Lexus NX compact utility arrives in North America
7 July 2014
|2015 Lexus NX 300h. Click to enlarge.|
Lexus has introduced the new Lexus NX compact utility, first unveiled in Beijing (earlier post) to North America. The 2015 Lexus NX debuts in two versions, the NX 200t with a turbocharged 2.0-liter four-cylinder engine and the NX 300h hybrid with 2.5-liter Atkinson-cycle gasoline engine, which brings the brand’s number of hybrid offerings to six—the most among luxury brands.
Among the features of the hybrid is a new transmission with a kick-down function. Further, the hybrid battery pack is split into two separate pods for better weight distribution, with the additional benefit of more efficient use of cabin space. Both NX models offer their own version of pro-active all-weather drive (AWD). The new Lexus NX features numerous other firsts in a Lexus, among them:
The all-new 2.0-liter turbocharged gasoline engine has a combination water-cooled cylinder head, integrated exhaust manifold and twin-scroll turbocharger.
The front axle adopts a pre-load differential to control differential torque. It assists turning on slippery roads and straight-line stability at high speed.
Standard energy-efficient LED headlights and taillights.
Touch-sensitive interior lamp switches in the headliner.
NX 200t: new turbocharged engine. Lexus created an all-new engine architecture for its first turbo. The 2.0-liter turbocharged port and direct-injection engine uses an advanced valve control system to switch between Atkinson cycle and Otto cycle operation to optimize performance and fuel efficiency.
To minimize turbo lag, the four-into-two exhaust manifold system pairs cylinders according to their expansion or compression stroke to reduce pumping losses and eliminate exhaust gas interference. This results in improved acceleration response and wide torque band. The turbo engine produces 235 hp (1756 kW) at 5,600 rpm with 258 lb-ft (350) of torque from 1,650-4,000 rpm and up to 17 psi of boost at wide open throttle. A balance shaft enhances smoothness.
The combination of direct fuel injection and additional port fuel injectors, as used on some other Lexus models, ensures ample power and crisp responsiveness at all engine speeds.
Combining the cylinder head, exhaust manifold and intercooler with variable wastegate control enhances low speed torque fuel economy. Active wastegate control minimizes pumping losses by reducing backpressure during low engine load. The water-cooled intercooler, mounted directly to the engine, provides strong advantages in acceleration. A dual exhaust system reduces backpressure and noise.
The D-4S fuel injection system provides the optimum mixture to realize the highly efficient rapid combustion.
To keep the engine oil clean, the intake system creates a syphon which draws carbon vapors away from the crankcase allowing for 10,000 miles between oil changes similar to aspirated engines.
Dual Variable Valve Timing with intelligence (VVT-iW) optimizes torque throughout the engine speed range and allows the engine to start in the Otto cycle and then run in the more fuel efficient Atkinson cycle. The late intake valve closing of the Atkinson cycle reduces pumping losses and boosts fuel economy.
The turbo engine was bench-tested for more than 10,000 hours before extensive on-road testing, covering more than 600,000 miles, began.
New six-speed transmission. An all-new sequential six-speed automatic transmission networks with the turbo engine to achieve an ideal level of boost pressure for performance and fuel economy. Torque-demand control logic calculates required engine torque and maximizes it, delivering quick response and exhilarating acceleration feel with good fuel efficiency.
The G-force Artificial Intelligence (G-AI) system is also adopted for more spirited driving. G-AI automatically selects the optimum gear and downshift pattern in response to G force.
NX300h: Hybrid with a kickdown. The NX 300h shares the sporty persona of its turbocharged sibling while delivering higher fuel efficiency. The Lexus Hybrid Drive system can be matched to 2WD or the Lexus E-Four AWD system.
Lexus tuned the 2AR-FXE 2.5-liter gasoline engine especially for use in the 2015 NX 300h. Enhancements include a water-to-oil cooler for the electric drive motor and a revised front drive reduction ratio, improving fuel economy and hill climbing.
The new P314 transmission provides a kick-down function for greater acceleration performance. The transmission consists of an electric motor generator and an electric drive motor linked by a double set of planetary gears. The planetary gearset simultaneously fulfills three roles:
as a power split device between the generator and the front wheels;
as a reduction gear for the electric motor; and,
when both work together, as an electronically controlled continuously variable transmission (CVT).
The transmission offers sequential shift which allows maximum power to be delivered on demand and increases engine braking when decelerating.
