2018 Acura RLX : Powertrain

11/13/2017 11:59:00 AM

For 2018, the Acura RLX continues to offer two distinct high-performance powertrains. The front-wheel drive RLX P-AWS is powered by a responsive 3.5-liter Direct Injection SOHC i-VTEC® V6 engine rated at 310 horsepower and 272 lb.-ft. of torque (SAE net). The RLX engine also incorporates a range of advanced friction-reducing technologies that help boost fuel efficiency and power output. A special intake manifold design, special "tumble" type intake ports, advanced piston crown shapes, an elevated 11.5:1 compression ratio and a variable-flow exhaust system are keys to the high power output. With i-VTEC® (intelligent Variable Valve Timing and Lift Electronic Control) for the intake valves combined with Variable Cylinder Management (VCM) that deactivates the rear bank of three cylinders for greater fuel efficiency, the RLX engine offers broad-spectrum power and fuel efficiency.

RLX Sport Hybrid 3.5L V6 engine and 7DCT

For even greater performance, the RLX Sport Hybrid SH-AWD combines the same 3.5-liter V6 with Acura's advanced three-motor Sport Hybrid all-wheel drive system to deliver a system total of 377 horsepower and 341 lb.-ft. of torque, making it the most powerful Acura sedan in history. In the Acura lineup, only the NSX supercar with its related hybrid powertrain is more powerful.

The RLX Sport Hybrid SH-AWD uses three electric motors: one integrated with the 7-speed dual-clutch transmission that turns with the crankshaft, and a pair of rear motors (Twin Motor Unit) that power the rear wheels. The Twin Motor Unit dynamically distributes electric-motor torque between the left and right rear wheels, providing both positive and negative torque vectoring (negative, through regenerative braking) to aid performance and handling. For 2018, the system features a new, lighter Li-Ion battery pack (-8.2 lbs.) and drive system operating logic enhancements derived from the NSX supercar.

Two transmissions are available in the 2018 RLX. The RLX P-AWS has an all-new, Acura-first 10-speed automatic transmission. Engineered for high efficiency with low weight, low inertia and an exceptionally wide ratio range, the 10-speed automatic maximizes the RLX's performance and fuel efficiency. The RLX Sport Hybrid has a standard 7-Speed Dual-Clutch Transmission (DCT). The DCT offers quick gear changes and eliminates the need for a torque converter, which improves efficiency.

Both RLX powertrains offer exceptional fuel efficiency and emissions performance within their respective classes. RLX P-AWS has EPA fuel economy ratings of 20/29/23 mpg (city/highway/combined) and meets the CARB LEV3 ULEV125 Emissions standard. The RLX Sport Hybrid has EPA fuel economy ratings of 28/29/28 mpg (city/highway/combined) and meets the CARB LEV3 SULEV30 Emissions standards.

RLX Powertrain Specifications

 

2018 RLX P-AWS

2018 RLX Sport Hybrid         SH-AWD

Gasoline Engine type

Aluminum-alloy V6

Aluminum-alloy V6

Displacement, liters

3.5

3.5

Fuel injection

Direct

Direct

Valvetrain

Belt drive, SOHC, i-VTEC® 24-valve with VCM

Belt drive, SOHC, i-VTEC® 24-valve with VCM and idle stop

Gasoline Engine Horsepower @ rpm (SAE net)

310 @ 6500

310 @ 6500

Gasoline Engine Torque @ rpm (lb.-ft.) (SAE net)

272 @ 4500

273 @ 4700

Total Combined Hybrid System Horsepower (SAE net)

NA

377

Total Combined Hybrid System Torque (lb.-ft.) (SAE net)

NA

341

Compression ratio

11.5:1

11.5:1

Redline

6800 rpm

6800 rpm

Transmission

10-speed automatic transmission with Sequential SportShift paddle shifters, Sport Mode, Grade Logic and Shift Hold Control

