Overview
For 1998, a single potent, powertrain drives the TL. The new 3.2 liter VTEC-equipped engine is substantially lighter than its predecessor, develops more horsepower and torque, delivers improved acceleration and superior fuel economy. Relative to its prime competition, the new TL develops more power and accelerates faster, while delivering competitive fuel economy. The new 60-degree, 24-valve, V-6 engine is mounted transversely in the chassis, improving packaging efficiency. (The previous engine had a 90-degree V-angle, and was positioned longitudinally in the chassis.) It is coupled with a sequential SportShift four-speed automatic transmission with Grade Logic Control that drives the front wheels, with the assistance of a standard traction control system. The complete TL powertrain is manufactured at Honda of America's plant in Anna, Ohio.
Power
- 225 hp (a 25-hp, or 11% increase compared to previous V-6)
- Torque is increased from 209 lb.-ft to 216 lb.-ft
- Equipped with VTEC cynlinder heads with roller cam-follower rocker arms
- Compression ratio raised from 9.6:1 to 9.8:1
- Compact, lightweight drivetrain is 18% lighter than its predecessor
- Improved fuel economy 19/27 mpg (unofficial, estimated City/Hwy), up from 19/24 mpg
- Acceleration from 0-60 mpg has been improved from 8.5 seconds to 8.2 seconds
Emissions/Fuel Economy
- TLEV emission level (California models only)
- Electronically controlled EGR (Exhaust Gas Recirculation)
- Improved engine startability system
- VTEC
NVH
- Smooth running 60-degree V-angle
- Full floating piston pins eliminate piston slap during warm-up
- Elimination of seperate camshaft holders allows for a more compact, rigid cylinder head
- Lightweight pistons connecting rods
- Three hydraulic engine mounts
- Cast aluminum oil pan
- Transmission gear noise improvement through tighter gear teeth mesh contact ratio
Transmission
- Quick-response sequential SportShift allows semi-manual operation
- Direct-control automatic transmission is managed by the PCM (Powertrain Control Module) for smoother shifting
- Grade Logic Control provides "smart" shift scheduling in hilly driving
- Simplified, more compact transmission design incroporates improved clutch engagement control
- Smoother Cruise Control operation and reduced shift shock through Cruise Control ECU control of downshifting
Engine Architecture
The TL is powered by a new-generation 3.2-liter, 225-hp, 24-valve V-6 engine. Remarkably compact and lightweight, the TL powerplant and transmission incorporate a wide variety of advanced technologies. Relative to the 1998 TL, total powertrain weight has been reduced by 18%. 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.
Engine Block
Die-cast and heat treated, the compact TL aluminum block is extremely rigid, with a high natural frequency and minimal resonant vibration. Similar to the powerplant in the 3.0CL, the new 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 the same 60-degrees, a departure from the 90-degree V-angle used in the previous-generation TL.
The narrower angle improves smoothness and reduces 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.
Crankshaft/Connecting Rods
The pursuit of compact over all 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 power. 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 Valvetrain
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 VTEC (Variable Valve Timing and Lift Electronic Control) valvetrain is a major contributing factor to the TL's remarkable combination of high power delivery and fuel economy. With the lift and opening duration ofthe 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. Relative to the engine it replaces, the VTEC TL delivers comparable power characteristics at middle engine speeds, but substantially more horsepower from 4600 rpm through the 6300 rpm redline, coupled with considerable torque increases both at low 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 bum 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.
Induction System/PGM-FI
Controlled by a 16-bit, 32 mhz Central Processor Unit (CPU) the TL's Programmed Fuel Injection monitors throttle position, engine temperature, intake manifold pressure, atmospheric pressure, exhaust gas oxygen content, intake air temperature and tracks the operation of the engine with position sensors on the crankshaft and both camshafts. The PGM-FI is in constant communication with a similar CPU that controls the four-speed automatic transmission. It controls fuel delivery to six injectors mounted in a three-piece, cast aluminum tuned-length intake manifold. To enhance the TL's sporting feel, special attention was paia to the engine sound. Key in this effort is the intake runner design, which is tuned to give the engine sound a sporting edge above 3500 rpm.
New startability and cold climate enhancements are built into the TL's induction system. To promote fuel atomization when the engine is less than completely warmed up, a secondary air circuit is opened to the TL's air-assist fuel injection nozzles. This makes the car easier to cold start at high altitude and in cold weather conditions, and results in a reduction in hydrocarbons in tailpipe emissions. Drivability during warm-up is also improved.
Exhaust System
The TL high-flow dual exhaust system was designed to offer light weight, minimal noise and vibration, and excellent emissions control. Not only does the dual exhaust design provide greater performance, it's compact design reduces intrusion into the cabin and trunk areas.
New Generation 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 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 new direct coil units are more compact and more reliable.
Control Of Noise, Vibration and Harshness
During development of the new 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 engineeringtargets 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 valvetrain 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 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
Giventhe TL's increased power output and the need for all weather drivabi1ity,a new 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 wheel spin.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 wheel spin, the new TL in start-up split-traction situations delivers up to 30% better acceleration and climbs hills much more easily.
4-Speed Automatic Transmission
The TL's transmission offers tremendous weight savings over the previous-generation TL transmission. Almost a third lighter, the Direct Control AT is the most significant factor in the new TL's reduced drivetrain weight. More important to the TL's driver is the new transmission's refined feel and quick response. With a 16-bit, 20 mhz Electronic Control Unit (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.
Working in concert with this new system is a canceler mechanism built into the first and second gear clutches that "cancels" out the detrimental effects of rising fluid pressure caused by centrifugal force--assisting in more precise clutch control. The gear train structure has been simplified by eliminating the low-one-way and low-hold clutches. To reduce noise, a bearing to better support the idle shaft has been added, and refinements to the gear-mesh contact ratio have been made.
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, and the engine is prevented from exceeding 5000 rpm in Neutral and Park.
Grade Logic Control
By monitoring throttle position and vehicle speed and 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.
Sequential Sportshift
To complement the TL's sporting nature, the standard automatic transmission features a SportShift mode similar to the one original introdueced 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, individual shifts can be commanded with a quick fore or aft motion. Gear position is indicated by a display positioned prominently in the tachometer face.