2002 Acura 3.2 TL -- Powertrain

9/28/2001 11:22:26 PM

OVERVIEW
Two engines are offered in the 2002 TL. Propelling the 3.2TL is an all-aluminum, 3.2-liter V-6 that uses 24 valves and Acura's innovative VTEC system to deliver 225 horsepower and 216 lb-ft. of torque.

The V-6 in the high-performance TL Type-S model builds upon this potent foundation by adding a high-flow, dual-stage induction system and a free-flowing exhaust -- which help boost output to 260 horsepower and 232 lb-ft of torque.

In each engine, Acura's patented VTEC system -- first unveiled on the NSX exotic sports car -- helps provide an exceptionally flat torque curve, enhanced engine breathing, and superb responsiveness at all engine speeds.

Both the TL and the TL Type-S are equipped with an electronically controlled, 5-speed automatic transmission with Acura's Sequential SportShift system. Inspired by the transmissions used on modern Formula One race cars, Sequential SportShift allows the driver to shift the forward gears semi-manually -- without the need for a clutch pedal. The transmission also offers the shifting convenience of a conventional automatic.

 In keeping with Acura's commitment to the environment, both TL engines meet stringent Low Emission Vehicle (LEV) standards. The California-model 3.2 TL also meets Ultra Low Emission Vehicle (ULEV) requirements.

Powertrain at a Glance

Engine

  • 3.2 liter, SOHC, V-6, aluminum alloy engine
  • 225 hp at 5600 rpm and 216 lb.-ft. of torque at 4700 rpm (TL)
  • 260 hp at 6100 rpm and 232 lb.-ft. of torque between 3500 and 5500 rpm (TL Type-S)
  • Variable Valve Timing and Lift Electronic Control (VTEC)
  • Dual-stage induction system and high-flow exhaust (TL Type-S)
  • Computer-controlled Programmed Fuel Injection (PGM-FI)
  • Direct ignition system
  • 105,000-mile tune-up intervals

5-Speed Automatic Transmission

  • Quick-response, 5-speed Sequential SportShift allows semi-manual operation
  • Wide-ratio, 5-speed design helps improve performance and fuel economy
  • Direct-control, automatic transmission managed by Powertrain Control Module (PCM) for enhanced shifting smoothness
  • Grade Logic Control for reduced gear "hunting" when driving in hilly country

Emissions/Fuel Economy

  • 3.2 TL/Type-S EPA fuel economy of 19/29 mpg (city/highway)
  • 3.2 TL and Type-S meet LEV standards; California-edition 3.2 TL meets ULEV standards
  • Electronically controlled Exhaust Gas Recirculation (EGR)

Noise, Vibration, and Harshness (NVH)

  • Smooth-running, 60-degree V-angle engine design
  • Full-floating piston pins eliminate piston slap during warm-up
  • Elimination of separate camshaft holders allows for a more compact, rigid cylinder head
  • Lightweight pistons and connecting rods
  • Three hydraulic engine mounts
  • Cast-aluminum oil pan
  • High-rigidity cylinder block with additional strengthening ribs for the TL Type-S

ENGINE ARCHITECTURE
Under the hood of the '02 TL lies a sophisticated, 24-valve, 3.2-liter V-6 engine. In addition to its lightweight, all-aluminum construction and compact, smooth-firing, 60-degree layout, the engine incorporates such state-of-the-art technologies as the VTEC system and a high-flow induction system to combine prodigious power with smooth, refined operation. In addition, the high-performance Type-S V-6 uses a unique, dual-stage induction system to boost output to 260 horsepower.

ENGINE BLOCK
The compact, aluminum engine block of the TL V-6 is die-cast and heat-treated for exceptional rigidity and minimal resonant vibration. The engine's iron cylinder liners have their bore pitch set at a close 98-mm spacing to reduce overall engine size. The TL V-6 is narrower than competing engines from Lexus and Infiniti. The free-revving TL engine is oversquare with a bore of 89 mm and a stroke of 86 mm -- yielding a total displacement of 3210 cc.

The TL employs an engine cylinder bank V-angle of 60 degrees for improved smoothness and compactness. The block has an unusually short deck height, resulting in an overall reduction in the height and width of the assembled engine.

The Type-S engine adds separate, spin-cast cylinder-wall liners that are cast into the engine block during the initial manufacturing phase. These spin-cast liners provide additional weight reduction over traditional iron liners -- and also provide added heat rejection to avoid engine knocking. Because they require fewer machined surfaces, spin-cast cylinder liners also simplify the production process.