7-speed dual-clutch transmission (DCT) with Sequential SportShift paddle shifters, Sport Mode, Grade Logic and Shift Hold Control

Drive type

FWD

SH-AWD

EPA Fuel Economy Rating (city / highway/ combined)

20/29/23

28/29/28

Recommended fuel

Premium unleaded
91 octane

Premium unleaded
91 octane

CARB emissions rating

LEV3 ULEV125

LEV3 SULEV30

Tune-up interval

No scheduled tune-ups required for 100,000 +/- miles

No scheduled tune-ups required for 100,000 +/- miles

Powertrains at Glance

  • 3.5-liter, SOHC, V6 engine produces 310 horsepower at 6,500 rpm and 272 lb.ft. of torque at 4,500 rpm (RLX P-AWS) 
  • 3.5-liter, SOHC, V6 engine produces 310 horsepower at 6,500 rpm and 273 lb.-ft. of torque at 4,700 rpm (RLX Sport Hybrid) 
  • i-VTEC® (intelligent Variable Valve Timing and Lift Electronic Control) for intake valves with VCM (Variable Cylinder Management)
  • Computer-controlled Direct Injection (DI) with multi-hole fuel injectors
  • 11.5:1 compression ratio
  • High-strength steel crankshaft
  • X-shaped magnesium intake manifold 
  • Drive-by-Wire™ throttle system
  • Direct ignition system™
  • Detonation/knock control system
  • Variable flow exhaust system
  • Maintenance Minder™ system optimizes service intervals
  • 100,000 +/- miles tune-up interval

Three-Motor Hybrid System (RLX Sport Hybrid)

  • 3.5-liter, SOHC V6 and Sport Hybrid system produce total system power of 377 horsepower and 341 lb.-ft. of torque 
  • Sport Hybrid SH-AWD® (Super Handling All-Wheel Drive™)
  • Front electric motor output: 47 horsepower
  • Dual rear electric motor output: 36 horsepower X 2 (72 combined) 
  • New, lighter Li-Ion battery
  • Eight-year/100,000-mile or ten-year/150,000-mile Li-Ion battery limited warranty, depending on the state of purchase/registration

Emissions/Fuel Economy Ratings

  • High-flow, close-coupled next-generation precious metal catalytic converters plus under floor catalytic converter
  • High capacity 32-bit RISC processor emissions control unit
  • CARB LEV3 ULEV125 emissions compliant (RLX P-AWS) 
  • CARB LEV3 SULEV30 emissions compliant (RLX Sport Hybrid) 
  • EPA 20/29/23 mpg (city/highway/combined) fuel economy ratings (RLX P-AWS)
  • EPA 28/29/28 mpg (city/highway/combined) fuel economy ratings (RLX Sport Hybrid)

Noise & Vibration (NV)

  • 60-degree cylinder V-angle for smooth operation 
  • Automatically tensioned, maintenance-free serpentine belt accessory drive 
  • Active Control engine Mount (ACM) 
  • Active sound control 

Powertrain Control Features

  • Electronic Gear Selector provides fully electronic push-button shift control with Sport mode button
  • Steering wheel mounted racing-inspired paddle shifters
  • Sport mode with remapped, more aggressive automatic shift points and more pronounced engine braking during deceleration
  • Cooperative control between Drive-by-Wire™ throttle system and transmission makes for quicker, smoother shifts
  • Advanced shift-hold control limits up shifts during spirited driving
  • Grade Logic Control System reduces gear "hunting" on steep hills 

Engine Architecture
The RLX 3.5-liter VTEC® V6 has a smooth-firing 60-degree V-angle and compact overall dimensions. The V6 has a die-cast lightweight aluminum alloy block with cast-in-place iron cylinder liners. Direct injection combines with i-VTEC and Variable Cylinder ManagementÔ (VCMÔ) to give the RLX a potent blend of power and fuel efficiency.