The NX 300h employs Lexus’ electronically controlled braking system known as ECB-R to provide cooperative control of stopping power and regenerative braking while saving on vehicle weight.
NX 300h: driving dynamics. New HV control software minimizes engine flare during acceleration and increases the sensation of linear acceleration. Engine speed is increased relative to the accelerator pedal angle. The NX 300h adjusts to the target engine speed and to the G force applied to the vehicle, providing a more natural acceleration feeling, without excessive adjustment to the engine speed and gear ratio. Drivers can shift themselves with the sequential Shiftmatic feature.
Drivers can optimize fuel economy using Eco or Normal modes in Drive Mode Select, or use Shiftmatic in Sport mode to better enjoy a winding road.
The NX Hybrid has sprung weight damping control to reduce pitching on uneven road surfaces and increase ride comfort and stability. The system controls motor torque and adds power to the opposite direction to help minimize body movement. The rear motor (MGR) helps the starting off performance and stability on slippery roads.
Hybrid battery pack. The hybrid battery pack is split into two modules, each weighing 44 lbs (20 kg) and located on each side of the rear seat, improving space efficiency and also center of gravity for enhanced car control. The battery pack is one of the lightest among Lexus hybrids.
Package efficiency improvements include downsizing the Power Control Unit (PCU) with a double-sided inverter cooling system. The PCU inverter boosts direct current (DC) voltage from the HV battery and converts it to alternating current (AC) to drive the electric traction motor and, where applicable, the rear-drive E-Four electric motor. It also converts AC from the generator to DC for storage in the hybrid battery.
The PCU also includes a DC-DC converter to provide 12-volt power for vehicle ancillaries, including the lights and audio system. The DC-DC converter saves fuel, because the gasoline engine does not have to drive a separate alternator. The entire 2WD PCU is installed in the engine compartment. In the AWD model, the inverter and DC-DC converter are located at the rear of the vehicle.
NVH. NX 300h’s engine mounts are tuned to suppress start-up vibration from the gasoline engine, contributing to ride comfort. The mounts allow for only one-tenth of the conventional deviation from the engine’s normal axis away from its center of gravity—the cause of vibration.
Like other Lexus Hybrids, the NX 300h can be very, very quiet. For example, it uses the electric motor exclusively when reversing. A continuous sound emitted from the vehicle proximity notification speaker mounted near the front bumper alerts pedestrians and cyclists of the approaching vehicle.
Drivelines. In the NX 200t, the available Dynamic Torque Control AWD system can instantly vary front and rear torque split between 50:50 and 100:0 for optimum traction and fuel economy. The NX 300h hybrid offers the Lexus E-Four AWD system with an electric motor to drive the rear axle when required.
In both models, a pre-loaded front differential (and yaw rate feedback control on AWD versions) ensures optimum grip, control and agility. The differential uses a plate spring between the side gear and side-gear washer to add pre-load, which limits torque split between the front wheels. Under light loads, and when there is a low speed difference between the left and right wheels during cornering, the pre-loaded differential ensures straight-line stability and acceleration performance. At higher speeds, it operates as an open differential.
NX 200t: Dynamic Torque Control AWD. The NX 200t with all-weather drive introduces Dynamic Torque Control AWD to provide maximum traction and cornering stability. The system continuously controls torque transfer between the front and rear wheels, using sensors for vehicle speed, steering angle, steering speed, throttle angle and yaw rate.
To conserve fuel, the system uses front-wheel drive during normal cruising. When required, it automatically engages AWD through an electromagnetically controlled coupling in the rear differential housing, directing up to 50% of available torque to the rear wheels. When the driver makes too wide of a turn, the Dynamic Torque Control AWD helps bring the vehicle back to the intended drive line.
NX 300h Hybrid: E-Four AWD. The efficient Lexus E-Four proactive all-weather drive system in NX 300h hybrid uses an electric motor to drive the rear axle, while the front axle is propelled by gasoline or electric power, or a mixture of both. The E-Four system varies torque distribution to the rear wheels, depending on driving dynamics and road conditions, and provides some rear-wheel torque at start-off to minimize chance of wheel-spin under acceleration and on slippery road surfaces.
E-Four saves energy and fuel, because the vehicle only uses all-wheel drive when needed. When the system detects loss of traction of the front wheels it reduces the electricity supply to the traction motor in the transaxle and increases supply to the rear-axle motor. The rear motor acts as a generator when the NX is in regenerative braking mode, increasing the amount of kinetic energy recovered.
