2008 Acura TSX - Powertrain
The TSX is a precisely engineered sports sedan that blends agility and handling with 5-passenger comfort. The delicate balance of attributes drove every aspect of TSX development, including the selection of the powertrain. When it came to choosing a powertrain configuration for the TSX, the path soon became clear. An in-line 4-cylinder, using the latest Acura technologies, would make for a lighter, well-balanced, more compact vehicle that puts the emphasis on overall sporting performance and handling responsiveness.
Power for the 2008 TSX comes from an advanced 2.4-liter DOHC i-VTEC® in-line 4-cylinder engine that produces 205 hp net. Incorporating Acura's i-VTEC® "intelligent" valve control system that features Variable Valve Timing and Lift Electronic Control (VTEC®) combined with Variable Timing Control™ (VTC™), the TSX engine delivers formidable power, impressive fuel economy and very low exhaust emissions.
|Engine||I-4 DOHC i-VTEC®|
|Displacement||2354 cc (2.4-liter)|
|Fuel type||Premium Unleaded, 91 Octane|
|Horsepower @ rpm||205 @ 7000|
|Torque @ rpm (lb-ft)||164 @ 4500|
|Transmission||6 MT||5 AT|
|EPA estimated mileage (city/highway)||19/28*||20/28*|
|Emissions certification||EPA Tier 2-Bin 5, CARB LEV-2|
The all-aluminum 2.4-liter powerplant has four-valves-per-cylinder along with free-flowing intake and exhaust systems that combine to deliver 205 horsepower at 7000 rpm. The strong 164 pound-feet of torque at 4500 rpm and 20/28 (city/highway) EPA mileage rating are also highly competitive-a remarkable achievement considering this engine's formidable horsepower output.
Despite its power output, the TSX engine is also very clean. With its rear-mounted exhaust layout, close-coupled catalyst and advanced Programmed Fuel Injection (PGM-FI) the TSX meets strict Tier 2-Bin 5, and Low Emission Vehicle-2 (LEV-2) standards.
The TSX is offered with either a 6-speed close-ratio manual transmission or a 5-speed SportShift automatic. The manual gearbox features a lightweight magnesium alloy case and multi-cone synchronizers. This transmission has a light, quick action and very short shift throws.
The 5-speed SportShift automatic can function as a conventional automatic transmission or, at the driver's option, can be shifted manually for hands-on sporting fun. Working in combination with the drive-by-wire throttle system, the SportShift transmission's shift logic results in quick, smoothly-controlled shifts.
The TSX also features the innovative Maintenance Minder System, which automatically monitors the vehicle's unique operation condition to indicate to the driver when maintenance is required. This system is designed to eliminate unnecessary maintenance procedures to help reduce environmental impact and operating expenses, while ensuring that important service issues are addressed in a timely manner.
Powertrain at A Glance
- 2.4-liter, DOHC, i-VTEC® 4-cylinder engine generates 205 horsepower at 7,000 rpm with 164 lb-ft of torque at 4,500 rpm
- i-VTEC® "intelligent" valve-control system adds Variable Timing Control to VTEC®
- Drive-by-wire throttle control system
- Computer-controlled Programmed Fuel Injection (PGM-FI)
- Dual balance shafts for exceptional smoothness
- Direct ignition system
- Lightweight alloy pistons and high-strength connecting rods
- 100,000 miles or more tune-up intervals (may vary with driving conditions)
- Estimated mileage of 20/28 mpg* (city/highway, 5 AT) and 19/28 mpg* (city/highway, 6 MT)
- Meets strict EPA Tier 2-Bin 5, Carb Low Emission Vehicle-2 (LEV-2) standards
- Rear-facing exhaust ports and under-floor converter provide faster catalyst light-off
*Based on 2008 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.
