Automotive Engineering - April 2023 - 18

Steer-by-wire stars on the new
LEXUS
RZ 450E
The 2023 RZ 450e has one motor each for front and rear axles,
both powered from the same central 71.4-kWh battery.
Lexus' first BEV arrives with innovative touches, dual-axle propulsion
and less-than-spectacular range.
by Chris Clonts
E
ven while Toyota was being criticized for its electrification
strategy and its pace in embracing BEVs, the company's engineers
were quietly prepping the Lexus brand's first EV, the
2023 RZ 450e crossover.
SAE Media recently drove the RZ and spoke with engineers about
its development at an event in Provence, France. While not underpowered,
with a total of 230kW (313 hp) available when both front
and rear motors are at peak output, some will question the vehicle's
below-average driving range.
The RZ's 71.4-kWh, 355V lithium-ion battery - developed by
Tokyo-based Prime Planet Energy & Solutions, a Toyota affiliate company
- has 96 cells, is sealed with urethane and cooled and heated
with circulating coolant. Lexus says the RZ's EPA-estimated driving
range is 220 miles (354 km) fitted with 18-inch wheels and 196 miles
(315 km) with 20-inch wheels. Charging from 0 to 100% with a Level
2 240V/ 32-amp charger takes 9.5 hours, the company claims. A
400-amp DC fast charger requires 30 minutes to go from 0 to 80%.
When asked about the range, engineers and officials had two
points. One, that the range is plenty for the RZ's strongest use case: a
two-vehicle household whose other car is an ICE or hybrid vehicle.
Why include more capacity than needed for day-to-day local use,
Toyota argues, when it would just increase cost and mass?
As an interesting hedge against range anxiety, Lexus will launch a
program called Lexus Reserve that allows RZ buyers 30 days of free
access to ICE or hybrid models during the first three years of ownership.
So, road tripping from the U.S. coasts to Yellowstone isn't out of
the question. Lexus also is partnering with ChargePoint and Qmerit
18 April 2023
to guide new owners on home-charger installation.
Besides, said Yushi Higashiyama, assistant chief engineer
for RZ performance, the design is locked in.
" The only way for this platform [called e-TNGA] to
have higher capacity is to make it longer, " he said
through a translator. Lexus' new CEO Koji Sato seemingly
has marked the RZ as a bridge project, saying a
next-generation BEV platform arrives around 2026.
Toyota and Lexus plan to release 28 new EVs by 2030.
The dual-motor nature of the RZ presents some interesting
challenges when talking about power distribution.
For instance, when engineers say that the vehicle's
Direct 4 AWD system can transfer 100% of drive
torque to the rear wheels, it comes with an asterisk.
Because there is no driveline connecting the front motor
(150 kW/201 hp) to the rear, it means that only the
80-kw (107-hp) motor is driving the rear wheels.
One can imagine a lack of power in situations that
would call for rear bias, such as spirited exits from
curves and around corners. But that's not the case.
While nobody is likely to take the RZ to the track,
there is plenty of power available, in any combination,
to make driving the RZ enjoyable. Lexus claims the RZ
can accelerate to 60 mph (96.5 km/h) in five seconds.
Delivering power to the ground are high-torque eAxles
with three-point mounting. Left/right stability control
is handled via brake-vectoring only.
AUTOMOTIVE ENGINEERING
LEXUS
Automotive Engineering - April 2023

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