2000 Acura 3.2 TL -- Powertrain
3/21/2000 11:20:50 PM
A single, potent powertrain drives the 3.2TL. To meet tougher emissions standards while simultaneously improving performance for 2000, this sophisticated all-aluminum V-6 now has revised camshafts, larger intake and exhaust valves, modified cylinder head porting, as well as a newly designed tuned-length intake manifold. These changes combine to broaden the 3.2TL's usable powerband and improve midrange torque, while making compliance with tough LEV and ULEV (for California models) standards possible.
The 3.2-liter VTEC-equipped engine is compact, lightweight and fuel-efficient, representing the next generation of Acura V-6 powerplants. The 60-degree, 24-valve V-6 is mounted transversely in the chassis, improving packaging efficiency. For 2000, it is coupled with a new 5-speed Sequential SportShift automatic transmission with Grade Logic Control that drives the front wheels with the assistance of a standard Traction Control System (TCS).
New 5-speed automatic transmission
- Quick-response 5-speed Sequential SportShift allows semi-manual operation
- Lockup torque converter operation increased to improve performance and efficiency
- 5-speed design helps improve acceleration and fuel economy
- New for 2000 simplified heat exchanger design stabilizes transmission operating temperature and improves fuel economy.
- Direct-control automatic transmission is managed by the Powertrain Control Module (PCM) for smoother shifting
- Grade Logic Control provides "smart" shift scheduling while driving through hills
- Smoother Cruise Control operation and reduced shift shock through Cruise Control ECU control of downshifting
- 225 horsepower at 5,600 rpm (peak up 100 rpm from 1999 TL engine)
- For 2000, mid-range torque is increased by 5.5 percent at 2500-4000 rpm
- VTEC cylinder heads with roller cam-follower rocker arms
- For 2000, acceleration from 0-60 mph is 0.5 seconds quicker
- Improved EPA fuel economy 19/29 mpg (city/hwy), up from 19/27 mpg in 1999
- All 2000 3.2TLs now meet LEV standards; California models meet ULEV standards
- Electronically controlled Exhaust Gas Recirculation (EGR)
- Improved engine startability system
- Variable Valve Timing and Lift Electronic Control (VTEC)
Noise Vibration and Harshness (NVH)
- Smooth running 60-degree V-angle
- 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
- Transmission gear noise improvement through tighter gear-teeth-mesh contact ratio
The TL is powered by a new-generation 3.2-liter, 225-hp, 24-valve V-6 engine. Remarkably compact and lightweight, the TL power plant and transmission incorporate a wide variety of advanced technologies. Relative to the previous-generation 1998 TL, total powertrain weight has been reduced by 16 percent. The engine alone accounts for eight percent of that weight reduction, no small feat in light of the engine's improved power output, refined NVH characteristics and high fuel economy.
Die-cast and heat-treated, the compact aluminum block is extremely rigid, with a high natural frequency and minimal resonant vibration. The TL V-6's iron cylinder liners have their bore pitch set at a close 98-mm spacing to reduce overall engine size. The free-revving TL engine is oversquare with a bore of 89 mm and a stroke of 86 mm to give the engine a total displacement of 3210 cc. The TL engine's V-angle is 60-degrees &endash; a departure from the 90-degree V-angle used in the previous-generation TL. This narrower angle improves smoothness and reduces overall bulk and weight. Designed to work with special compact pistons, the block has an unusually short deck height, resulting in an overall reduction in the height and width of the assembled engine.
The pursuit of compact overall engine dimensions coupled with Acura's high durability standards drove the design of the TL crankshaft and connecting rods. A rigid, forged crankshaft and narrow 19 mm connecting rods allow for a reduction in overall engine length, and are a contributing factor in making the TL powerplant (as installed in the car) narrower than its competition from Lexus or Infiniti, even though it offers more displacement and torque. The TL's rods don't use conventional nut-and-bolt type fasteners, but instead employ lighter bolts (without nuts) called plastic-region fasteners. These bolts are designed to operate in the plastic, not elastic, region of the steel material, unlike conventional fasteners. This allows a downsizing of the rod bolts while maintaining the proper clamping force and strength margins.
CYLINDER HEAD/LOW-FRICTION VTEC VALVE TRAIN
Though the new-generation TL's power characteristics were well received in '99, the car returns for 2000 with 1.0 mm larger intake and exhaust valves, modified cylinder head ports, revised camshafts and a new intake manifold design to deliver significant improvements in mid-range torque, and further broaden the TL's usable powerband.