CYLINDER HEAD
The powerful TL engines incorporate pressure-cast, aluminum alloy cylinder heads with four valves per cylinder, compact combustion chambers, and a generous squish area. For enhanced flow into the combustion chamber, the Type-S engine has specially designed, race-bred intake valves. The single overhead camshaft in each cylinder head is installed from the timing belt side of the engine, saving weight and complexity by eliminating the need for bolt-on cam caps. The cams are driven by the crankshaft via a fiberglass-reinforced, toothed timing belt and use friction-reducing roller followers to activate the valves.

CRANKSHAFT/CONNECTING RODS/PISTONS
Of paramount importance in designing the TL's V-6 was the goal of compact overall engine dimensions. Thus, the TL engine uses a rigid, forged crankshaft and narrow 19 mm connecting rods to reduce engine length and width. Rather than conventional nut-and-bolt type fasteners, the connecting rods in the TL V-6 use lighter bolts (without nuts) called plastic-region fasteners. These allow the rod bolts to be smaller while retaining the required clamping force and strength margins.

The V-6's compact pistons are made of lightweight, cast-aluminum alloy. A unique dome-shaped design provides maximum combustion efficiency in each combustion chamber. The compression ratio is 9.8:1 in the 3.2 TL and 10.5:1 in the Type-S due to a taller piston dome. The pistons themselves feature a 3-ring design; to accommodate the higher combustion pressure. The Type-S engine uses a specially angled top ring for an improved seal within the cylinder.

VARIABLE VALVE TIMING AND LIFT ELECTRONIC CONTROL (VTEC)
First unveiled on the Acura NSX supercar, the innovative Variable Valve Timing and Lift Electronic Control (VTEC) system is a key player in the TL engine's remarkable combination of high-power and impressive fuel efficiency.

Unlike engines with conventional fixed-timing intake valves, the TL's VTEC engines automatically optimize themselves according to engine speed. By altering the lift and opening duration of the intake valves depending on engine rpm, VTEC helps the engine produce abundant low- and mid-range torque with no sacrifice in high-rpm power. Indeed, at high rpm the VTEC V-6 produces considerably more horsepower than other engines of its size.

At low rpm, the VTEC intake valves follow a set of low-lift, short-duration cam lobes with timing that optimizes cylinder filling. In addition, the timing of the intake valves is staggered and their lift asymmetric -- creating a swirl effect within the combustion chambers at lower RPM. The result is increased burn speed with improved combustion stability and an increase in allowable EGR rate. As the engine spins through 4400 rpm (4800 rpm on the Type-S), the intake rocker arms transition to actuation by high-lift, long-duration cam lobes designed to optimize high-rpm output.

On the Type-S, high-performance camshafts further increase power output by providing longer intake-valve duration, more valve overlap, and additional lift for the exhaust valves.

DUAL-STAGE INDUCTION SYSTEM
Found only on the Type-S engine, this revolutionary induction system is a major contributor to the V-6's class-leading 260 horsepower. At its heart, the system uses a large, two-chamber intake plenum separated by a valve, which opens at 3800 rpm and is powered by an electric motor.

At low and mid-range engine speeds, the valve is closed -- creating a Resonance Charge condition where pressure pulsations between cylinders banks are separated. In doing so, air filling the cylinders increases with the resonance energy from the adjoining cylinder of each bank (Helmholtz principle).

At mid to high engine rpm, the valve opens and an Inertia Charge condition is achieved. Increased air filling then occurs when the manifold volume (plenum) is increased and the resonance charge condition is eliminated. This phenomenon utilizes the high flow mass to pressurize the manifold port air, producing a natural "supercharger" effect.

The increased airflow and improved cylinder filling is the fundamental reason for the engine's efficient combustion and subsequent power. Additional improvements include a larger 64-mm bore throttle body (which reduces air-intake restriction and increases total air flow volume), free flow exhaust, and a low-overall restriction air intake system with a free flow air filter and air flow tube.

PROGRAMMED FUEL INJECTION (PGM-FI)
A Programmed Fuel Injection (PGM-FI) system controlled by a 16-bit, 32 MHz Powertrain Control Module (PCM) monitors many variables including throttle position, engine temperature, intake manifold pressure, atmospheric pressure, exhaust gas oxygen content, and intake air temperature. The (PGM-FI) system controls fuel delivery by six injectors mounted in the cast aluminum, tuned-length intake manifold. While tracking the operation of the engine with position sensors on the crankshaft and both camshafts, the PCM also controls the 5-speed Sequential SportShift automatic transmission when it operates in automatic mode.

EXHAUST SYSTEM
The lightweight, high-flow, dual-exhaust system in the 2002 TL is designed for low-restriction performance with minimal noise and vibration. The high-output Type-S engine has a larger-diameter exhaust pipe, an increased-flow catalytic converter, and ultra-high-flow capacity dual mufflers. The result is a 30 percent increase in exhaust gas flow compared with the 3.2 TL. The Type-S also boasts an aggressive, performance-oriented exhaust note that settles into a subdued tone at cruising speeds.

