2005 Acura RSX Powertrain
9/1/2004 4:17:27 AM
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.
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 engine in the high-performance RSX Type-S model adds a high-performance version of the i-VTEC system and a fixed, high-volume intake manifold. To make the Type-S even more exciting to drive for 2005, the Type-S engine receives substantial enhancements to its intake and exhaust systems as well as high performance camshafts to boost horsepower from 200 at 7400 rpm to 210 at 7800 rpm and increase torque from142 lb-ft. at 6000 rpm to 143 lb-ft. at 7000 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) tailpipe emissions standards. Engine, fuel tank and catalytic converter modifications made for 2005 have lowered evaporative emissions by 75 percent to achieve a LEV2 Evaporative Emissions rating.
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 short-throw 6-speed manual transmission. The final gear ratio has been lowered by 8.6 percent for 2005 to complement the additional horsepower and provide enhanced acceleration. 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. Synchronizers (triple cone on gears 1 and 2, double cone on gears 3 and 4, and new for 2005, single cone carbon on gears 5 and 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
- RSX Type-S engine output increased for 2005 from 200 to 210 horsepower at 7800 rpm-at over 100 horsepower per liter, one of the highest specific outputs of any production engine in the world-and 143 lb-ft of torque at 7000 rpm
- i-VTEC "intelligent" valve-control system adding VTC (Variable Timing Control) to VTEC
- Computer-controlled Programmed Fuel Injection (PGM-FI)
- High performance camshafts
- RSX engine utilizes dual-stage intake manifold
- Direct Ignition System
- 110,000-mile tune-up intervals
- RSX delivers estimated EPA fuel economy of 27/33 mpg (city/highway) when mated to the 5MT and 25/34 mpg (city/highway) when mated to the 5AT.
- RSX Type-S delivers estimated EPA fuel economy of 24/31 mpg (city/highway)
- Both engines meet strict Low Emission Vehicle-II (LEV 2) tailpipe emissions 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
- Lower final gear ratio for 2005 for quicker acceleration
- 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
- Two high-rigidity rubber mounts, and one hydraulic mount 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
i-VTEC VALVE-CONTROL SYSTEM
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 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 streamlined version for the RSX, and
a high-performance version for the Type-S.
The 160 horsepower RSX employs a 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 210 horsepower RSX Type-S uses the same high-performance a three rocker arm VTEC design as the NSX, to vary 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.
CYLINDER HEAD / VALVETRAIN
The RSX engine uses an aluminum cylinder head and a double-overhead-cam, four-valve-per-cylinder valvetrain incorporating the i-VTEC system. A generous "squish" area around the combustion chambers yields increased gas turbulence for faster flame propagation and excellent efficiency.
For 2005, high performance camshafts were applied on RSX Type-S models. Increases in both the intake and exhaust valve opening angles boost the rate that air moves into and exhaust moves out of the cylinder. At high engine speeds, valve lift on the intake side is increased by five degrees and on the exhaust side by 10 degrees compared to the previous model. The new camshafts increase engine breathing and help deliver enhanced top-end horsepower. The camshafts are operated by a silent-chain drive that helps provide smooth, refined performance while also being maintenance-free.
ENGINE BLOCK / CRANKSHAFT
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.
DUAL-STAGE INTAKE MANIFOLD (RSX MODEL)
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.
SHORT-LENGTH PERFORMANCE-TUNED INTAKE MANIFOLD WITH HIGH-FLOW INTAKE DUCT (RSX TYPE-S MODEL)
On the Type-S powerplant, a short, high-performance single-stage manifold is used to help boost high-rpm power. For 2005, the diameter of the intake duct was enlarged 11 percent from 63 mm to 70 mm to increase intake flow, especially at high rpm. In addition to increasing flow, this larger intake duct creates more sport sound, the deep, throaty rumbling produced by the engine under hard acceleration.
PROGRAMMED FUEL INJECTION (PGM-FI)
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 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 high-density catalytic converter for improved light-off performance and reduced hydrocarbons and NOx. Emissions performance is further improved thanks to the engine's 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 210 horsepower, the exhaust system has been retuned for 2005 to increase exhaust flow. By employing a larger diameter tail pipe (70 mm compared to 60.5 mm on the previous Type-S), and by reducing the density of the ceramic substrate in the catalytic converter, exhaust flow was increased from 95 liters per second to 98 liters per second.
NOISE, VIBRATION AND HARSHNESS (NVH) CONTROL
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). Engine mounts, two of which are liquid filled, and reinforcements in the engine compartment help further reduce engine noise and vibrations. To complement the additional horsepower for 2005, Type-S models receive an additional engine mount damper added to the subframe to help reduce rocking and isolate powertrain NVH from the passenger compartment.
110,000-MILE TUNE-UP INTERVALS
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).
5-SPEED MANUAL TRANSMISSION (RSX)
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 high-friction clutch material for improved performance, long life, easy engagement, and reduced friction area.
5-SPEED SEQUENTIAL SPORTSHIFT AUTOMATIC TRANSMISSION (RSX)
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 innovative 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.
GRADE LOGIC CONTROL (5-AT)
To improve powertrain smoothness and reduce gear "hunting" on steep
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.
6-SPEED MANUAL TRANSMISSION (Type-S)
To provide driving enthusiasts with exceptional control and feel, the high-performance RSX Type-S is available exclusively with a short-throw, close-ratio 6-speed manual transmission. The gear ratio for the 2005 model has been reduced 8.6 percent to maximum the engine's torque for quicker acceleration. By employing multiple large-capacity synchronizers (triple cones on gears 1 and 2; double cones on gears 3-4), the 6-speed offers an exceptionally light effort. For 2005, single cone carbon synchronizers replaced double cone brass synchronizers on gears 5 and 6, for increased friction capability and reduced shift effort. 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 lightweight and compact. In addition, it employs a wide-angle, clutch-torsion mechanism with two-stage hysteresis to greatly reduce the gear rattling that plagues many conventional 6- speed transmission designs.
Further refining the transmission's sporty, high-quality feel is a short-stroke clutch pedal for quicker shifting, a hydraulic damper integrated with the master cylinder for reduced clutch vibration, and an innovative clutch-friction material for improved clutch engagement feel.