The TL's 216 ft-lb torque peak is unchanged, but is now achieved at 4700 rpm (300 rpm lower than the '99 model). Meanwhile horsepower holds steady at 225, but the peak hits at 5600 rpm, up 100 rpm from '99. This broader spread between peak torque and peak horsepower makes strong acceleration more accessible in varied driving conditions. More importantly, the TL's new induction system and modified camshafts provides a significant boost in torque output at mid rpm. At 2500 rpm, for example, torque output is up by 11 foot-pounds-an increase of 5.5 percent.
With four-valve combustion chambers and a 9.8:1 compression ratio, the TL pressure-cast aluminum alloy cylinder heads reflect Acura's latest thinking in engine design. The single camshaft in each cylinder head is installed from the side, eliminating the need for bolt-on cam caps-a savings of weight and complexity. Driven by the crankshaft via a glass-fiber reinforced toothed belt, the cams actuate the valves via friction reducing roller followers.
The Variable Valve Timing and Lift Electronic Control (VTEC) valve train is a major contributing factor to the TL's remarkable combination of high power delivery and fuel economy. With the lift and opening duration of the larger intake valves altered automatically based on engine rpm, the engine develops strong low-speed torque without sacrificing high rpm power.
Conventional fixed intake valve timing can't equal this broad-range flexibility. The VTEC-equipped 2000 TL engine delivers the power expected of an engine its size at middle engine speeds, but substantially more horsepower from 4600 rpm through the 6300 rpm redline than expected, coupled with considerable torque increases both at low and mid rpm and at high engine speed.
At low rpm, the VTEC intake valves follow a set of low-lift, short-duration cam lobes with timing that optimizes cylinder filling. Additionally, the timing of the intake valves is staggered and their lift is asymmetric, creating a swirl effect within the combustion chambers. This increases burn speed and improves combustion stability and EGR rate. As the engine accelerates through 3500 rpm, the intake rocker arms transition to actuation by high-lift, long-duration cam lobes designed to optimize high rpm output.
NEW INDUCTION SYSTEM/PGM-FI
Controlled by a 16-bit, 32 Mhz Central Processor Unit (CPU), the TL's Programmed Fuel Injection (PGM-FI) monitors throttle position, engine temperature, intake manifold pressure, atmospheric pressure, exhaust gas oxygen content and intake air temperature and tracks the operation of the engine with position sensors on the crankshaft and both camshafts. The PGM-FI CPU is in constant communication with a similar CPU that controls the 5-speed automatic transmission. It controls fuel delivery to six injectors mounted in the new cast aluminum, tuned-length intake manifold. The new intake manifold features a large plenum chamber to help maximize air flow and increase power and torque.
The TL high-flow dual exhaust system is newly designed to offer lightweight, minimal noise and vibration and excellent emissions control. Not only does the dual-exhaust design provide greater performance, its compact design reduces intrusion into the cabin and trunk areas. For 2000, increased diameter as well as thickness of the exhaust manifold help reduce emissions by speeding up catalytic converter light-off.
DIRECT IGNITION SYSTEM/KNOCK CONTROL
Proper ignition spark timing is critical to engine performance and emission control. Unfortunately, the correct ignition timing is a moving target, changing from one instant to the next depending on a multitude of factors. Too little spark advance for the conditions and efficiency suffers; too much and the onset of knocking (or pinging) can result in overheating and engine damage. To ensure a properly timed spark, the TL relies on a new generation knock-control system. Based on a centrally positioned sensor in the block that "hears" the first traces of knocking, the ignition timing is advanced to the point of peak efficiency, but not beyond, even if fuel quality is less than the specified unleaded premium. This fine spark control allows the TL to operate safely--and more efficiently-with greater spark advance than its predecessor.
Another refinement to the ignition system is the adoption of improved direct ignition coil units, which are positioned directly in the spark plug access bores. Less than half the weight of the units used on the previous-generation TL, the direct coil units are more compact and more reliable.
CONTROL OF NOISE, VIBRATION AND HARSHNESS
During development of the Acura V-6 powertrain, special effort was devoted to attaining higher standards of Noise, Vibration and Harshness (NVH) control. Key competitive engines were analyzed to develop engineering targets for smoothness and noise control. The engineering exhibited in the TL reflects this effort with features like the compact, rigid aluminum block and its unusually high resonant frequency, rigid forged crankshaft, die-cast accessory mounts and stiff cast aluminum oil pan.
100,000-MILE TUNE-UP INTERVALS
The TL's first scheduled tune-up is required at 100,000 miles; during that time only routine inspections and fluid changes are required. The roller-follower design of the VTEC valve train cuts friction and wear to the point that the screw-type tappet clearance adjusters need not be checked until 100,000 miles, at which point the platinum-tipped spark plugs are also due for replacement.
