DIRECT4: how Lexus’s torque control technology delivers driving rewards and comfort in the new all-electric RZ 450e

Driving enjoyment and passenger comfort are both enhanced in the Lexus RZ 450e by the car’s DIRECT4 intelligent all-wheel drive control system. This exclusive Lexus technology, making its debut on the battery electric RZ, which is due for launch later this year. The system automatically manages drive force distribution between the front and rear e-Axles within milliseconds, in response to driving conditions and the driver’s inputs.  

DIRECT4 continually provides optimal drive force balance between front and rear through independent control of the front and rear e-Axles. Sensors constantly monitor factors such as 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 per cent or 100 per cent to zero and anything in between, in milliseconds, faster than any mechanical system.  

DIRECT4 adjusts the balance of front/rear drive torque to achieve ideal performance. Details of the distribution in different driving situations are shown in the table below. 

 

Driving situation

 

Normal torque distribution (front:rear) 

Potential torque distribution (front:rear) 

Aim 

Starting off 

60:40 

20:80 

Drive torque transferred to the rear to enhance traction and stability. 

Straight-line driving 

70:30 

40:60 

Torque distributed to optimise straight-line stability and improve efficiency. 

Turning 

75:25 

20:80 

More torque directed to the rear wheels to achieve better traction in low-grip conditions and confident line-tracing and good acceleration when exiting a bend. 

Driving in Range mode 

0:100 

50:50 

In Range mode with low torque driving only the rear motor is used to improve operating efficiency 

The system also automatically adjusts the braking force on all four wheels and improves the energy efficiency of Lexus’s first purpose-designed BEV.  

RZ Chief Engineer Takashi Watanabe took inspiration from the animal kingdom when working to define the poise and agility he sought for the new SUV. Specifically, he was fascinated by how the cheetah – the world’s fastest land animal – moves its body as it sprints and swerves in pursuit of prey, while keeping its head stable and its eye-line fixed. This inspired Lexus’s engineers to think of new ways to control the RZ’s body posture, and with DIRECT4 they were able to give the vehicle exceptional pitch control. The extent to which the vehicle tilts backwards under acceleration and forwards under braking is limited, reducing the corresponding movements of occupants’ heads. This gives the driver a more stable sightline and enhances passenger comfort, especially in the rear seats. 

DIRECT4 provides 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. 

*Article Source www.lexus.co.uk