In the RLX P-AWS, the aluminum-alloy 24-valve engine produces 310 horsepower at 6,500 and generates 272 lb.-ft. of torque at 4,500 rpm. In the RLX Sport Hybrid, slight calibration differences result in an identical peak horsepower figure combined with a small increase in torque output to 273 lb.-ft. at 4700 rpm.

The RLX P-AWS has an EPA fuel economy rating of 20/29/23 mpg (city/highway/combined); the RLX Sport Hybrid has an EPA fuel economy rating of 28/29/28 mpg (city/highway/combined).

Engine Block and Crankshaft
With its 60-degree V-angle, the RLX's V6 engine is inherently smooth and has compact overall dimensions that allow efficient packaging within the vehicle. The V6 has a die-cast lightweight aluminum alloy block with cast-in-place iron cylinder liners. Made with a centrifugal spin-casting process, the thin-wall liners are high in strength and low in porosity. The block incorporates a deep-skirt design with four bolts per bearing cap for rigid crankshaft support and minimized noise and vibration. The 3.5L V6 uses a high-strength steel crankshaft for reduced weight.

A cooling control spacer positioned in the water jacket surrounding the cylinders helps to maintain consistent operating temperature. Plateau honing of the cylinder linings further lowers internal friction by creating an ultra-smooth surface. This two-stage machining process uses two grinding processes instead of the more conventional single honing process. Plateau honing also enhances the long-term wear characteristics of the engine.

Pistons/Connecting Rods
Designed with special "cavity-shaped" crowns, the pistons help maintain stable combustion and contribute to stratified-charge combustion. Ion-plated piston rings help reduce friction for greater operating efficiency. The compression ratio is 11.5:1. Heavy-duty steel connecting rods are forged in one piece and then the crankshaft connecting rods are "crack separated" to create a lighter and stronger rod with an optimally fitted bearing cap.

Cylinder Heads/ Valvetrain
Like other Acura V6 powerplants, the RLX engine's 4-valve cylinder heads are a single-overhead-camshaft design, with the cams driven by the crankshaft via an automatically tensioned toothed belt. Made of low-pressure cast, low-porosity aluminum, each cylinder head incorporates a "tumble port" design that improves combustion efficiency by creating a more homogeneous fuel-air mixture. An integrated exhaust manifold cast into each cylinder head reduces parts count, saves weight, improves flow and optimizes the location of the close-coupled catalyst.

i-VTEC Valve Control System
The RLX V6 engine combines Variable Cylinder Management (VCM) with Variable Valve Timing and Lift Electronic Control (VTEC), which changes the lift profile, timing and lift duration of the intake valves. A switching mechanism allows each cylinder to operate with low-rpm valve lift and duration or high-rpm lift and duration. The rear cylinder bank's valve gear can also leave all intake and exhaust valves closed to maximize fuel efficiency during cylinder deactivation.

The "intelligent" portion of the system is its ability to vary valve operation based on the driving situation and engine rpm. At low rpm, the VTEC intake valve timing and lift are optimized (low lift, short duration) for increased torque, which allows a wide range of 3-cylinder operation. As engine speed builds past 5,000 rpm, the VTEC system transitions to a high-lift, long-duration intake cam profile for superior high-rpm engine power.

Variable Cylinder Management ™ (VCM™)
The RLX engine employs Acura's Variable Cylinder Management (VCM) cylinder deactivation technology. The VTEC system combines with Active Control engine Mounts (ACM) to allow the VCM system to operate with three cylinders in a wide range of situations to maximize fuel efficiency and lower emissions. When greater power is needed, the system switches seamlessly to 6-cylinder operation. 

During startup, aggressive acceleration, or when climbing hills – any time high power output is required – the engine operates on all six cylinders. During moderate-speed cruising and at low or moderate engine loads, the system operates just the front bank of three cylinders.