DIRECT-ACTING CRUISE CONTROL
When the cruise control is engaged, the cruise control Electronic Control Unit (ECU) directly commands downshifts to the transmission ECU as required, allowing the TL to more closely maintain the set road speed even in hilly driving conditions. The convenient steering wheel-mounted cruise control buttons allow the driver to adjust speed in 1 mph increments or disengage the cruise control without touching the brake pedal.
TRACTION CONTROL SYSTEM
Given the TL's formidable power output and the need for all-weather drivability, a Traction Control System (TCS) is standard equipment. This low-speed system operates at vehicle speeds below about 25 mph by applying one or both front brakes to control wheelspin when necessary. This independent wheel control provides a limited-slip differential effect that substantially improves performance on surfaces with split traction coefficients. Relative to the previous generation TL, which used throttle control only to limit wheelspin, the new TL delivers up to 30 percent better acceleration and climbs hills much more easily in start-up split-traction situations.
NEW 5-SPEED SPORTSHIFT AUTOMATIC TRANSMISSION
Though advances in usable engine power output play a significant role in the 2000 TL's quicker acceleration, its new 5-speed automatic transmission figures heavily in measured performance gains and seat-of-the-pants driving feel. Its closer ratio settings closely matches the demands of varied driving situations. Plus, the new transmission's taller top gear ratio (lower numerically) results in a lower cruising rpm for reduced engine noise and lower fuel consumption. In the EPA highway driving cycle, preliminary figures show a 2 mpg increase to 29 mpg.
Immediately noticeable from the driver's seat is a marked improvement in shift quality, relative to the four-speed automatic transmission in the '99 TL. The new 5-speed transmission downshifts more quickly, with less shift shock.
By sharing the idler and third gear clutches, the new transmission provides a total of five ratios without a significant increase in size or weight over the 4-speed transmission it replaces. And there are other refinements too, such as a new, 1st gear one-way clutch for smoother shifts and a new heat exchanger design that moderates transmission operating temperature more quickly and with less complexity than the old system. The lockup torque converter engagement area has been increased too, to provide more positive engagement over a broader range of driving speeds.
Using Direct Control shift technology, the new transmission (like the '99 version) uses a 16-bit, 20 Mhz ECU directly controlling transmission operation in concert with the engine management system. Linear solenoids provide precise, real-time control of the clutch on/off pressure in the TL's transmission. With superior clutch-engagement accuracy, the sophisticated control logic system operates smoothly under all conditions. To reduce noise, a bearing supports the idle shaft, and the gear-mesh contact ratio was refined.
Multiple safety and control strategies use interaction between engine and transmission controllers to manage overall powertrain operation. By limiting engine output torque and/or transmission clutch pressure, sharp driveline shocks are eliminated. The engine is also prevented from exceeding 5000 rpm in neutral and park.
GRADE LOGIC CONTROL
By monitoring throttle position, vehicle speed and acceleration/deceleration then comparing these inputs with a map stored in the transmission computer, the TL Grade Logic Control System "knows" when the car is on a hill. The shift schedule is then adjusted automatically to hold the engine in a lower gear for better climbing power, increased downhill engine braking and decreased shift frequency.
To complement the TL's sporting nature, the standard automatic transmission features a SportShift mode similar to the one originally introduced in the NSX sports car. Although somewhat different in design, the SportShift mode puts gear selection in the hands of the driver, much like a manual transmission. By moving the console-mounted transmission selector handle to the left of the drive position into a special SportShift gate, upshifts and downshifts can be commanded with a quick fore or aft motion. Gear selection is indicated by an LED display positioned prominently in the tachometer face.
To foster the immediate feel of a manual transmission, in SportShift mode, the transmission logic commands firmer shifts that are approximately 10 percent quicker than in automatic mode. Additionally, the system is engineered to deliver an unusually quick response time to shift commands as compared to other semi-manual automatic transmissions.
Typically, the TL's transmission responds to a shift command in just 0.35 second, with the total shift completed in just over 0.9 second from the initial lever movement. These figures are quicker than those of semi-manual automatic transmissions of sports cars costing more than twice as much as the TL.
The SportShift system parallels the operation of a manual gearbox, with built-in safety override features. The logic will not allow a downshift that would cause the engine to over-rev in the driver-selected lower gear; the transmission will stay in the selected gear until the vehicle comes to a complete stop and then will shift into first should the driver forget to do so. During acceleration, except for shifting between 1st and 2nd, the transmission will not up-shift automatically in SportShift Mode; however, should the driver fail to command an upshift in time, the engine ECU's soft fuel cut-off between 6400 and 6600 rpm will prevent the engine from over revving. Should the engine be forced to rev beyond its fuel cut-off point for an extended period of time, the transmission will upshift automatically to prevent engine damage.