Exact mileage is determined by actual driving conditions.

TL SH-AWD® and TL SH-AWD® 6MT

  • SH-AWD® drivetrain for performance handling and all-season capability
  • 3.7-liter, SOHC, aluminum V-6 engine
  • 305 hp at 6,300 rpm and 273 lbs-ft of torque at 5,000 rpm
  • 11.2:1 compression ratio
  • High-silicon aluminum cylinder sleeves cast directly into the cylinder block
  • Variable Valve Timing and Lift Electronic Control (VTEC®) for both intake and exhaust valves
  • Lightweight magnesium alloy intake manifold with dual-stage induction system
  • Cold-air intake system
  • Drive-by-Wire™ throttle system
  • Integrated exhaust manifolds cast directly into the cylinder heads
  • High-flow, sport-tuned dual exhaust system with quad exhaust tips
  • Computer-controlled Programmed Fuel Injection (PGM-FI)
  • Direct ignition system
  • Detonation/knock control system
  • Maintenance Minder™ system
  • 100,000-mile tune-up intervals*

*Does not apply to fluid and filter changes. Exact mileage is determined by actual driving conditions.

Emissions (3.5L and 3.7L engines)

  • High-flow close-coupled catalytic converters plus under-floor catalytic converter
  • High-capacity 32-bit RISC processor emissions control unit
  • Meets EPA TIER 2 - BIN 5 and CARB LEV II ULEV emissions standards

Fuel Economy

  • TL: EPA estimated 18/26/21 mpg (city/highway/combined)
  • TL SH-AWD: EPA estimated 17/25/20 mpg (city/highway/combined)
  • TL SH-AWD 6MT: EPA estimated 17/25/20 mpg (city/highway/combined)

*Based on 2011 EPA mileage estimates. Use for comparison purposes only. Do not compare to models before 2008. Your actual mileage will vary depending on how you drive and maintain your vehicle.

Noise, Vibration, and Harshness (NVH) control

  • 60-degree cylinder V-angle for smooth running
  • Automatically tensioned, maintenance-free serpentine accessory belt drive
  • Electric Power Steering (EPS) eliminates hydraulic pump noise
  • Electronically controlled hydraulic engine mounts reduce vibration

Sequential SportShift 5-speed automatic transmission

  • Quick-response Sequential SportShift allows for semi-manual operation
  • Straight-gate style console-mounted shifter
  • Racing-inspired, steering-wheel-mounted paddle shifters
  • Paddle shifters functional in Drive and Sport modes
  • Coordination between Drive-by-Wire™ throttle system and Sequential SportShift transmission makes for quick, smooth shifts
  • Wide gear-ratio spacing for quick acceleration combined with good fuel economy
  • Advanced Shift Hold Control minimizes unwanted shifting during spirited driving
  • Grade Logic Control System reduces gear hunting when climbing hills

6-Speed manual transmission

  • Heavy-duty die-cast aluminum case
  • Exclusive gear ratios matched to the specific parameters of the TL SH-AWD® 6MT
  • Heavy-duty clutch system with exceptional holding, low pedal effort and excellent feel
  • Cable-operated short-throw shifter mechanism
  • Leather-wrapped, Euro-stitched shift knob with integrated silver trim ring
  • 110 lbs lighter weigh compared to 5-speed automatic transmission

Super Handling All-Wheel Drive™ (TL SH-AWD®)

  • Fully automatic full-time traction and handling system
  • Distributes torque between front and rear axles
  • Distributes torque between left and right rear wheels
  • Provides torque vectoring to directly control the yaw moment of the vehicle
  • Capable of "overdriving" rear wheels to enhance handling
  • Understeer is greatly reduced during hard cornering
  • Increases overall cornering ability in dry and inclement weather 

ENGINE ARCHITECTURE

The TL's 3.5-liter V-6 engine uses an inherently smooth-running 60-degree V-angle. The cylinder block is constructed of aluminum and has cast-in iron cylinder liners. The cylinder heads are cast of lightweight aluminum and feature four valves per cylinder along with a 2-rocker VTEC® valve timing system, with variable lift for the intake valves. An 11.2:1 compression ratio, high-output port shapes, intake airflow enhancements and a sport-tuned exhaust system team to enhance power. In addition to a high specific power output (280 hp at 6,200 rpm), the 3.5-liter V-6 delivers exceptional refinement and low emissions.