VCM can tailor the working displacement of the engine to match the driving requirements from moment to moment. Since the system automatically closes both the intake and exhaust valves of the cylinders that are not used, pumping losses associated with intake and exhaust are eliminated and fuel efficiency gets a further boost. The system combines maximum performance and maximum fuel efficiency – two characteristics that don't typically coexist in conventional engines.

VCM deactivates specific cylinders by using the i-VTEC (intelligent Variable Valve-Timing and Lift Electronic Control) system to close the intake and exhaust valves while the Power Control Module (PCM) simultaneously cuts fuel to those cylinders. The spark plugs continue to fire in inactive cylinders to minimize plug temperature loss and prevent fouling induced from incomplete combustion during cylinder re-activation.

The system is electronically controlled, and uses special integrated spool valves in the cylinder heads. Based on commands from the system's electronic control unit, the spool valves selectively direct oil pressure to the rocker arms for specific cylinders. This oil pressure in turn drives synchronizing pistons that connect and disconnect the rocker arms.

The VCM system monitors throttle position, vehicle speed, engine speed, automatic-transmission gear selection and other factors to determine the correct cylinder activation scheme for the operating conditions. In addition, the system determines whether engine oil pressure is suitable for VCM switching and whether catalytic-converter temperature will remain in the proper range. Importantly, the drive-by-wire control is able to finely match torque in 6-cylinder and 3-cylinder combustion modes, making the transition between the two virtually unnoticeable.

Direct Injection System
Conventional engines using multi-port fuel injection mix fuel and air before they enter the combustion chamber. With direct injection, fuel is injected directly into each combustion chamber. This allows for better combustion and overall efficiency.

The RLX 3.5-liter V6 features a compact, high-pressure, direct-injection pump that allows both high fuel flow and pulsation suppression, while variable pressure control optimizes injector operation. A multi-hole injector delivers fuel directly into each cylinder (not to the intake port, as in conventional port fuel injection designs).

The multi-hole injectors can create the ideal stoichiometric fuel/air mixture in the cylinders for good emissions control. Theoretically, a stoichiometric mixture has just enough air to completely burn the available fuel.

Based on the operating conditions, the direct-injection system alters its function for best performance. Upon cold engine startup, fuel is injected into the cylinders on the compression stroke. This creates a weak stratified charge effect that improves engine start-up and reduces exhaust emissions before normal operating temperature is reached.

Once the engine is fully warm for maximum power and fuel efficiency, fuel is injected during the intake stroke. This helps create a more homogeneous fuel/air mix in the cylinder that is aided by the high-tumble intake port design. This improves volumetric efficiency, and the cooling effect of the incoming fuel improves anti-knock performance.

Active Control Engine Mounts and Active Sound Control
A powerful 28-volt Active Control Engine Mount system (ACM) is used to minimize the effects of engine vibration as the VCM system switches cylinders on and off. The 28-volt ACM is a key factor in the VCM's broad range of operation in the RLX. Sensors alert the Electronic Control Unit (ECU) to direct ACM actuators positioned at the front and rear of the engine to cancel engine vibration. In the cabin of the RLX, an Active Sound Control system further reduces low frequency sound relating to the function of the VCM system.

Drive-by-Wire Throttle System
The RLX doesn't use a conventional throttle cable, but instead has smart electronics that "connect" the throttle pedal to a throttle valve inside the throttle-body. The result is less under hood clutter and lower weight, as well as quicker and more accurate throttle actuation. Plus, specially programmed "gain" between the throttle pedal and engine offers improved drivability and optimized engine response to suit specific driving conditions.

Acura's Drive-by-Wire throttle system establishes the current driving conditions by monitoring throttle pedal position, throttle valve position, engine speed (rpm) and road speed. This information is used to define the throttle control sensitivity that gives the RLX's throttle pedal a predictable and responsive feel. There are two different throttle profiles available in the RLX. When the transmission is in "D"(Drive) the drive-by-wire system uses the normal profile. When the Sport mode is engaged by pressing the Sport button located near the shift lever, the system changes the throttle map to increase throttle opening relative to accelerator pedal position to enhance response feel.

