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2004 Acura RSX -- Powertrain


The two engines offered in the Acura RSX incorporate a host of innovative features designed to deliver a cutting-edge combination of performance, fuel efficiency, and low emissions. Most apparent is the i-VTEC "intelligent" valve-control system, a technology that combines VTC (Variable Timing Control)-which continuously adjusts camshaft phase-with Variable Valve Timing and Lift Electronic Control (VTEC) -- which changes valve lift, timing, and duration. Combining these two systems results in impressive horsepower and high torque with outstanding fuel economy and low exhaust emissions. In addition, the RSX's transversely mounted engine block has been rotated 180 degrees, bringing the exhaust manifold closer to the catalyst for improved light-off and reduced emissions at start-up.

The RSX engine is an all-aluminum, 2.0-liter inline four-cylinder design that uses 16 valves, a dual-stage intake manifold, and the i-VTEC system (VTC on intake cam shaft only) to deliver 160 horsepower at 6500 rpm and 141 lb-ft. of torque at 4000 rpm.

The 2.0-liter 4-cylinder in the high-performance RSX Type-S model adds a high-performance version of the new i-VTEC system and a fixed, high-volume intake manifold. These features help boost output to 200 horsepower at 7400 rpm and 142 lb-ft. of torque at 6000 rpm.

In keeping with Acura's proven commitment to the environment, both the RSX and Type-S engines meet strict Low Emission Vehicle-II (LEV-II) standards.

The RSX comes with either a quick-shifting 5-speed manual transmission or an electronically controlled, 5-speed automatic transmission with Acura's Sequential SportShift system. Inspired by the transmissions used in Formula One race cars, Sequential SportShift allows the driver to shift the forward gears semi-manually or enjoy the shifting ease of a conventional automatic.

The RSX Type-S is available exclusively with a new short-throw 6-speed manual transmission. Designed to be compact and lightweight, the 6-speed has also been engineered to provide the lightning-quick shift action of a race car transmission. Multiple synchronizers (triple cone on gears 1 and 2, double cone on gears 3-6) help reduce shifting load for a light, responsive feel. The Type-S also includes a short-throw clutch with a torsion mechanism that considerably reduces gear rattle.

Powertrain At A Glance


RSX 2.0 Liter, DOHC, 4-cylinder engine produces 160 horsepower at 6500 rpm and 141 lb-ft. of torque at 4000 rpm
Type-S engine produces 200 horsepower at 7400 rpm-at 100 horsepower per liter, one of the highest specific outputs of any production engine in the world-and 142 lb-ft of torque at 6000 rpm
i-VTEC "intelligent" valve-control system adding VTC (Variable Timing Control) to VTEC
Computer-controlled Programmed Fuel Injection (PGM-FI)
RSX engine utilizes dual-stage intake manifold
Direct Ignition System
110,000-mile tune-up intervals
Emissions/Fuel Economy

RSX delivers estimated EPA fuel economy of 27/33 mpg (city/highway)
RSX Type-S delivers estimated EPA fuel economy of 24/31 mpg (city/highway)
Both engines meet strict Low Emission Vehicle-II (LEV-II) standards
5-Speed Manual Transmission (RSX)

Quick, light shifting effort
5-speed design for excellent performance
5-Speed Sequential SportShift Automatic Transmission (RSX)

Quick-response 5-speed Sequential SportShift allows semi-manual operation
Full driver-selectable control in SportShift mode-transmission will not shift unless directed to do so by driver
Wide-ratio design carefully matched to engine's power band for improved performance and efficiency
Second-gear "hold" function in SportShift mode for improved take-off on snow or other slippery surfaces
Easy gear selection through fewer gate positions (5), which makes finding the desired gear more intuitive
Grade Logic Control for reduced gear "hunting" when driving on steep hills
Linear solenoid direct-acting control (world's first) for reduced shift shock and improved shift smoothness and responsiveness
6-Speed Manual Transmission (Type-S)

Exceptionally short throws for "race car" shift feel
Close-ratio 6-speed helps improve performance and fuel efficiency
Advanced clutch torsion mechanism reduces rattling noise
Hydraulic damper integrated with master cylinder for reduced pedal vibration
Short clutch-pedal stroke for effortless shifting
Advanced friction material for improved clutch operability
Noise, Vibration, and Harshness (NVH)

Aluminum block with cast-in iron liners for light weight and durability
One-piece crankshaft carrier with ferrous main bearing caps for improved rigidity and durability
Four engine mounts: two high-rigidity rubber mounts, two hydraulic mounts for reduced engine vibration
Lightweight alloy pistons and forged steel connecting rods
Maintenance-free serpentine accessory drive with auto tensioner
Maintenance-free silent-chain camshaft drive

The innovative Variable Valve Timing and Lift Electronic Control (VTEC) system made its debut on the Acura NSX supercar, delivering abundant low-rpm torque, exhilarating high-rpm power, and outstanding fuel efficiency.