6-Speed Manual Transmission
- Close-ratio 6-speed manual transmission
- Compact, lightweight magnesium transmission case and bell housing
- Multi-cone synchronization on all gears for light shifting effort
- Short 45 mm shift throws for race-car-like shift feel
- Short clutch pedal stroke with light effort
- Compact clutch with low inertia for quicker acceleration
- Advanced clutch torsion mechanism reduces gear noise
Sequential SportShift 5-Speed Automatic Transmission
- Quick-response Sequential SportShift 5-speed allows semi-manual operation
- Drive-by-wire cooperative control facilitates quicker shifts
- Ratios complement engine's powerband for improved performance and efficiency
- Lockup torque converter design delivers superior fuel economy
- Intuitive 5-position shift gate
- Advanced Grade Logic Control for reduced gear hunting when driving on steep hills
- Linear solenoid direct-acting control for reduced shift shock and improved shift smoothness and responsiveness
Noise, Vibration and Harshness (NVH)
- Chain-driven balance shafts mounted on lower block in oil pan
- Maintenance-free silent-chain camshaft drive
- Aluminum cylinder block with cast-in iron cylinder liners for light weight and durability
- One piece aluminum crankshaft carrier for improved strength
- Maintenance-free serpentine accessory drive with auto-tensioner
i-VTEC® VALVE-CONTROL SYSTEM
The TSX features Acura's Variable Valve Timing and Lift Electronic Control (VTEC®) system. By varying valve lift based on key engine parameters, VTEC® lets the engine develop strong low-end torque along with exceptional high rpm power. In addition, the TSX engine features the "intelligent" i-VTEC® system. This "intelligent" system adds VTC (Variable Timing Control) to VTEC® to provide continuously variable, computer controlled camshaft timing. By allowing the valve lift and valve timing to be continuously adjusted to suit the engine's operating parameters from, i-VTEC® provides further performance, efficiency and emissions improvements.
i-VTEC® is an innovative system that adjusts the lift and opening duration of the valves to help the engine produce strong low-rpm torque and excellent high-rpm power. At low rpm, i-VTEC® automatically adjusts valve timing and lift for optimum cylinder filling. In this low rpm mode, the timing of the intake valves is staggered and their lift is
asymmetric, which creates a swirl effect within the combustion chambers. With better air/fuel mixing in the cylinders, burn speed and combustion stability are improved. As engine rpm builds, i-VTEC® transitions to a high-lift, long-duration camshaft profile for improved high-rpm engine output.
The TSX uses a variation of this technology with three rockers operating each pair of intake and exhaust valves in each cylinder; the TSX powerplant varies the opening lift and duration of the intake and exhaust valves. At low rpm, the valves follow low-lift, short duration camshaft profiles to help boost low-end torque. Above 6000 rpm, the intake and exhaust valves are operated by high-lift, long-duration camshaft profiles, for maximum high rpm horsepower.
Variable Timing Control™ (VTC™)
The i-VTEC® system incorporates Variable Timing Control™ (VTC™), which continuously adjusts the intake cam timing to suit engine operating conditions. This precise control of cam timing benefits power output, fuel economy and emissions performance.
The powertrain control unit (PCM) monitors camshaft position, intake manifold pressure and engine rpm, and then commands a VTC actuator to advance or retard the intake camshaft thus optimizing engine output and reducing emissions. At idle, the intake camshaft is almost fully retarded to deliver a stable idle and reduced oxides of nitrogen (NOx) emissions. The intake camshaft is progressively advanced as engine rpm builds, so the intake valves open sooner and valve overlap increases. This method reduces pumping losses, which increases fuel economy and further reduces exhaust emissions due to the creation of an internal exhaust-gas recirculation effect.
CYLINDER HEAD / VALVETRAIN
The cylinder head is constructed of pressure-cast aluminum alloy and features four-valves-per-cylinder driven by dual overhead camshafts (DOHC). An automatically adjusted silent-type chain drives the camshafts. The chain is maintenance free and runs in an oil bath for maximum durability. The combustion chambers have large "squish" areas to promote faster flame propagation and more complete burning-important factors in reduced carbon monoxide (CO) and hydrocarbon (HC) exhaust emissions.
CRANKSHAFT, ENGINE BLOCK AND OIL PAN
The TSX uses a forged-steel crankshaft with a relatively long 99mm throw. To reduce friction and improve long term durability, the crankshaft journals are micropolished. The die-cast lightweight aluminum cylinder block has cast-in iron cylinder liners with 87mm bores. The liners are made using a unique spin casting, centrifugal process. To maximize the rigidity and minimize noise and vibration, the cylinder block is a 2-piece design that fully supports the five main bearings with a single cast-alloy bed-plate assembly.
PROGRAMMED FUEL INJECTION (PGM-FI)
The i-VTEC® 4-cylinder engine features Programmed Fuel Injection (PGM-FI), which relies on an array of sensors to constantly monitor a number of critical operating variables. PGM-FI tracks throttle position, intake air temperature, water temperature, ambient air pressure (altitude), intake manifold pressure, exhaust/air/fuel ratios and the position of the crankshaft and camshaft. High-efficiency air-assisted fuel injectors deliver fuel to each cylinder. These multi-hole injectors better direct fuel around the intake valve stem for improved atomization, more power output and reduced emissions.
The TSX uses a single-stage intake manifold that is specially tuned for the engine's power characteristics. Fixed-length intake runners are tuned in length, size and shape to provide an optimal blend of low-rpm torque and high-rpm response, while supporting the advanced i-VTEC® valve control system.