Direct Ignition and Detonation/Knock Control
The RLX's Power Control Module (PCM) monitors engine functions to determine the best ignition spark timing. An engine block-mounted acoustic detonation/knock sensor "listens" to the engine and, based on this input, the PCM can retard the ignition timing to prevent potentially damaging detonation. The 3.5L V6 has an ignition coil unit for each cylinder that is positioned above each spark plug's access bore.

Close-Coupled Catalysts and Variable Flow Exhaust System
The exhaust manifolds of the 3.5L V6 are cast directly into the aluminum cylinder heads to reduce weight, decrease parts count, and create more under hood space. The result of this casting design is that the two primary catalytic converters are positioned much closer to the combustion chambers. High-efficiency next-generation precious metal catalytic converters are mounted directly to the exhaust port of each cylinder head to enable extremely rapid converter "light-off"after the engine starts. A significant weight savings is realized by eliminating traditional exhaust manifolds.

Downstream of the close-coupled catalytic converters, a hydroformed 2-into-1 collector pipe carries exhaust gases to a secondary catalytic converter located under the passenger cabin floorboard. This high-flow secondary catalytic converter has a large inlet and outlet to enhance exhaust flow. To balance the engine's need for quiet operation at low rpm and higher flow at high rpm, the RLX's dual exhaust system incorporates a variable flow rate feature. Pressure-operated exhaust valves in each silencer are closed in normal operation, reducing exhaust noise by as much as 8 dB. When the driver demands more performance from the RLX, rising exhaust gas pressure opens both valves. The additional exhaust flow ads five horsepower to the engine's peak output.

 

Emissions Control
The 2018 RLX P-AWS meets the tough CARB LEV3 ULEV125 emissions standards; the 2018 RLX Sport Hybrid utilizes a higher amount of precious metals in its catalysts to meet CARB LEV3 SULEV30 emissions standards.

A number of advanced technologies are factors in the emissions performance. The unique cylinder head-mounted close-coupled catalytic converters light off more quickly after engine start up, and a 32-bit RISC microprocessor within the powertrain control module (PCM) boosts computing power to improve the precision of spark and fuel delivery.

To further improve emissions compliance, the 3.5L V6 makes use of an after-cat design exhaust gas recirculation (EGR) system that allows cleaner, cooler EGR gas to be fed back into the intake system. An EGR system, especially one that delivers a cleaner/cooler charge, reduces pumping loss for better fuel efficiency.

Push-Button Start System
To ensure consistent starting, the RLX has a one-touch Push Button start system that maintains starter engagement until the engine starts. Should the driver release the Start button before the engine starts, the system will start the vehicle.

Noise & Vibration Control
With its 60-degree V-angle and compact, rigid and lightweight die-cast aluminum cylinder block assembly, the 3.5L V6 powerplant is exceptionally smooth during operation. Other factors that help reduce engine noise and vibration are a rigid forged-steel crankshaft, die-cast accessory mounts, and a stiff cast-aluminum oil pan that reduces cylinder block flex.

100,000 Mile Tune-up Intervals
The RLX's 3.5L V6 requires no scheduled maintenance for 100,000+/- miles or more, other than periodic inspections and normal fluid and filter replacements. The first tune-up includes water pump inspection, valve adjustment, replacement of the camshaft timing belt, and the installation of new spark plugs.

Maintenance Minder™ System
To eliminate unnecessary service stops while ensuring that the vehicle is properly maintained, the RLX has a Maintenance Minder™ system that continually monitors the vehicle's operating condition. When maintenance is required, the driver is alerted via a message on the Multi-Information Display (MID).