The 3.7-liter engine in the TL SH-AWD® is the most powerful engine ever fitted to an Acura sedan. While dimensionally similar to the compact 3.5-liter TL engine, the 3.7-liter employs aluminum (rather than iron) cylinder liners for weight savings and improved cooling. Its VTEC® rocker arm system features variable lift and timing for both intake and exhaust valves. A free breathing intake system, a high compression ratio, a high-flow exhaust system using close-coupled catalytic converters and dual exhaust pipes team make the 3.7L engine's power output exceptionally linear and smooth.

ENGINE BLOCK

Both the 3.5-liter and the 3.7-liter engine blocks are constructed of lightweight die-cast aluminum. The 3.5-liter engine has thin-wall iron cylinder liners that are made in a centrifugal spin-casting process that ensures high strength and low porosity. The rough outer surface of these liners makes for an effective bond with the aluminum block, generating good block stiffness and heat transfer from the liners to the block.

The 3.7-liter engine cylinder liners are made of high-silicon aluminum and are cast directly into the aluminum block. The hard piston ring sealing surface of the liners is created during manufacturing with a mechanical etching process that exposes silicon particles embedded in the sleeves. The aluminum sleeves provide better cooling thus allowing closer piston-to-cylinder clearance than iron liners afford. The alloy liners also improve heat dissipation in the area between adjacent cylinder bores, allowing the 3.7-liter engine to have larger cylinder bores, even though its bore-center dimensions (the distance between the centers of adjacent bores) is the same as the 3.5L V-6.

Both the 3.5-liter and the 3.7-liter cylinder blocks are heat-treated for strength and have deep-skirt designs with four bolts per bearing cap (providing excellent structural support for the crankshaft), thus minimizing engine noise and vibration.

CRANKSHAFT/CONNECTING RODS/PISTONS

The 3.5-liter engine of the TL and the 3.7-liter engine of the TL SH-AWD® both employ robust forged-steel crankshafts for high strength and minimum weight. On both engines, forged aluminum pistons are cooled with oil spray directed up to the underside of the piston crowns, making possible the high 11.2:1 compression ratio. The connecting rods are steel forgings for high strength, and are "crack separated"— a unique process in which the bearing caps are broken away from the rod rather than machined separately. This process forms a lighter, stronger connecting rod with perfect mating surfaces.

CYLINDER HEADS/VALVES

Both the 3.5-liter and the 3.7-liter engines have lightweight aluminum cylinder heads that are pressure cast for high accuracy and low porosity. To save weight and reduce parts count, these cylinder heads have integrated exhaust-port castings that provide optimal positioning for close-coupled catalytic converters— one located on each cylinder bank. This design results in more rapid "light off" of the catalytic converters during cold start-up for reduced start-up emissions. The cylinder heads are sealed against the block with a special 3-layer shim-type head gasket.

Each cylinder head uses a single camshaft, turned by an Aramid-fiber reinforced toothed drive belt for long service life. Compared to the camshafts used in the previous 3.7L V-6 (fit to the MDX), the 2011 TL's 3.7L camshaft lobes deliver more lift (4-percent more on intake, 10-percent more on exhaust), more valve opening duration (4-percent more on intake, 14-percent more on exhaust), and increased intake/exhaust valve overlap. In addition, valve timing has been optimized for the TL's intake and exhaust systems.

Intake port design on the 3.7-liter SH-AWD® engine has been improved enough that the new ports alone add seven horsepower versus earlier designs. Compared to the 3.5L V-6, intake valve weight has been reduced 13-percent due to removal of material from the valve head.

VTEC® (VARIABLE TIMING AND LIFT ELECTRONIC CONTROL)

The 3.5-liter TL engine uses the VTEC® system, providing crisp throttle response, strong low-speed torque and enhanced high-rpm power. This is achieved by providing reduced intake valve lift and duration at low engine speeds for good torque, with increased valve lift and duration at higher speeds for optimum power. With the VTEC® system, both intake valves are controlled by a single low-speed camshaft lobe.

