2009 Acura TL - Powertrain

POWERTRAIN OVERVIEW

The 2009 Acura TL and TL SH-AWD® are each fitted with a transversely mounted V-6 powertrain that has been painstakingly 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 all intake valves actuated by the Acura VTEC® (Variable Valve Timing and Lift Electronic Control®) system. This compact and efficient engine produces 280 horsepower and 254 lbs-ft of torque. Compared to the previous generation TL's 3.2-liter engine, the 3.5-liter V-6 delivers 22 additional horsepower and 21 additional lbs-ft of torque.

The TL SH-AWD® is powered by a new 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. Compared to the previous generation TL Type-S 3.5-liter engine, the 2009 TL's 3.7-liter V-6 has gained 19 horsepower and 17 lbs-ft of torque. Similar to the 3.7-liter engine that now powers the 2009 RL sedan, the new TL SH-AWD® engine features a new VTEC® system which varies the exhaust valves as well as the intakes to contribute to elevated power output. The engine is even lighter than the 3.5-liter powerplant it replaces, due in part to the use of aluminum rather than iron cylinder liners.

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

The transmission in all versions is a new Sequential SportShift 5-speed automatic transmission with a new straight-gate style console-mounted shifter. For more spirited driving, a new "smart" F1-style steering wheel paddle shifter system is standard and now works when the transmission is in "Drive" rather than only in "Manual" mode as in the past. Grade Logic Control and revised shift programming refine driving feel and improve performance.

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 joins the TL lineup. The 2009 TL SH-AWD® features Super Handling All-Wheel Drive™, Acura's advanced drivetrain system that delivers quick, precise all-wheel-drive response. SH-AWD® made its debut on the 2005 RL, and at its introduction it was 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 direct yaw control feature makes the 2009 TL SH-AWD® exceptionally neutral under power, for greater handling precision and control.


2009 TL
2009 TL SH-AWD®
Engine
SOHC VTEC®
(intake) V-6
SOHC VTEC®
(intake and exhaust) V-6
Displacement
3.5-liter (3471 cc)
3.7-liter (3664 cc)
Compression ratio
11.2:1
11.2:1
Fuel type
Premium Unleaded,
91 octane
Premium Unleaded,
91 octane
Horsepower @ rpm
280 @ 6,200
305 @ 6,200
Torque @ rpm (lbs-ft)
254 @ 5,000
273 @ 5,000
Transmission
5 AT
5 AT
EPA estimated mileage
(city/highway)
18/26*
17/25*
Emissions certification
EPA TIER 2 - BIN 5
and CARB LEV II ULEV
EPA TIER 2 - BIN 5
and CARB LEV II ULEV

*Based on 2009 EPA mileage estimates, reflecting new EPA fuel economy methods beginning with 2008 models. 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
  • 3.5-liter SOHC V-6 aluminum alloy 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®) on intake valves
  • Dual-Stage induction system with lightweight magnesium intake manifold
  • 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®

  • SH-AWD® drivetrain for performance handling and all-season capability
  • 3.7-liter SOHC V-6 aluminum alloy engine
  • 305 hp at 6,700 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®) on both intake and exhaust valves
  • Dual-stage induction system with lightweight magnesium intake manifold
  • Cold-air intake system
  • Larger throttle-body (69 mm diameter versus 64 mm) for the Drive-by-Wire™ throttle system
  • Integrated exhaust manifolds cast directly into the cylinder heads
  • High-flow, sport-tuned dual exhaust system with four 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 (both 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 mpg* (city/highway)

TL SH-AWD®

  • EPA estimated 17/25/20 mpg* (city/highway/combined)

*Based on 2009 EPA mileage estimates, reflecting new EPA fuel economy methods beginning with 2008 models. 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 with paddle shifters and grade logic control

  • Quick-response Sequential SportShift allows semi-manual operation
  • New straight-gate style console-mounted shifter
  • Steering-wheel mounted F1®-style paddle shifters
  • Paddle shifters functional in Drive and Sport modes
  • Coordination between Drive-by-Wire™ throttle system and 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

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 grip 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 unique 2-rocker VTEC® variable valve timing system, with variable lift for the intake valves. Power is enhanced with an 11.2:1 compression ratio, high-output port shapes, intake airflow enhancements, and a sport-tuned exhaust system. While torque numbers are equivalent to the 3.5L in the outgoing Type-S, when compared to the previous 3.2L engine, the 3.5L produces 9- to 13-percent more torque between 2,000 and 4,000 rpm-the engine speed most commonly used in day-to-day driving. In addition to a high specific power output, the 3.5-liter V-6 delivers exceptional refinement and low emissions.