The RSX features the latest version of this remarkable engine system: i-VTEC. The "intelligent," i-VTEC system adds new VTC (Variable Timing Control) to VTEC to provide continuously variable camshaft timing-taking the concept of variable valve timing to new heights. In short, i-VTEC = VTEC + VTC. Not only does i-VTEC provide a substantial performance increase across a broad power band, it boosts fuel economy while also reducing engine emissions.

VTEC (Variable Timing and Lift Electronic Control)

The innovative VTEC system adjusts the lift and opening duration of the valves to help the engine produce both abundant low-rpm torque and excellent high-rpm power. At low rpm, VTEC adjusts valve timing and lift for optimum cylinder filling. In addition, the timing of the intake valves is staggered and their lift asymmetric-creating a swirl effect within the combustion chambers. The result is increased burn speed with improved combustion stability. As engine rpm builds, VTEC transitions to a high-lift, long-duration cam profile for improved high-rpm engine output.

The RSX uses two variations of VTEC, a new streamlined version for the RSX, and a high-performance version for the Type-S.

The 160 horsepower RSX employs a new version of VTEC to boost performance and reduce emissions that applies variable timing and lift to the intake valves only. Additionally, the RSX system is further simplified by utilizing only two rocker arms per pair of intake valves (instead of the usual three). During low rpm operation, intake air is drawn almost exclusively through the primary intake valve, thereby creating a very strong swirl effect to maximize combustion. At 2,200 rpm, the secondary rocker arm engages the primary rocker causing both intake valves to open for the same lift and duration, substantially increasing airflow into the cylinder and boosting performance.

The 200 horsepower RSX Type-S uses the same high-performance VTEC design as the NSX, a three rocker arm system that varies the lift and duration of both the intake and exhaust valves for maximum power output. At lower rpm, the valves follow low lift, short duration camshaft profiles to help boost low-end torque. Above 5,800 rpm, the intake and exhaust valves are operated by high-lift, long-duration cam profiles, for maximum high rpm horsepower.

When combined with VTC, both versions help the RSX engine produce a remarkably broad and smooth power band with exceptional torque and horsepower.

VTC (Variable Timing Control)

The i-VTEC system adds VTC (Variable Timing Control) to VTEC for continuously variable camshaft phasing across the engine's entire power band. As engine rpm builds, a VTC actuator-controlled by an engine-control unit that monitors cam position, ignition timing, exhaust oxygen content, and throttle position-advances or retards the intake cam throughout the 50 degree range, optimizing engine output and reducing emissions.

During typical operation, the intake camshaft timing is almost fully retarded at idle to help provide more stable idling while reducing exhaust emissions (NOx). As rpm increases, the intake camshaft is advanced, opening the intake valve sooner and providing additional valve overlap. This results in increased fuel economy (by reducing pumping losses) and a further reduction in exhaust emissions (by creating a large, internal exhaust gas re-circulation effect).

Also, to generate additional power throughout the rev range, the intake camshaft is continuously varying the amount of advance or retard, instantly adjusting to provide additional power as required by the driver.


The RSX engine uses an aluminum cylinder head and a double-overhead-cam, four-valve-per-cylinder valvetrain incorporating the new i-VTEC system. A generous "squish" area around the combustion chambers yields increased gas turbulence for faster flame propagation and excellent efficiency. The camshafts are operated by a silent-chain drive that helps provide smooth, refined performance while also being maintenance-free.


The RSX engine features a compact aluminum block with cast-in iron liners-a design known for its light weight, high rigidity, and excellent durability. The block has a one-piece aluminum crankshaft carrier, which has ferrous-carbon inserts in the bearing caps for additional strength. The Type-S version also incorporates a stiff, cast-aluminum oil pan. The crankshaft is a highly rigid, forged-steel design that uses a special micro-polished surface finish for reduced friction and increased durability.

In addition, the Type-S engine uses high-strength connecting rods and crankshaft as well as high-compression cast-aluminum pistons.

In the RSX, the transversely mounted engine block has been rotated 180 degrees, bringing the exhaust manifold closer to the catalyst for improved light-off and reduced emissions at start-up.


On the 160 horsepower RSX engine, a dual-stage intake manifold utilizes two intake runners for each cylinder, one longer than the other. Below 4600 rpm, only the longer of the two runners delivers air to the cylinder-taking advantage of the inertia effect of the long intake path. Above 4600 rpm, however, a rotary valve in the bore of the short runner opens to allow the passage of additional air to the cylinder. This has the effect of boosting midrange and high-rpm power by utilizing the inertia effect at both low and high rpm.