The Maintenance Minder™ system monitors operating conditions such as oil and coolant temperature along with engine speed to determine the proper service intervals. Depending on operating conditions, oil change intervals can be extended to a maximum of 10,000 miles, potentially sparing the owner considerable expenditures and inconvenience over the life of the vehicle. The owner-resettable system 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 avoid driver distraction while the vehicle is being operated, maintenance alerts are presented on the MID when the ignition is first turned on.

Sport Hybrid Super Handling All-Wheel Drive (SH-AWD)
The RLX Sport Hybrid was the first production vehicle to employ an electric version of Super Handling All-Wheel Drive (SH-AWD), technology that later appeared in the NSX supercar and the MDX Sport Hybrid. Mechanical versions of SH-AWD have the ability to vary the amount of power sent to the rear axle, and to also vary rear power distribution between the left and right rear wheels via a longitudinally mounted drive shaft and rear differential with twin electronically controlled clutch packs.

In the RLX Sport Hybrid, the driveshaft and rear differential of a conventional all-wheel drive system is eliminated, replaced by twin 27-kilowatt (36-horsepower) electric motors that independently drive the left and right rear wheels. Each motor can also capture regenerative braking energy and apply negative (regenerative braking) torque to further enhance cornering capability.

Independent control of torque at all four wheels is a key feature of SH-AWD and its ability to enhance both dynamic handling and all-weather traction. When cornering, more positive (drive) torque is applied to the outside rear wheel, while negative (regenerative braking) torque can be applied to the inside rear wheel. This torque differential creates a yaw moment, producing sharper turn-in, more linear cornering, enhanced traceability and improved steering response with reduced understeer tendencies. In addition, since the system doesn’t rely on the gasoline engine for torque, electric SH-AWD can create a larger torque difference between the left and right rear wheels, even during small throttle applications, at low engine speeds, or even during deceleration (such as lifting throttle mid-corner). This substantially magnifies the positive handling benefits of SH-AWD across a much wider range of driving conditions. New for 2018, torque distribution enhancements contribute to enhanced response linearity and stability.

Power Drive Unit (PDU)
The Power Drive Unit, packaged in the center of the vehicle beneath the center console, dictates the power management strategy of the RLX Sport Hybrid SH-AWD system, including motor power and battery recharge.

Intelligent Power Unit (IPU)
The Intelligent Power Unit is positioned above the Twin Motor Unit, behind the rear seatback. The IPU contains the hybrid system's lithium-ion battery, 12-volt DC/DC converter, junction board, and Electronic Control Units (ECU) for the motors and the battery. The IPU is air-cooled via an integrated fan unit that draws air from inside the vehicle cabin via an intake duct located beneath the rear seats.

New Lithium-Ion Battery
The RLX Sport Hybrid's new advanced 72-cell lithium-ion battery is 8.2 lbs. lighter than the previous generation battery.

Front Electric Motor
A single 35-kilowatt (47-horsepower) electric motor is integrated with the 7-speed DCT. The motor's operating temperature is optimized by a temperature-controlled flow of Automatic Transmission Fluid (ATF) through the motor housing. By tightly controlling the motor temperature, the motor's constantly available rated output (both drive and regeneration) can be significantly improved.

Twin Motor Unit (TMU)
The RLX Sport Hybrid's Twin Motor Unit (TMU) is located between the rear wheels, where a differential on a conventional all-wheel-drive vehicle is typically mounted. Inside its die-cast aluminum housing are two electric motors positioned back-to-back. Each 27-kilowatt (36-horsepower) motor powers a single rear wheel and can also apply negative torque to the same wheel. A clutch allows each motor to be decoupled from its wheel in certain operating situations to improve efficiency.

Electrically Powered Air Conditioning Compressor
Since the RLX Sport Hybrid engine has an idle-stop feature, it is equipped with an electrically powered air conditioning compressor. This allows continuous air conditioning operation even when the gasoline engine is shut off.