At 4,750 rpm the Powertrain Control Module (PCM) electronically triggers the opening of a spool valve that routes pressurized oil to small pistons within the intake valve rocker arms. Moved by this pressurized oil, the pistons lock together each cylinder's intake rocker arms, which then follow in unison a single high-lift, long-duration cam lobe. Intake valve lift and opening duration are adjusted according to engine speed, resulting in the 3.5-liter TL having a broad torque curve as well as excellent power at peak rpm.

The 3.7-liter engine in the TL SH-AWD® features a further refined version of VTEC®. This system provides two-mode control of the exhaust as well as the intake valves, so all 24 of the engine's valves are VTEC® controlled. Moreover, operation of all the engine's valves are controlled for optimal volumetric efficiency, air/fuel mixing, burn rate and exhaust flow.

The 3.7-liter engine has the same VTEC® intake valve control system as the 3.5-liter engine, but adds a unique multi-arm VTEC® rocker arm system for the exhaust valves. Both exhaust valves follow a single low-lift, short-duration cam profile at low engine rpm. As engine rpm rise, pressurized oil (controlled by the PCM) activates small pistons that lock the exhaust valve rocker to a corresponding high-speed rocker arm, which then follows a single high-lift, long-duration cam lobe.

On the 3.7-liter engine, the transition to high-lift mode occurs at 4,700 rpm, where intake valve lift increases 28-percent and exhaust valve lift increases 10-percent. Valve opening duration increases 35-percent on the intake side and 11-percent on the exhaust side, increasing valve overlap by 47-percent over the intake-only VTEC® system. The 3.7L V-6's VTEC® system provides further improved power and torque, even lower emissions and better fuel efficiency.

DRIVE-BY-WIRE™ THROTTLE SYSTEM

The TL and the TL SH-AWD® do not use conventional mechanical throttle linkages, but instead employ sophisticated electronics to provide the connection between the throttle pedal and the engine's throttle-body. The result is more accurate and precise throttle control, along with less clutter and reduced weight under the hood. By programming such factors as "gain" and "tip-in" into the throttle actuation, engine response and drivability can be tailored to suit specific driving conditions. The 3.5L and 3.7L engines use different drive-by-wire throttle calibration curves to suit the characteristics of each powertrain.

Acura's high-tech Drive-by-Wire™ throttle system monitors pedal position, throttle-body opening, engine rpm and road speed to establish driving conditions in real time. This data is used to define the throttle control sensitivity necessary to provide the predictable and responsive feel corresponding to driver expectations.

The Drive-by-Wire™ throttle system also helps integrate engine functions with the Vehicle Stability Assist™ (VSA®) and traction control system. To smooth downshifts, when the Sequential SportShift transmission is in Sport mode the system is programmed to "blip" the throttle to help match engine speed to gear speed within the transmission.

COLD AIR INDUCTION SYSTEM

The TL and TL SH-AWD® use a cold air induction system that pulls intake air from the left side of the grill, ahead of the radiator, ensuring that incoming air is as much as 65 degrees F cooler than underhood air in the engine compartment. Cool air is denser and contains more oxygen per volume than warmer air, enabling the engine to make more power. Carefully designed ducting routes fresh air to the sealed air cleaner assembly and then on to the throttle-body. The 3.5-liter engine has a 64 mm diameter throttle-body, while the 3.7-liter engine uses a special 69 mm diameter throttle-body that generates a 12-percent flow increase.

PROGRAMMED FUEL INJECTION (PGM-FI)

The Programmed Fuel Injection (PGM-FI) system continuously tracks many engine parameters including crankshaft and camshaft positions, throttle position, intake air temperature and mass flow rate, engine coolant temperature, and manifold pressure (and airflow volume) and then the system adjusts fuel delivery accordingly to deliver the best combination of power, fuel economy and low emissions.

MULTI-HOLE FUEL INJECTORS

Special multi-hole fuel injectors mounted in the lower portion of the intake manifold spray directly toward the intake ports. The multi-hole injector design enables the reduction in fuel droplet size to generate better fuel atomization, resulting in improved cold weather start-up, better fuel economy, reduced emissions and improved power.