The 3.7-liter engine in the TL SH-AWD® is an enhanced version of the powerplant in the 2009 Acura RL, and it 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® variable valve timing system features variable lift and timing for both intake and exhaust valves. Increases in intake airflow and compression ratio, combined with a high-flow exhaust system using close-coupled catalytic converters and dual exhaust pipes with four exits, help make the TL SH-AWD® engine the most powerful engine that Acura has ever offered.

ENGINE BLOCK

Both the 3.5-liter TL engine block and that of the 3.7-liter TL SH-AWD® are constructed of lightweight die-cast aluminum. The 3.5-liter engine has thin-wall iron 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 an effective bond with the aluminum block, enhancing block stiffness and heat transfer from the liners to the block.

The 3.7-liter TL SH-AWD® 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 SH-AWD® engine to have larger cylinder bores, even though its bore-center dimensions (the distance between the centers of adjacent bores) remain unchanged.

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 uniquely integrated exhaust-port castings that provide optimal positioning for close-coupled catalytic converters, one on each cylinder bank. This design results in more rapid "light off" of the catalytic converters on 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 belt drive for long service life. Compared to the camshafts used in the 2009 MDX's 3.7L V-6, the 2009 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. Compared to the camshafts in the 2009 RL's 3.7L V-6, valve timing has been optimized for the TL's exclusive 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 over earlier designs. Compared to the earlier 3.5-liter, 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 strong low-speed torque, crisp throttle response, 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, these 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 superior power at peak rpm.

The 3.7-liter engine in the TL SH-AWD® features a further refined version of the Acura VTEC® system, which made its sedan debut on the 2009 RL. 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 big 3.7-liter engine has the same VTEC® intake valve control system as the 3.5-liter engine, but adds a unique new 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 the revs rise, pressurized oil (controlled by the PCM) activates small pistons that locks 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-speed 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 new VTEC® system provides more power and torque, improved emissions and better fuel economy. Plus, the new VTEC® hardware offers greater durability and features roller cam followers to decrease frictional losses.

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 3.5- and 3.7-liter engines use different drive-by-wire throttle 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, and 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, the system is programmed to "blip" the throttle to help match engine speed to gear speed within the Sequential SportShift automatic transmission.

COLD AIR INDUCTION SYSTEM

The TL and TL SH-AWD® use new design cold air induction systems that pull 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 air in the engine compartment. Cool air is denser and contains more oxygen per volume than warmer air, allowing the engine to make more power. Carefully designed ducting routes fresh air to the air cleaner assembly and then to the throttle-body. The 3.5-liter engine has a 64 mm diameter throttle-body, while the 3.7-liter engine uses a new 69 mm diameter throttle-body for 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 intake manifold spray directly toward the intake ports. The multi-hole injector design means that fuel droplet size is reduced for better fuel atomization, resulting in improved cold weather start-up, better fuel economy and higher horsepower.

2-PIECE DUAL-STAGE INTAKE MANIFOLD

Both TL models feature a dual-stage intake manifold made from lightweight magnesium. The manifold works together 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 valves are closed at low engine speed, which reduces the operating volume of the plenum and increases the effective length of the inlet passages. The result is maximum resonance effect and amplification of pressure waves within each half of the manifold at lower engine speeds, significantly increasing cylinder filling and thus 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, increasing its effective volume and increasing the mass of air rushing down each intake passage. 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 incrementally 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 more free-flowing 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 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 converter, the 3.5-liter engine has a single pipe that splits to a pair of resonators, each with a final high-performance muffler and rectangular exhaust tip. Exhaust flow has been increased by 1.5-percent compared to the previous TL 3.2-liter engine.

The 3.7-liter 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 TL. Dual outlets on each side (a total of four) give the TL SH-AWD® a unique appearance. The SH-AWD® system has a substantial increase in flow of 17-percent versus the previous TL Type-S system. In keeping with its performance character, the 3.7-liter SH-AWD® 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 TL 3.5-liter engine and the TL SH-AWD® 3.7-liter engine have gained power and torque over their previous counterparts with no increase in emissions. Both meet stringent EPA TIER 2 - BIN 5 and CARB LEV II ULEV emission standards, and are certified to this standard for 120,000 miles of service.

Acura's advanced technologies contributing to this performance are the 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 deliver better fuel atomization for lower emissions.

Both 2009 TL engines feature Programmed Fuel Injection (PGM-FI) that continually adjusts fuel delivery to achieve the best combination of power, fuel mileage, and low emissions.

ONE-TOUCH STARTER SYSTEM WITH HIGH-POWERED STARTER

The TL 3.5-liter and TL SH-AWD® 3.7-liter engines both feature a new starter with 18-percent more power to crank the engine. In addition, they features 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 it is 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 and TL SH-AWD® powertrains are 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, die-cast accessory mounts and stiff cast aluminum engine oil pans, low engine NVH is ensured. The induction and exhaust systems have been designed to emit a refined and quiet tone at low speeds, with a sporty "growl" above 3,000 rpm.