Transmissions
Two different transmissions are available in the 2018 RLX. The RLX P-AWS has an all-new Acura-first 10-speed automatic transmission. The RLX Sport Hybrid has a standard 7-Speed Dual-Clutch Transmission (DCT).

10-Speed Automatic Transmission
The RLX P-AWS has a standard new 10-speed automatic transmission. Engineered for high efficiency with low internal inertia and an exceptionally wide ratio range, the 10-speed automatic maximizes the RLX's performance and fuel efficiency. The 10-speed is 22 lbs. lighter and has a 68 percent wider overall ratio range, with a 43 percent lower first gear and a 17 percent taller top gear, compared to the previous generation RLX's 6-speed automatic.

The 10AT is designed to be lightweight and compact. It features four planetary gear sets that work together to provide an exceptionally wide gear ratio spread. Its overall ratio spread of 10.15:1 compares with the 6.04:1 spread on the previous generation RLX 6-speed, a 68-percent increase. The 10AT also has substantially faster upshift and downshift performance than the previous 6-speed transmission. For greater responsiveness, the 10AT is capable of 4-gear direct downshifts – from 10th gear to 6th, or from 7th to 3rd.

To maximize fuel efficiency and minimize interior noise, the transmission's 10th gear is exceptionally tall, resulting in quiet and relaxed cruising rpm.

7-Speed Dual-Clutch Transmission (DCT)
To maximize performance and fuel efficiency, the RLX Sport Hybrid has a standard 7-Speed Dual-Clutch Transmission (DCT). In the 7-speed DCT, one clutch controls the odd gears while the other clutch controls the even gears. This arrangement allows gear
changes with a much smaller interruption in power to the wheels, resulting in millisecond-quick shifts. Compared to a conventional manual transmission, the operation of the clutches and shifting mechanisms are electronically controlled, eliminating the need for a clutch pedal or shift lever. Compared to a conventional automatic, the torque converter and its mechanical inefficiencies are also eliminated.

Common Transmission Features

Electronic Gear Selector
In the RLX Sport Hybrid, and for the first time ever in the non-Hybrid RLX, the conventional console-mounted shift lever is replaced with an Electronic Gear Selector. Park, Neutral and Drive are selected with the push of a button. Reverse is selected by pulling back a dedicated switch. Indicator lights near the buttons indicate the mode selected. As an added safety feature, if the vehicle is brought to a stop in Drive, the system will automatically select Park if the driver's seatbelt is unbuckled and the driver's door is opened.

Automatic Modes
Both RLX transmissions can be operated in two different fully automatic modes. The D (or "Drive") mode is ideal for most driving situations, and combines fuel efficiency with smooth operation and responsive power when needed. The SPORT mode (selected with the SPORT button near the transmission controls) is meant for more demanding driving, and features more aggressive shift mapping to keep engine rpm higher for greater acceleration and pulling power.

When in the D mode (optimized for normal driving), the transmission incorporates an advanced Grade Logic Control System, Shift Hold Control and Cornering G Shift Control – all of which reduce unwanted shifting and gear hunting. The result is smart transmission operation that optimizes fuel efficiency and keeps the transmission in the appropriate gear for driving conditions, generating excellent performance and smooth operation.

While ascending or descending hills, Grade Logic Control alters the transmission's shift schedule to reduce shift frequency and improve speed control. The transmission ECU continually measures throttle position, vehicle speed and acceleration/deceleration to determine when the vehicle is on a hill. The shift schedule is then adjusted – during ascents to hold the transmission in lower gears to boost climbing power, and during descents to provide greater engine braking.

Shift Hold Control keeps the transmission in its current (lower) gear ratio during aggressive driving, as in the case of decelerating at a corner entry. Shift Hold Control leaves the chassis undisturbed by eliminating excess shifting and ensures that power will be immediately available (without a downshift) at the corner exit. When the system detects a sufficient speed differential between the rear wheels (10AT), or sufficient lateral acceleration (7DCT), it will suppress any unwanted upshifts. This prevents the transmission from upshifting during a corner, which could upset the chassis balance thus requiring downshifting again at the corner exit when the throttle is applied.