2-PIECE DUAL-STAGE INTAKE MANIFOLD

Both TL engines feature a dual-stage intake manifold made from lightweight magnesium-alloy. The manifold works in concert with VTEC® to improve low-speed torque with no sacrifice in high-rpm power. Divided into two banks feeding three cylinders per bank, the manifold has two Powertrain Control Module-controlled butterfly valves located between each bank. These closed valves separate bank-to-bank plenum chamber and improves the resonance charge effect. The result is an amplification of pressure waves within each half of the manifold at lower engine speeds, improving low rpm torque. The open ends of the intake runners are also flared into a "trumpet" shape (as on racing engines) to further improve airflow.

At higher engine speeds (3,950 rpm with the 3.5-liter, and 4,000 rpm with the 3.7-liter) the butterfly valves open, connecting the two halves of the manifold to increase its effective volume. The inertia of this increased air mass forces more charge into each cylinder for better cylinder filling, increasing torque at high rpm. The manifold's two modes further complement the changes in low and high speed running made possible by the VTEC® system. Both the 3.5-liter and 3.7-liter intake manifolds are fitted with a specially-cast top plate featuring a machined Acura logo.

DIRECT IGNITION AND DETONATION-KNOCK CONTROL

Because accurate spark timing is crucial for best power and torque output as well as reduced emissions, the Powertrain Control Module (PCM) continually monitors several engine parameters to determine optimum spark timing in all conditions. Additionally, a block-mounted acoustic detonation (knock) sensor "listens" to the engine, sending information about potentially damaging detonation to the PCM, which then retards ignition timing to help prevent damage. The ignition system is complemented by coil units positioned directly above each iridium alloy-tipped sparkplug, which require no scheduled service prior to 100,000 miles of use.

HIGH-FLOW EXHAUST SYSTEM WITH CLOSE-COUPLED CATALYTIC CONVERTERS

The TL 3.5-liter and TL SH-AWD® 3.7-liter engines both have exhaust manifolds that are cast directly into the cylinder heads for reduced weight, parts count and bulk. Attached directly to the cylinder heads are high-efficiency catalytic converters. The 3.5-liter engine has 900-cell/in2 converters, while the 3.7-liter engine has 600-cell/in2 converters. Due to closer-than-normal proximity to the exhaust ports, the close-coupled catalytic converters "light off" very quickly after the engine starts, reducing emissions in the critical cold start-up mode. To ensure optimum flow and low backpressure, a hydroformed two-into-one collector connects the close-coupled catalytic converters to the main 350-cell under-floor catalytic converter.

Downstream of the under-floor catalytic converter, the 3.5L engine has a single exhaust pipe that splits to a pair of resonators, each fit with a high-performance muffler and rectangular exhaust tip.

The 3.7L SH-AWD® engine has a special high-flow exhaust system that splits just past the under-floor catalytic converter. To provide clearance for the all-wheel-drive rear-mounted differential, one exhaust pipe is routed on each side of the driveshaft and feeds into a high-flow muffler on each side of the vehicle. Dual exhaust outlets on each side (a total of four) give the TL SH-AWD® a unique appearance. In keeping with its performance character, the 3.7-liter SH-AWD® exhaust system is also tuned to have a sportier, more aggressive exhaust note above 3,000 rpm than does the 3.5-liter TL.

EMISSIONS CONTROL

Both the 3.5L and 3.7L V-6 engines have gained power and torque over their previous counterparts with no increase in emissions. Both engines meet EPA TIER 2 - BIN 5 and CARB LEV II ULEV emission standards, and both are certified to this stringent standard for 120,000 miles of service.

Contributing to this performance are close-coupled catalytic converters which light-off quickly on start-up, an increased amount of EGR gas recirculated into the engine and an advanced 32-bit RISC microprocessor within the Powertrain Control Module (PCM) that boosts computing power to improve the precision of fuel and spark delivery at all engine speeds and conditions. Particularly in the critical post-startup mode, the high-efficiency multi-hole fuel injectors help deliver better fuel atomization for lower emissions.

Both TL engines feature Programmed Fuel Injection (PGM-FI) that continually adjusts fuel delivery to achieve the best power, fuel efficiency and low emissions.

ONE-TOUCH STARTER SYSTEM WITH HIGH-POWERED STARTER

Both the 3.5L and 3.7L engines both feature a one-touch system that automatically maintains starter engagement until the engine has started. For both TL models, the driver simply activates the starter switch once (or pushes the START/STOP button if equipped with the Technology Package) and needs not hold the switch in the Start position. The system starts the engine and disengages the starter automatically.