On the Type-S powerplant, a short, high-performance single-stage manifold is used to help boost high-rpm power.


Both RSX engines are equipped with a Programmed Fuel Injection (PGM-FI) system. The system monitors throttle position, engine temperature, intake-manifold pressure, atmospheric pressure, exhaust-gas oxygen content, and intake-air temperature. It controls fuel delivery by four newly developed, multi-holed injectors mounted in the cast-aluminum intake manifold. The ECU also tracks the operation of the engine with position sensors on the crankshaft and both camshafts.


A stainless-steel, low heat-mass exhaust system is standard on the RSX. The system employs a new, high-density catalytic converter for improved light-off performance and reduced hydrocarbons and NOx. Emissions performance is further improved thanks to the engine's new design, which positions the exhaust manifold on the rear of the engine-which shortens the distance that the exhaust gases must travel to the catalytic converter, resulting in faster light-off and more complete conversion of the exhaust gases. The exhaust system also incorporates an "e-shaped" dual-path pipe that optimizes the exhaust flow for improved torque and lower emissions.

To help the Type-S produce 200 horsepower the exhaust system has been tuned to further reduce backpressure.


In addition to their outstanding power and response, the RSX engines have been engineered for class-leading smoothness and refinement. To that end, the 2.0-liter four-cylinder employs such NVH-reducing features as highly rigid, ferrous-carbon inserts in the main bearing caps for added rigidity, a one-piece crankshaft carrier, a silent chain cam drive, and a stiff, cast-aluminum oil pan (Type-S). Four engine mounts (two liquid-filled) and reinforcements in the engine compartment help further reduce engine noise and vibrations.


The RSX's first scheduled engine tune-up is required at 110,000 miles (only routine inspections and fluid changes are required up to this point). Credit for this longevity goes to long-wearing platinum-tipped spark plugs, a long-life timing chain, and careful engineering of the precisely manufactured DOHC valvetrain-which reliably maintains proper valve tappet clearances until the 110,000-mile first tune-up (under normal conditions).


The RSX comes with a 5-speed manual transmission equipped with a short-stroke shift linkage for superb shifting quickness and feel. For smooth, progressive shift engagement and low clutch-pedal effort, the transmission includes a refined hydraulic clutch unit. The transmission also uses a new clutch friction material for improved performance, long life, easy engagement, and reduced friction area.


A 5-speed Sequential SportShift automatic transmission is available as an option on the RSX. Exceptionally lightweight and compact, the 5-speed automatic is designed to provide best-in-class performance and superb fuel economy.

The RSX 5-speed reduces shift shock and improves shift smoothness-thanks to a linear solenoid direct-acting control with new control logic. A highly intuitive shift-gate design enhances shifting ease.

The RSX 5-speed automatic is equipped with a Sequential SportShift system similar to the one originally introduced in the NSX sports car. The SportShift transmission operates as an automatic or 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 located between the tachometer and speedometer.

To foster the immediate feel of a manual transmission, in SportShift mode the transmission logic commands firmer shifts that are quicker than those made in automatic mode. Additionally, the system is engineered to deliver an unusually quick response time to shift commands as compared with other semi-manual automatic transmissions.

The Sequential SportShift system parallels the operation of a manual gearbox, but 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 approaches a complete stop, and then will shift into first automatically. During acceleration, the transmission will not upshift automatically in SportShift mode; however, should the driver fail to command an upshift in time, the engine ECU will cut off the fuel flow to prevent the engine from over-revving. If the over-revving continues after the fuel cut, the transmission will upshift automatically.


To improve powertrain smoothness and reduce gear "hunting" on steep grades, the

5-speed automatic transmission is also equipped with a standard Grade Logic Control system. Using sensors that monitor throttle position, vehicle speed, and acceleration/deceleration and then comparing these inputs with a map stored in the transmission computer, the system is able to determine when the vehicle is on an incline and adjust the shift schedule for improved climbing power or downhill engine braking.


To provide driving enthusiasts with exceptional control and feel, the high-performance RSX Type-S is available exclusively with a new, short-throw, close-ratio 6-speed manual transmission. By employing multiple large-capacity synchronizers (triple cones on gears 1 and 2; double cones on gears 3-6), the 6-speed offers an exceptionally light effort-while an extremely short-stroke shift lever provides the quick and precise shift response normally associated with racecar transmissions.

Despite its high-performance 6-speed design, the RSX transmission is actually the same weight and is even more compact than the 5-speed manual transmission in the Integra GS-R. In addition, it employs a new wide-angle, clutch-torsion mechanism with two-stage hysteresis to greatly reduce the gear rattling that plagues many conventional 6- speed transmission designs.
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