Exhaust flow is critical to performance and figures heavily in the strong power characteristics of the TSX. The high-flow rear-mounted exhaust manifold is constructed of stainless steel. Downstream, large diameter pipe sizes increase exhaust flow and the system splits to feed into free-flowing dual silencers and exhaust tips.
DRIVE-BY-WIRE THROTTLE SYSTEM™
An electronic Drive-By-Wire Throttle System™ helps enhance the driving character of the TSX. With smart electronics connecting the throttle pedal to the throttle butterfly in the intake tract, the engine response can be optimized to suit the driving conditions and to better match the driver's expectations. By eliminating the direct throttle cable connection to the engine, the ratio between pedal movement and throttle butterfly movement can be continuously optimized. This adjustable "gain" between throttle and engine is a significant step forward in drivability.
To establish the current driving conditions, the system monitors pedal position, throttle position, vehicle speed, engine speed, calculated road slope, corner radius and engine vacuum. This information is then used to define the throttle control sensitivity.
From the driver's standpoint (because the drive-by-wire system is combined with other functions such as VSA® and Traction Control) this means the TSX responds to throttle pedal movements specifically tailored to the driving conditions. In stop-and-go driving, the pedal response has low gain and is smooth and progressive for easy driving. A similar low-gain response makes starting out on snowy or icy roads more predictable. In low- to medium-speed driving conditions, the gain increases to improve response and acceleration. In high speed driving, the gain increases further still, so there is improved response for passing. The system also alters response based on the road slope, providing more throttle gain uphill, and less downhill, and also reduces changes in gain on curvy roads to make the car easier to control.
The throttle system works with the available SportShift 5-speed automatic transmission to make shifts faster and smoother than has been possible before. By coordinating the throttle opening with the transmission's shifting functions, engine power can be precisely tailored to the needs of the transmission at every point during the shifting process. This concept generates less shift shock and delay, no matter the driving situation.
The TSX uses a DC motor to control the throttle butterfly position in the intake tract. Large bearings and superior internal components give the motor greater resistance to vibration.
The 2008 TSX is compliant with one of the toughest emissions regulations in the United States, the California Air Resources Board (CARB) LEV-2-LEV standard. It also meets the Federally-mandated Tier 2-Bin 5 regulations.
It is the basic architecture of the TSX that forms the foundation for emissions performance of the vehicle. The exhaust port and exhaust system are positioned to the rear of the transversely mounted engine. This means the catalytic converter can be positioned much closer to the engine than is possible with a conventional front-exhaust configuration that sweeps under the engine to reach the catalytic converter. With the under-floor catalyst, light-off of the multi-cell converter is quick after starting. A low heat-mass stainless steel exhaust manifold also speeds converter light-off.
The i-VTEC® cylinder head plays a large role in emissions reduction as well, by fostering internal exhaust gas recirculation, which cuts NOx output. Air-assisted fuel injectors help reduce hydrocarbons after starting, while a Linear Air/Fuel sensor positioned in the exhaust system just upstream of the catalyst improves air/fuel mixture control.
NOISE, VIBRATION AND HARSHNESS (NVH) CONTROL
The high output in-line 4-cylinder engine features comprehensive NVH reduction features. The pressure-cast cylinder block with a bed-plate type main bearing cap delivers a highly rigid assembly, helping to resist overall vibration. A pair of chain-driven balance shafts further smoothes the inherent vibration of a large displacement in-line 4-cylinder engine layout. A self-adjusting silent-type camshaft chain and a serpentine accessory drive belt also reduce NVH.
100,000 MILE TUNE-UP INTERVALS
With a self-adjusting silent-type camshaft chain, long wearing platinum-tipped spark plugs and a precision-engineered valvetrain, the TSX is engineered for low maintenance.
Other than routine fluid changes and inspections, the first scheduled engine tune-up is not required for 100,000 miles or more.
Maintenance Minder™ SYSTEM
To eliminate unnecessary service stops while ensuring that the vehicle is properly maintained, the TSX also includes a Maintenance Minder™ system that automatically monitors the vehicle's operating condition. When maintenance is required, the driver is alerted via a message on the Multi-Information Display (MID).
The MID system monitors operating conditions such as oil and coolant temperature along with engine speed to determine the proper service intervals. Depending on the engine operating conditions, oil change intervals can be extended to a maximum of 10,000 miles, potentially sparing the owner considerable money and inconvenience over the life of the vehicle. The system, which can be reset manually by the owner, monitors all normal service parts and systems, including oil and filter, tire rotation, air-cleaner, automatic transmission fluid, spark plugs, timing belt, coolant, brake pads and more. To prevent driver distraction, maintenance alerts are presented when the ignition is first turned on, not while driving.