Paddle Shifters
Both available RLX transmissions feature a steering wheel-mounted paddle shifter system that lets the driver take manual control of transmission gear selection. Particularly useful in mountainous terrain or during aggressive driving, the paddles give the driver greater control over transmission operation. On long downgrades, the driver can command downshifts with the paddles that allow engine braking to be used to reduce the load on the brakes and help control the RLX's downhill speed.

Paddle Shifter Operation in Drive Mode
While in Drive mode, special transmission logic programming allows the use of the steering-wheel-mounted paddle shifters. When the driver operates the paddle shifters, the transmission responds to the driver's shift command and then returns to its normal fully automatic mode if further paddle shift inputs are not made within a few seconds depending upon driving conditions. Long holds of the upshift paddle also allows return to automatic mode. This special logic makes it easy for the driver to command a quick downshift without leaving the convenience of Drive mode.

Paddle Shifter Operation in Sequential Mode
By pressing the SPORT button, Sequential mode is engaged. This mode offers automatic operation with more aggressive shift mapping. A pull on either of the paddle shifters places the transmission in manual mode until another mode of operation is selected. A digital display in the instrument cluster indicates which gear the transmission is in.

In the 7DCT, a double-kick-down feature lets the driver command a sporty double downshift. By pulling on the left downshift paddle twice in rapid succession, the transmission will drop directly to the chosen lower gear ratio. With both transmissions, the Drive-by-Wire™ throttle system also creates a "blip" of the throttle to help match gear speeds while downshifting.

To prevent harm to the powertrain when the transmission is paddle shifted by the driver (including during -down shifts), the system will inhibit potentially damaging shifts, and upshift if needed to avoid over-revving. As an added safety measure, the Electronic Control Unit (ECU) can also cut off fuel to the engine to prevent over-revving. On downshifts, the transmission will not execute a driver command that will over-rev the engine.

For improved stop-and-go performance and to help prevent "lugging" the engine, the RLX will automatically downshift to an appropriate gear even though the transmission has been left in a higher gear, as the vehicle comes to a stop.

Grade Logic Control
While traveling up or down hills, Grade Logic Control alters the transmission's shift schedule to reduce shift frequency and improve speed control. A shift map in the transmission computer continually measures throttle position, vehicle speed and acceleration/deceleration, and then determines when the vehicle is on a hill. The shift schedule is then adjusted to hold the transmission in lower gears to boost climbing power or to provide engine braking when traveling downhill.

Shift Hold Control
Shift Hold Control logic keeps the transmission in its current (lower) gear ratio when aggressive driving is detected, as in the case of decelerating at a corner entry. Shift Hold Control leaves the chassis undisturbed by excess shifting and ensures that power will be immediately available (without a downshift) at the corner exit.

Cooperative Control
Both shift performance and smoothness are improved by cooperative control between the Drive-by-Wire™ throttle system and the electronically controlled transmission. The engine is throttled by the engine management system during upshifts and downshifts so the function of the engine and transmission can be closely choreographed for faster, smoother shifting. As a result, the peak g-forces (or "shift shock") are reduced significantly during upshifts and downshifts.


Transmission Ratio Comparison

 

2018 RLX P-AWS
(10-speed AT)

2018 RLX Sport Hybrid SH-AWD
(7-speed DCT)

1st

5.246

4.396

2nd

3.271

2.753

3rd

2.185

2.034

4th

1.597

1.546

5th

1.304

1.143

6th

1.000

0.842

7th

0.782

0.623

8th

0.653

-

9th

0.581

-

10th

0.517

-

Reverse

3.974

3.663

Final

3.613

3.579

Ratio Range

10.15:1

7.06:1