23 / 1 / 2023

HOW DIRECT4 ENHANCES LEXUS RZ DRIVING ENJOYMENT

  • Automatically variable torque distribution between front and rear e-Axles
  • Cheetah-inspired vehicle body control and posture
  • Delivering Confidence, Control, and Comfort with Lexus Driving Signature

Driving enjoyment and passenger comfort are both enhanced in the Lexus RZ by the car’s DIRECT4 intelligent all-wheel drive control system. This exclusive Lexus technology, which is introduced on the RZ, automatically adjusts driving force distribution between the front and rear e-Axles within milliseconds in response to driving conditions. DIRECT4 also automatically adjusts the braking force on all four wheels in accordance with ground contact load and improves this Battery Electric Vehicle’s energy efficiency.

When Chief Engineer Takashi Watanabe observed the world’s fastest animal, the cheetah, in action, he was fascinated by how the big cat’s body moves in all kinds of ways when it sprints and swerves in pursuit of prey, yet its head remains surprisingly stable, and its eye-line is unwavering. This inspired Lexus’ engineers to think of new ways to control the RZ’s body posture, and with DIRECT4 they were able to bestow the vehicle with exceptionally good pitch control. The extent to which the vehicle tilts backwards under acceleration and forwards under braking is now more limited, reducing the corresponding movements of occupants’ heads. This gives the driver a more stable sightline and significantly enhances passenger comfort, especially in the rear seats.

This inspiration from the cheetah also influenced the RZ’s exterior styling.

In addition to the greater control of vehicle body posture, and a reduction in sudden cabin movements for a smoother ride, the other benefits of DIRECT4 are powerful and smooth on-demand acceleration; excellent traction under acceleration and on slippery surfaces; better stability through corners; and reassuringly secure braking.  

Automatically variable torque distribution also enhances the precise, linear, natural-feeling responses to driver inputs. All these attributes strengthen the RZ’s core driving characteristics, represented by the “three C’s” that are the cornerstones of the Lexus Driving Signature: Confidence, Control, and Comfort.

DIRECT4 continually provides optimal drive force balance between front and rear by controlling each e-Axle independently. Sensors send information to the BEV ECU about wheel speed, longitudinal G, and steering angle. DIRECT4 responds to this information, to maximise traction and grip, almost instantly: front/rear torque bias can be adjusted from zero to 100% or 100% to zero and anything in between in milliseconds, faster than any mechanical system.

 

Torque is divided between the front and rear e-Axles according to driving conditions:

 

USUAL

(FR : RR)

UP TO

(FR : RR)

AIM
STARTING OFF

60 : 40

20 : 80

Torque transfer to rear to enhance traction and stability
STRAIGHT DRIVING

70 : 30

40 : 60

Torque transfer to optimise straight line stability and improve efficiency
TURNING

75 : 25

20 : 80

More torque to the rear to enhance traction in low friction situations.

During cornering, more torque to the rear to give confident line tracing and good acceleration feel when exiting the corner.

RANGE MODE

0 : 100

50 : 50

In low-torque driving, only the rear motor is used to maximise driving range.