The Lexus NX 300h powertrain

The NX 300h introduces the driving experience of Lexus Hybrid Drive to the mid-sized premium SUV segment for the first time. The system combines a Lexus 2.5l Atkinson cycle engine, generator, motor and battery with a Hybrid Vehicle control unit developed specially for the NX.New LEXUS NX 300h

The powertrain delivers a total system output of 145 kW (193 hp), whilst returning an average fuel consumption of 5.0 l/100km and generating CO2 emissions of 116 g/km over the regulatory NEDC driving cycle.

Fine-tuning of the 2.5-liter engine have resulted in greater responsiveness and improved fuel efficiency. Enhancements include a water-to-oil cooler for the electric drive motor for improved motor cooling and a revised front drive reduction ratio, improving fuel economy and hill climbing.

A newly developed HV trans-axle provides a kick-down function for better acceleration. The new trans-axle consists of an electric motor generator and an electric drive motor linked by a double set of planetary gears.

The planetary gear set 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 constant velocity transmission. The trans-axle offers sequential shift which allows maximum power to be delivered on call and increases engine braking.

The hybrid power plant can be matched to 2WD or the Lexus E-Four electric motor-powered AWD system.LEXUS NX 300h front view

Acceleration feel

Newly developed HV control software which minimizes engine flare during acceleration increases the sensation of linear acceleration. Engine speed has been increased relative to the accelerator pedal angle, creating a downshift-like feeling. The NX 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.

The sequential Shiftmatic feature meets customer demand for a shifting feel similar to that of a manual gearbox.

New engine mounts

The NX 300h’s engine mounts are tuned to suppress start-up vibration from the petrol engine, reducing fuel consumption, and contributing to ride comfort. The mounts allow for 10% of the conventional deviation from the engine’s normal axis away from its center of gravity – the cause of vibration.

The offset between the axis and the center of gravity was reduced by a matter of millimeters by adjusting the engine mounts. This detailed work has also had a positive influence on handling.

Technical characteristics of the NX 300h powertrain

Type, Materials In-line 4-cylinder aluminum block and heads
Designation 2AR-FXE
Valvetrain DOHC 16-valve with Atkinson cycle Dual VVT-i
Displacement 2.5 liter in-line 4-cylinder w. Atkinson cycle; 2,494 cm3
Bore x Stroke 90.0 mm x 98.0 mm
Compression Ratio 12.5:1
Horsepower 114 kW / 155 DIN hp @ 5,700 rpm
Torque 210 Nm @ 4,200-4,400 rpm
Fuel System Electronic Fuel Injection
Fuel Requirement 91-octane or higher unleaded
Emission Certification Euro6
0-100 km/h Acceleration 9.2 sec. (FWD/AWD)
80-120 km/h Acceleration 7.0 sec. (FWD) / 7.3 sec. (AWD)
Max. Speed 180 km/h
Fuel Consumption FWD AWD
– Urban 5.0-5.3 l/100km 5.1-5.4 l/100km
– Extra Urban 5.0-5.2 l/100km 5.0-5.2 l/100km
– Combined 5.0-5.2 l/100km 5.1-5.3 l/100km
CO2 emissions
– Urban 117-123 g/km 118-125 g/km
– Extra Urban 115-120 g/km 116-121 g/km
– Combined 116-121 g/km 117-123 g/km
HYBRID SYSTEM Series/parallel system with petrol engine, high-voltage battery and electric motors
Total System Power 145 kW / 197 DIN hp
Front Motor- Motor Generator 1 (MG1)
Function Generator, charge the hybrid battery, engine starter
Type Permanent Magnet Motor
Max. voltage AC 650V
Front Motor- Motor Generator 2 (MG2)
Function Drives front wheels, regeneration during braking
Type Permanent Magnet Motor
Max. voltage AC 650V
Max. output 105 kW / 143 DIN hp
Rear Motor
Function Drives rear wheels, regeneration during braking
Type AC 650V
Max. voltage 50 kW / 68 DIN hp
Layout Front-engine full-time All-Wheel-Drive (AWD) or front-engine Front-Wheel Drive
Transmission Type Electronically Controlled Continuously Variable Transmission (ECVT) planetary gear unit for gear reduction and power splitting, electronic all-or front-wheel-drive control system
Designation P314
Differential Ratio 3.750 (FWD) / 3.542(AWD)
Source: Lexus

Romain’s opinion:

Lexus and Toyota have always been ahead when it comes to hybrid powertrains. This HV powertrain now equips most of the sold Lexus models, which means that it is recognized by the customer. What do you think is the roadmap for the future evolutions of this powertrain? Will the aim be to lower the cost or to further improve the fuel economy?

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