DIRECT IGNITION SYSTEM/KNOCK CONTROL
While proper ignition timing is critical to optimized engine performance and emission control, proper timing depends on many variables and constantly changes from moment to moment. If there is not enough spark advance, fuel efficiency suffers. If there is too much advance, engine knock or even engine damage may occur. The TL is equipped with a new-generation knock-control system. Using a centrally located engine-block sensor that "hears" the onset of knocking, the system can advance ignition timing to the point of peak efficiency -- without going beyond. The system is even able to adapt if the quality of fuel used is less than the specified unleaded premium.

The ignition system further benefits from compact and reliable direct-ignition coil units, which are positioned directly in the spark plug access bores.

NOISE, VIBRATION, AND HARSHNESS (NVH) CONTROL
In addition to power and fuel efficiency, the TL powertrain was engineered for superb smoothness and noise control. To that end, the TL's V-6 engines incorporate such NVH-reducing features as a rigid aluminum block with an unusually high resonant frequency, a rigid forged crankshaft, die-cast accessory mounts, and a stiff, cast-aluminum oil pan.

105,000-MILE TUNE-UP INTERVALS
For the first 105,000 miles, the TL engines require only routine inspections and fluid and filter changes. Thanks to the roller-follower design of the VTEC valvetrain, friction and wear are reduced to the point that the screw-type tappet clearance adjusters need not be checked until the 105,000-mile mark. At that point, the long-life, platinum-tipped spark plugs are also scheduled for replacement.

DIRECT-ACTING CRUISE CONTROL
For relaxed highway cruising, the TL is equipped with a sophisticated electronic cruise-control system. When engaged, the system's Powertrain Control Module (PCM) is able to command the 5-speed transmission directly, summoning downshifts as required to help maintain the driver's preset road speed even when climbing steep grades. For added convenience, the cruise control can be operated using buttons on the steering wheel. Using these buttons, the driver can adjust road speed in one mph increments or disengage the cruise-control system without touching the brake pedal.

5-SPEED, SEQUENTIAL SPORTSHIFT' AUTOMATIC TRANSMISSION
Though advances in usable engine power output play a significant role in the TL's quick acceleration, its 5-speed automatic transmission figures heavily in measured performance gains and performance driving feel. Its gear ratio settings closely match the demands of a variety of driving situations. The wide ratio transmission's lower gears provide quick acceleration while the tall top gear ratio results in low cruising rpm's for reduced engine noise and lower fuel consumption.

Thanks to a design that shares the idler and third-gear clutches, the TL's transmission provides five ratios in a unit about the size of a conventional 4-speed transmission. The transmission also incorporates a first gear one-way clutch for smoother shifts, plus a heat exchanger design that moderates transmission operating temperature quickly and without undue complexity.

Linear solenoids provide precise, real-time control of the clutch on/off pressure in the TL's transmission. Thanks to this superior clutch-engagement accuracy, the control logic system operates smoothly under all conditions. For added refinement, a bearing supports the idler shaft.

To manage overall powertrain operation, the PCM interacts with multiple safety and control strategies. For instance, by limiting engine output torque and/or transmission clutch pressure, harsh driveline shocks are eliminated. The system also prevents the engine from exceeding 5000 rpm when the transmission is in neutral or park.

The TL boasts 5-speed automatic transmission with an advanced Sequential SportShift feature as standard equipment. Similar to the transmissions found on contemporary Formula One Grand Prix race cars, Sequential SportShift allows the driver to choose the convenience of a conventional automatic or shift gears semi-manually. To do the latter, the driver places the gear lever in a special SportShift gate to the left of "Drive," and then simply moves the lever fore or aft to shift up or down. A clutch pedal is not needed. The selected gear is displayed on an LED indicator inside the tachometer face.

To improve the immediacy and "manual-transmission feel" of the shifting experience in SportShift mode, the transmission computer commands shifts that are firmer and approximately 10 percent quicker than those in automatic mode. At the same time, the SportShift system incorporates built-in safety-override features unavailable with a conventional manual transmission. For instance, the transmission logic will not allow a downshift that would cause the engine to over-rev.

GRADE LOGIC CONTROL
To improve powertrain smoothness and reduce gear "hunting" on steep grades, the 5-speed automatic transmission is equipped with a standard Grade Logic Control system. Using sensors that monitor throttle position, vehicle speed, and acceleration/deceleration the system compares these inputs with a map stored in the transmission computer, determines when the vehicle is on an incline and adjusts the shift schedule for improved climbing power or downhill engine braking.