NOISE, VIBRATION AND HARSHNESS (NVH) CONTROL

The TL is designed to effectively control Noise, Vibration and Harshness (NVH). Cylinders with 60-degree V-angles, high-rigidity die-cast engine blocks, strong forged-steel crankshafts, stiff cast aluminum engine oil pans and die-cast accessory mounts team to reduce engine NVH. The intake and exhaust systems have been designed to emit a refined and quiet tone at low speeds, with a sporty exhaust note above 3,000 rpm.

Electronically Controlled Mounts at the front and rear of the transversely oriented engine block have two firmness settings. At low speeds the engine mounts are softer and the mount firmness increases as engine speed rises.

100,000 MILE TUNE-UP INTERVAL

All TL models are engineered to be exceptionally low-maintenance automobiles. With features like iridium alloy-tipped spark plugs and a self-tensioning serpentine accessory drive belt, the engines require no scheduled maintenance until 100,000 miles of use— with the exception of periodic inspections and normal replacement of fluids and filters. The first scheduled service at 100,000 miles includes items such as valve adjustment, timing belt replacement and water-pump inspection. Exact mileage is determined by actual driving conditions.

ENGINE COMPARTMENT COVER

To provide a clean appearance while highlighting the engine, both the TL and TL SH-AWD® have a five-piece engine compartment cover that conceals accessory systems. The engine itself is visible, and is handsomely finished to eliminate the need for traditional cosmetic covers.

MAINTENANCE MINDER

The TL and TL SH-AWD® have as standard equipment a Maintenance Minder™ system to monitor operating conditions and to alert the driver should maintenance be required. When the ignition is first turned on, the Multi-Information Display (MID) located between the tachometer and speedometer shows maintenance information, if required. To avoid distraction, the display is not shown while driving. MID identifies the remaining percentage of engine oil life, and indicates (with a wrench icon) when service is due. A percentage-based countdown to the next service is displayed when the car is within 15-percent of the end of the service interval. The type of service required is shown in an alphanumeric code, and if a service is missed, the MID indicates its urgency by showing past-due mileage.

The owner-resettable Maintenance Minder™ system monitors the service life of normal service parts and systems including oil, oil filter, tire rotation, air cleaner, automatic transmission fluid, rear differential fluid (on SH-AWD® model), spark plugs, timing belt, and coolant. In addition, Maintenance Minder™ is designed to eliminate unnecessary maintenance, reduce environmental impact and expenses, and help ensure long component and vehicle life.

SEQUENTIAL SPORTSHIFT 5-SPEED AUTOMATIC TRANSMISSION

To maximize driver control, acceleration and fuel economy, both the TL and the TL SH-AWD® are equipped with a 5-speed automatic transmissions featuring Sequential SportShift with Grade Logic Control System and racing-inspired steering wheel mounted paddle shifters.

The TL's 5-speed automatic transmission now incorporates low-drag clutches for Second through Fifth gears and has a high torque capacity.

Similar to the 2010 RL, the transmission in the TL SH-AWD® has a more robust case, larger shafts, larger gear clutches with low-drag friction material, and a special torque converter (and lock-up assembly) that contribute to low maintenance and high durability. For improved reliability, an external transmission cooler is standard with the SH-AWD® model. The TL's transmission has the widest gear-ratio spread of any 5-speed automatic transmission in its class, providing good acceleration in lower gears and relaxed, fuel-efficient cruising in higher gears. There is no scheduled maintenance for the Sequential SportShift transmission until 120,000 miles of use.

The Sequential SportShift transmission is controlled by an intuitive straight-gate console-mounted shifter or by a steering wheel paddle shifter system that works in both Drive and Sport modes. Grade Logic Control is paired with precise shift programming to provide improved performance and crisper driving feel.

In Sport shift mode, the Sequential SportShift transmission delivers excellent performance as a result of special shift map programming. During upshifts, the transmission holds Third and Fourth gears longer into the engine's rpm range for improved acceleration. On downshifts, a racing-style "blip" of the throttle helps match transmission gear speeds for improved performance. In addition, transmission-fluid line pressure releases the previous gear exceptionally fast, and the next gear's clutch pack line pressure is applied aggressively for very quick engagement.