Electronically Controlled Mounts (ECM) at the front and rear of the transversely oriented engine block have two firmness settings that are softer at low speeds and firmer as engine speed rises.

100,000 MILE TUNE-UP INTERVAL

All TL models are exceptionally low-maintenance automobiles. With features like Iridium alloy-tipped spark plugs and the space-saving, self-tensioning serpentine accessory drive belt, these engines require no scheduled maintenance until 100,000 miles, exclusive of periodic inspections and normal replacement of fluids and filters. The first scheduled service at 100,000 miles includes valve adjustment, timing belt replacement, and water-pump inspection. Note that 100,000-mile tune-up interval does not apply to fluid and filter changes. 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 integrated five-piece engine compartment covers that conceal accessory systems. The engine itself is visible, and is handsomely finished to eliminate the need for cosmetic covers.

MAINTENANCE MINDER™

The TL and TL SH-AWD® have Maintenance Minder™ systems 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 driver distraction, the display is not shown while driving. MID indicates the remaining percentage of engine oil life, and indicates when service is due with a "wrench" icon. 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 system monitors all 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, coolant and is designed to eliminate unnecessary maintenance, reduce environmental impact and expenses, and 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 F1®-style steering wheel mounted paddle shifters and Grade Logic Control.

The TL's 5-speed automatic transmission now incorporates new low-drag clutches in Second through Fifth gears and has increased torque capacity.

Similar to the 2009 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 new torque converter and lock-up assembly that contribute to low maintenance and high durability. An external transmission cooler is standard with SH-AWD®. There is no scheduled maintenance for the transmission until 120,000 miles. The Acura transmission has the widest gear-ratio spread of any 5-speed transmission in the class, providing strong acceleration in lower gears and relaxed, fuel-efficient cruising.

Both transmissions are controlled by the new straight-gate console-mounted shifter or by a new "smart" steering wheel paddle shifter system that now works whenever the transmission is in Drive. Formerly, the paddles on the TL Type-S worked only in the Manual mode. Grade Logic Control is paired with revised shift programming to provide improved performance and crisper driving feel.

In Manual shift mode, both transmissions deliver improved performance as a result of revised shift map programming. During upshifts, the transmissions hold Third and Fourth gears longer into the engine's rpm range for improved acceleration. On downshifts, new shift logic generates up to 24-percent quicker response, with a racing-style "blip" of the throttle to help match gear speeds. Transmission-fluid line pressure releases the previous gear more quickly, and the next gear's clutch pack line pressure is applied more aggressively for quicker engagement.

Automatic Mode

The Sequential SportShift transmissions in both the TL and TL SH-AWD® can be operated in a conventional fully automatic mode with the new 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.

Whether in Sport or Drive, new "smart" logic programming allows the use of the steering-wheel-mounted paddle shifters. 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.

Manual 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 F1®-style paddle shifters mounted on the steering wheel. A digital display in 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 prevent over-revving.

If fuel cutoff alone is insufficient to prevent 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 and to prevent "lugging" the engine, the new Sequential SportShift transmission will automatically downshift to First gear even though the transmission has been left in a higher gear as the vehicle comes to a stop, to prevent "lugging" the engine.

STRAIGHT-GATE SHIFTER ASSEMBLY

The new straight-gate shifter, located in the center console, is a more intuitive, easy-to-use design and takes up less console space. The shifter allows the driver to choose D, using First through Fifth gears, or D3, which activates the Sport mode and allows gear selection via F1®-style paddle shifters mounted on the steering wheel.

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.

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. The 2009 Acura TL SH-AWD® system is similar to the systems used in the RDX and MDX SUVs.

By utilizing torque vectoring, and by rotating the outside rear wheel faster than the front axle speed while cornering, SH-AWD® helps to turn the vehicle through the corner-thus reducing understeer and improving handling balance and controllability. With cornering forces more evenly distributed between front and rear tires, overall cornering grip is increased. Also, instead of using only the steering angle of the front tires to turn the vehicle, the TL SH-AWD® adds additional torque through the outside rear tire 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 maintain traction under power. By linking inside and outside drive wheels, these systems tend to resist turning and to increase understeer-working against the front tires as they attempt to turn the vehicle. Conventional AWD systems similarly work to link the inboard and outboard tires and the front and rear axles and also 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, airflow, and transmission gear-ratio 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 Powertrain Control Module (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, depending on conditions.

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 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 gear set and controls 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 reduces 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 Powertrain Control Module (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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