6-SPEED MANUAL TRANSMISSION
One of the standard transmissions in the TSX is a close-ratio 6-speed manual gearbox. With exceptionally short 45 mm shift throws (most European sedans have shift throws of about 60-65 mm) and a precise, light shifting action, this manual transmission perfectly complements the car's sporting character. With six forward gear ratios instead of the more common 5-gear arrangement, the TSX has more closely spaced gears for improved acceleration, yet still has a top gear that allows for a low and efficient cruising rpm.
To reduce weight, the compact transmission case and bell housing are cast of a special magnesium alloy-the first use of this lightweight material in the transmission of an Acura product. This complex casting is seven pounds lighter than the comparable aluminum version, and is highly rigid to help damp out noise and vibration. Inside, the gearbox has multi-cone synchronizers on all gears (including reverse) to reduce shifting effort.
A lightweight clutch with low-inertial mass allows the engine to rev quickly, the clutch pedal stroke is short and the use effort is comfortably low. A broad and progressive engagement band of the clutch makes the TSX easy to launch smoothly from a stop. The clutch incorporates a wide-angle clutch-torsion mechanism that reduces the gear rattling sound that is common in many manual-transmission designs.
SEQUENTIAL SPORTSHIFT 5-SPEED AUTOMATIC TRANSMISSION
To deliver the smoothness and convenience of an automatic transmission, coupled with the performance and sporting feel of a manual gearbox, the TSX offers a Sequential SportShift 5-speed automatic transmission. With five closely spaced gear ratios, the automatic transmission helps deliver impressive acceleration performance. An advanced Grade Logic Control System and intelligent shift programming combine with a drive-by-wire throttle control to deliver remarkably swift and smooth shifts along with intuitively correct gear selection. To cope with the engine's additional power output, the capacity of the second gear clutch pack has been increased.
The TSX automatic transmission reduces shift shock and improves shift smoothness with the use of an industry-leading linear solenoid direct-acting control. The TSX also utilizes an intuitive 5-position shift gate design.
The SportShift transmission can be operated in two different modes: fully automatic or with driver-selected ratios. In automatic mode, its Grade Logic Control System provides smart ratio selection regardless road gradient. With sensors that monitor throttle position, vehicle speed and acceleration/deceleration, the system compares these parameters with a map stored in the transmission computer. Based on this information, the system can determine if the vehicle is on an incline and adjusts the shift schedule for improved climbing power or downhill engine braking.
To switch SportShift to the manual mode, the driver simply moves the selector lever to a special gate located to the left of the normal "Drive" position. When in manual mode, a forward push of the lever selects a higher gear and a rearward pull selects a lower gear. An LED display located between the tachometer and speedometer indicates which of the gears is in use.
Shift logic is unique in manual mode, with firmer, faster gear change programming that has a feel similar to that of a manual gearbox. Built-in safety override features make SportShift smarter than any conventional manual transmission, however. Under acceleration, the transmission will hold the selected ratio until commanded to upshift. If the driver doesn't make the upshift in time, the engine ECU will cut off the fuel flow to prevent the engine from over-revving. If the high-rpm condition continues for an extended period even after the fuel is cut (as might be possible on a steep downhill) the transmission will upshift automatically to preclude engine damage. Furthermore, shift logic will not allow a downshift that would cause the engine to over-rev if the driver selects too low of a gear ratio. To avoid the TSX from starting from a stop in a high gear if the driver inadvertently forgets to downshift, the transmission automatically downshifts as the car decelerates to a complete stop.
To accommodate the high-revving engine's horsepower and torque output, a heavy-duty torque converter is used and the countershaft is constructed of high-strength material. To boost efficiency, the transmission has a low-friction clutch and a special super-thin torque converter. The thin torque converter results in a compact transmission unit. Other space saving measures includes a double-row idle gear and a tightly packaged second-gear clutch.
ACTIVE LOCKUP TORQUE CONVERTER
To improve fuel economy while maintaining a high level of drivability, the 5-speed automatic transmission includes an active lockup torque converter. To handle the increased horsepower of the i-VTEC ® engine, Acura strengthened the torque converter by enlarging the diameter of the boss weld to 35mm. With the precise control afforded by a linear solenoid, the system expands the speed and throttle setting range in which lockup can be engaged in the top four gears. The resulting reduction in transmission slippage results in improved fuel mileage in both city and highway driving. This transmission's efficiency and taller (higher numerically) final drive ratio helps the TSX deliver exceptional fuel economy as well as increased performance.
COOPERATION BETWEEN 5AT AND DRIVE-BY-WIRE
With the TSX drive-by-wire throttle system, the operation of the automatic transmission and engine are fully integrated, resulting in remarkable shift smoothness, and a significant reduction in shifting time.