Automatic Mode
The Sequential SportShift transmission can be operated in a conventional fully automatic mode with the console-mounted straight-gate shifter. In automatic mode, the transmission incorporates an advanced Grade Logic Control System and Shift Hold Control, both of which reduce unnecessary shifting and gear hunting.

Shift Hold Control keeps the transmission in its current (lower) gear ratio when the throttle is quickly released and the brakes are applied, as in the case of decelerating on corner entry. Such shift hold control leaves the chassis undisturbed by excess shifting and ensures that power will be immediately available (without a downshift) on corner exit.

While traveling up or down hills, Grade Logic Control alters the transmission's shift schedule to reduce shift frequency and improve speed control. A shift map in the transmission computer continually measures throttle position, vehicle speed and acceleration/deceleration, and then determines when the car is on a hill. The shift schedule is then adjusted to hold the transmission in lower gears to boost climbing power or to provide engine braking when traveling downhill.

Regardless if the shifter is in Sport or Drive mode, the use of the steering-wheel-mounted paddle shifters is permitted. However, when operated in Drive, the transmission returns to its normal fully automatic Drive mode if further paddle shift inputs are not made within a short time.

Sport Mode
By moving the center console mounted selector lever rearward to a detent labeled "S," the transmission is shifted into Sport mode, where the transmission operates exclusively via racing-inspired paddle shifters mounted on the steering wheel. When in Sport mode, a digital display on the tachometer face indicates which gear the transmission is in. Heightening driver control and involvement, dedicated shift logic in Sport mode delivers quicker shifts than in fully automatic mode.

To prevent damage to the powertrain when the transmission is in Sport mode, special features in transmission and engine programming alter shift logic in Second, Third and Fourth gears. The Powertrain Control Module (PCM) can also cut off engine fuel flow to help prevent over-revving.

If fuel cut-off alone is insufficient to prevent engine over-revving (as when the vehicle is on a steep downhill) the transmission will automatically upshift to prevent damage. On downshifts, the transmission will not execute a driver command that will over-rev the engine. For improved stop-and-go performance, even though the transmission has been left in a higher gear, the Sequential SportShift transmission will automatically downshift to First gear as the vehicle comes to a stop— thus preventing "lugging" the engine.

COOPERATION BETWEEN TRANSMISSION AND DRIVE-BY-WIRE™ THROTTLE SYSTEM

Shift speed and smoothness are enhanced as a result of cooperation between the Drive-by-Wire™ throttle system and the electronically controlled Sequential SportShift transmission. During upshifts and downshifts, the engine can be throttled by the engine management system, reducing peak forces (shift shock) on transmission components, thus improving component reliability and decreasing driveline harshness.

STRAIGHT-GATE SHIFTER ASSEMBLY

The straight-gate shifter located in the center console is intuitive and easy-to-use. The shifter allows the driver to choose D (enabling the use of First through Fifth gears) or D3 that limits transmission gear selection to First through Third gears. Placing the shifter in the "S" detent activates the Sport mode and only allows gear selection via the racing-inspired paddle shifters mounted on the steering wheel.

CLOSE RATIO 6-SPEED MANUAL TRANSMISSION

The availability of a 6-speed manual transmission for the 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 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 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 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 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 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 stress risers. First gear synchronizers are a triple cone design, Third and Fourth gear synchronizers feature 5.9-percent higher torque capacity, Fifth and Sixth gear synchronizers feature 9.1-percent higher torque capacity and the gearbox delivers a much improved shifting feel.

The 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.

Transmission Gearing Comparison
  TL 6-speed Manual TL 5-speed Automatic 2008 TL Type-S

First gear

13.928 :1 12.225:1 12.920 :1

Second gear

8.607 :1 7.280:1 8.140 :1

Third gear

5.877 :1 4.855:1 5.585 :1

Fourth gear

4.323 :1 3.146:1 4.106 :1

Fifth gear

3.258 :1 2.226:1 3.203 :1

Sixth gear

2.637 :1 N/A 2.529 :1

Reverse gear

3.656:1 1.888:1 4.008:1

Final Drive

3.842:1 4.533:1 3.285:1

1st - 6th gear ratios are overall ratios and do not factor in tire diameter

 

HIGH PERFORMANCE CLUTCH

Acura engineers designed an entirely new clutch system for the new 6-speed manual transmission fit to the 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 competitor vehicles including top European sports sedans.

