2005 Acura TSX - Powertrain Part 1

The TSX is a precisely engineered sports sedan that blends agility and handling with 5-passenger comfort. That delicate balance of attributes drove every aspect of development, including the selection of the powertrain. When it came to choosing a powertrain configuration for the TSX, the path soon became clear. A V-6 like that in the TL would deliver abundant power, but would increase the size and weight of the car, and move the TSX away from its sporting intentions. An in-line 4-cylinder, using the latest Acura technologies, would make for a lighter, well-balanced, more compact vehicle that put the emphasis on overall sporting performance and handling responsiveness.

Power for the TSX comes from an advanced 2.4-liter DOHC i-VTEC in-line 4-cylinder that builds on the technology found in the RSX Type-S sports coupe. With an 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.

The all-aluminum powerplant has four-valves-per-cylinder and free-flowing intake and exhaust systems that combine to deliver 200 horsepower at 6800 rpm- a figure that betters the European competition by up to 32 horsepower. The strong 166 pound-feet of torque at 4500 rpm and 21/30 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 has gotten even smarter. The electronically controlled throttle and transmission work together to choreograph shifts, resulting in smooth shifts.

POWERTRAIN

AT A GLANCE

Engine

• 2.4-liter, DOHC, i-VTEC 4-cylinder engine that produces 200 horsepower at 6800 rpm and 166 lbs.-ft. of torque at 4500 rpm
• i-VTEC "intelligent" valve-control system adds VTC (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
• 110,000-mile tune-up intervals

• Estimated mileage of 22/31 mpg (City/Highway, 5 AT) and 21/30 mpg (City/Highway, 6 MT) (based on EPA method)
• 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

6-Speed Manual Transmission

• Close-ratio 6-speed improves performance and fuel efficiency
• Compact, lightweight magnesium transmission case and bellhousing (the first in an Acura vehicle)
• 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

5-Speed Sequential SportShift Automatic Transmission

• Quick-response 5-speed Sequential SportShift 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 (NV)

• Chain-driven balance shafts mounted on lower block in oil pan
• Maintenance-free silent-chain camshaft drive
• Aluminum block with cast-in, centrifugally cast iron cylinder liners for light weight and durability
• Aluminum block and one piece aluminum crankshaft carrier for improved strength
• Maintenance-free serpentine accessory drive with auto-tensioner

i-VTEC VALVE-CONTROL SYSTEM

The TSX features the latest iteration of the Variable Valve Timing and Lift Electronic Control (VTEC) system that first appeared in the Acura NSX supercar. By varying valve lift based on key engine parameters, VTEC lets the engine develop strong low-end torque and exceptional high rpm power. The TSX engine features the "intelligent" i-VTEC system, which first appeared in the RSX Type-S sports coupe. This "intelligent" system adds VTC (Variable Timing Control) to VTEC to provide continuously variable camshaft timing. By allowing the valve lift and valve timing to be adjusted to suit the engine's operating parameters from moment to moment, i-VTEC provides substantial performance, efficiency and emissions improvements.

VTEC (Variable Timing and Lift Electronic Control)

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, 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 mixing in the cylinders, burn speed and combustion stability are improved. As engine rpm builds, VTEC transitions to a high-lift, long-duration cam profile for improved high-rpm engine output.

The TSX uses a variation of this technology that is very similar to that of the NSX. 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 cam profiles, for maximum high rpm horsepower.

VTC (Variable Timing Control)

The i-VTEC system incorporates VTC (Variable Timing Control), 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 monitors cam position, intake manifold pressure and engine rpm, then commands a VTC actuator to advance or retard the intake cam, optimizing engine output and reducing emissions. At idle, the intake cam is almost fully retarded to deliver a stable idle and reduce oxides of nitrogen (NOx) emissions. The intake cam is progressively advanced as rpm builds, so the intake valves open sooner and valve overlap increases. This reduces pumping losses, which increases fuel economy and further reduces exhaust emissions due to the creation of an internal exhaust-gas recirculation effect. By continuously optimizing the amount of intake cam advance or retard based on the operating conditions, the TSX engine is both powerful and exceptionally flexible.

DRIVE-BY-WIRE THROTTLE CONTROL SYSTEM

An electronic drive-by-wire 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 and 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 that the way the TSX responds to throttle pedal movements is 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 that there's ample response for passing. The system also alters response based on the road slope, providing more throttle gain on uphills, and less on downhills, and also reduces changes in gain on curvy roads to make the car easy 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. That means 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 internal upgrades give the motor greater resistance to vibration.