The Lexus E-Four AWD system has situation-specific control features similar to Dynamic Torque Control proactive AWD in the NX 200t AWD model, including a yaw-rate control system for enhanced driving performance.
Drive Mode Select. The Drive Mode Select dial on the center console lets the NX driver tailor the vehicle’s responses and driving feel to suit driving conditions or just the driver’s mood. The system adjusts parameters for multiple systems, including throttle response and the power steering assist curve.
The default setting is Normal. There is also ECO, for even more fuel-efficient driving, and Sport. The NX 300h has a button adjacent to the dial to select EV mode.
Onboard technology. The 2015 NX is the first Lexus to offer an available Qi wireless charging tray inside the console box. If you’ve got a compatible smartphone or other device, just placing it in the tray will recharge its battery.
The multi-media system, accessed through a high-resolution seven-inch screen, provides a multitude of capabilities and also offers the Navigation upgrade. The optional Navigation system provides up to date and predictive traffic information, including detour preview, ETA calculation and low-fuel coordination with nearby fuel stations. Navigation also includes the subscription-free Lexus Enform App Suite and features 3D and bird’s eye map views with 3D building views. The available Navigation also adds a second USB outlet.
The NX also offers Siri Eyes Free Mode, compatible with the iPhone 4S and iPhone 5. Siri lets you call contacts, select and play music from iTunes, get turn-by-turn navigation through Siri and Apple maps, and more.
Lexus Enform Remote (subscription required), the latest addition to the Lexus Enform family of connected services, allows the owner to remotely view and control certain vehicle features using a mobile app for iOS and Android devices. Key features include remote door lock/unlock; remote stop/start for the engine and climate control; vehicle finder, guest driver monitor and more.
Lexus Enform Safety Connect is the foundation for all Lexus Enform products and includes an Emergency Assistance Button (SOS), Roadside Assistance, Automatic Collision Notification, and Stolen Vehicle Notification.
In addition to maintaining a constant speed, the available Dynamic Radar Cruise Control can also maintain a vehicle-to-vehicle distance. The system’s All Speed Following Function can even stop the NX when the vehicle ahead stops at speeds up to 37 mph (60 km/h).
Safety. Frontal and side collision protection measures include the use of high tensile steel up to 142,000 psi in key areas, including the center-pillar hinge reinforcement, outer rockers and roof crossmembers. In a collision, energy from a side impact is transmitted to the floor through a structure of cross-members built into the rocker beneath the center B-pillar. The rear impact structure disperses offset collision energy to the main chassis members on both sides of the vehicle.
A comprehensive roof impact-resistance structure disperses load when the roof is impacted, minimizing cabin distortion. The structure includes front pillar reinforcement and high strength steel reinforcements for the center pillar, as well as reinforcement around the seatbelt anchor and front header.
Lexus Whiplash-Injury Lessening front seats are fitted to all models, and the NX has energy-absorbing structures in the pillars and roof headliner. There are impact-absorbing pads in the front and rear door trim adjacent to the occupant’s lumbar region.
The Lexus NX models have eight SRS airbags, including a dual stage driver’s airbag and knee airbag, dual-stage and dual-chamber front passenger airbag, front side airbags and full-length side curtain airbags, and offer the available Lexus Pre-Collision Safety System (PCS).
Available Lane Departure Alert warns the driver when it determines that the vehicle is about to veer from a traffic lane. A camera mounted to the windshield recognizes lane markings. It sounds a warning and provides a visual representation on the Multi-Information Display screen if the vehicle is veering from its lane. The system works in rain and on roads where the lane is marked on one side only.
Intelligent High-beam uses the same windshield-mounted camera. When the driver turns the high beam on, it will switch to low beam to help prevent blinding other drivers and restore high beam when there are no vehicles ahead are detected. The system can also dim the high beams when it detects bright streetlights. When conditions permit, the high beams will automatically resume.
Pre Collision System (PCS) uses the all-speed Adaptive Cruise Control system’s millimeter-wavelength radar sensor to detect vehicles and other obstacles. A buzzer and a light help warn the driver of impending collision. The system can increase the driver’s braking effort, and activate Pre-Collision Brake if the driver doesn’t apply the brake. The system can also bring the NX to a full stop. Pre-Collision Brake deceleration works from a maximum speed of 37 mph.
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