Employing a 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 engagement during the entire 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 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.

SUPER HANDLING ALL-WHEEL DRIVE™ (SH-AWD®)

The 3.7-liter TL SH-AWD® features Acura's Super Handling All-Wheel Drive™, which progressively distributes optimum torque not only between the front and rear axles but also between the left and right rear wheels. The benefits of the system are not only superior all-weather traction but neutral, accurate steering under power that is unmatched by front drive, rear drive or conventional all-wheel-drive systems.

By utilizing torque vectoring, SH-AWD® helps to turn the vehicle through the corner— thus helping reduce understeer and improving handling balance and controllability. With cornering forces more evenly distributed between front and rear tires, overall cornering ability is increased. Also, rather than using only the steering angle of the front tires to turn the vehicle, SH-AWD® can overdrive the speed of one rear wheel to create a "yaw moment" that reduces understeer.

Vehicles with high power ratings using conventional front or rear drive systems generally use a limited-slip differential to help maintain traction under power. By linking inside and outside drive wheels, these systems tend to resist turning and can increase understeer—working against the front tires as they attempt to turn the vehicle. Conventional AWD systems work similarly to link the inboard and outboard tires and the front and rear axles that can create resistance to turning. Using torque vectoring to help turn the vehicle, SH-AWD® creates a more responsive, neutral and predictable platform while retaining the usual benefits of all-wheel drive.

Electronic Controls and Parameters
The control logic for SH-AWD® is integrated with the TL's Vehicle Stability Assist™ (VSA®) ECU. The Powertrain Control Module (PCM) provides information on engine rpm, intake airflow and transmission gear selection, while the VSA® ECU provides wheel-speed data. The SH-AWD® ECU also monitors steering angle, lateral g-forces, yaw rate, and electromagnetic clutch engagement for the right and left rear axle shafts. Drive torque is calculated from PCM information, and then the acceleration situation, wheel spin, lateral g-forces and steering angle are used to determine the front-to-rear torque distribution and the torque split between right and left rear wheels.

SH-AWD® operating parameters include:

  • Up to 90-percent of available torque can be transferred to the front wheels during normal cruising.
  • In hard cornering and under acceleration, up to 70-percent of available torque can be directed to the rear wheels to enhance vehicle dynamics.
  • Up to 100-percent of the torque sent to the rear axle can be applied to either rear wheel.

SH-AWD® System Layout
The TL SH-AWD® is a full-time all-wheel-drive system that requires no driver interaction or monitoring. A torque-transfer unit is bolted directly to the front-mounted transaxle. The torque-transfer unit receives torque from a helical gear that is attached to the front differential's ring gear, and a short horizontal shaft and hypoid gear set within the torque-transfer unit's case send power to the rear propeller shaft, which in turn transfers power to the rear drive unit.

The TL SH-AWD® rear drive unit is constantly overdriven by 1.7-percent and the resulting overdrive effect is regulated by left and right side electromagnetic clutch packs which independently control the power delivered to each rear wheel.

Direct Electromagnetic Clutch Systems
Two direct electromagnetic clutch systems mounted on either side of the hypoid gear (that drives the rear axle) control the amount of torque sent to each rear wheel and provide a limited-slip differential function when needed. The clutches can be controlled as a pair to alter front/rear torque split or they can be controlled independently to allow 100-percent of rear axle torque to go to just one rear wheel.

An electromagnetic coil modulates the pressure controlling each clutch pack, which changes the speed of the sun gear within a planetary gearset thereby controlling the torque sent to the wheel. Electromagnetic control of the clutches permits torque delivery to each rear wheel to be proportioned in an exceptionally quick and precise manner, which helps reduce wheel-slip in low-traction conditions.

The clutch packs and their friction material are carefully designed to withstand the small amount of continuous slip between front and rear axles (created by the 1.7-percent speed differential) while delivering the durability expected of an Acura product. Through an oil-temperature sensor, the PCM monitors the clutch-plate coefficient of friction (which changes with temperature) in each clutch pack and then adjusts the voltage to each electromagnetic coil to compensate. As miles accumulate, the PCM uses data from a feedback loop to adjust the voltage supplied to the electromagnetic coils to compensate for any clutch wear, ensuring optimal and consistent transmission of torque.

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