Direct4 is an exclusive new all-wheel drive control technology for next-generation Lexus Electrified vehicles. Making its production debut in the all-electric Lexus RZ 450e, this innovative system was engineered to constantly adjust the balance of torque and braking effort that is delivered between all four wheels.
Improvements in safety and performance were among the primary targets for this new technology. Yet the overriding intention for the development team was to deliver an experience in which human senses react positively: a driving feel that is natural, confidence-inspiring, even exhilarating. How does it achieve this?
How does Direct4 work?
Direct4 is an intelligent all-wheel drive system that constantly monitors and controls the amount of drive torque and braking force that is delivered between and across the vehicle’s two axles.
A key element of the torque distribution system is the e-Axle, a drive unit that combines a high-torque electric motor, ECU and transaxle in one compact, modular package. The unit is located between the wheels and configured so that the motor and transaxle are on the same plane to optimise drive force distribution more instantaneously.
As illustrated in the above video, Direct4 has the ability to adjust the front-to-rear balance according to prevailing conditions and driver input. The breadth of this flexibility can be anywhere between 100:0 and 20:80 and is delivered in a matter of milliseconds – more precisely than any mechanical system could.
For example, when pulling away, the system controls the ratio from between 60:40 and 40:60 in order to suppress front-end lift while maintaining a direct acceleration feel. When cornering, the system uses information such as vehicle speed and steering angle to determine drive force distribution and secure handling stability. Drive force is weighted towards the front axle (70:30 to 50:50) at the start of a turn, then progressively becomes more rear-biased (50:50 to 20:80) when exiting the corner, giving excellent traction and maintaining overall stability.
The benefits of Direct4 are experienced in the following driving conditions:
- Standing start: drive force is delivered to all four wheels
- Straight line driving: vehicle remains steady at all times
- Entering a bend: change of direction is smooth
- Steering through a bend: steering provides excellent feedback
- Accelerating out of a bend: easy for the driver to trace a faithful line
- Exiting a bend: confident, direct acceleration
Direct4 is highly responsive and operates intuitively, giving the driver a genuine sense of connection with the vehicle. Moreover, it provides an ideal balance of predictability and excitement, with powerful, linear acceleration and exhilarating cornering. At the same time, the system is engineered for quietness and comfort, true to the core quality of Lexus vehicles.
Which Lexus models have it?
Currently, two models are equipped with Direct4: the Lexus RZ 450e and the Lexus RX 500h. As an all-electric model, the RZ 450e features an e-Axle front and rear, while the RX 500h is a hybrid model and therefore uses a single e-Axle on the rear.