Automotive Engineering - May 2022 - 12

ROAD READY
The 2022 Grand Cherokee 4xe's
all-electric drive mode has no
compromises in extreme off-road driving.
Maximum battery charge rate with an SAE J1772 connector
is 7.2 kW. According to vehicle synthesis manager Eunjoo
Hopkins, charging the 4xe on Level 1 requires 12-14 hours;
Level 2 charging takes 3-4 hours.
A naked Grand Cherokee 4xe chassis on display at the media
launch event showed a very robust, almost military-grade-looking
high-voltage electrical network. All connectors are sealed-
a requirement for Jeep's 24 in./609 mm water fording specification.
Across the underbody, 3.5-mm (.137-in.) steel skidplates
shield the batteries and electronic components.
With the battery packs positioned, Seel's team turned to
reengineering the exhaust system, incorporating an active
noise cancellation package with center sound resonator and a
transverse muffler in the rear. Positioning the inverter and
other key PHEV electronic modules, including a new electronic
brake module (it allows for increased rate of hydraulic pressure
build to facilitate torque transfer) required unique structures
to be added, Seel noted. The changes include a floorpan
stamping that is unique to the 4xe model. The plug-in, rated
at 57 mpg-e, uses a 19-gal. (72-L) fuel tank, versus the 23-gal.
(87-L) vessel used by the 3.6-L V6 and 5.7-L V8 models.
Close inspection of the 4xe chassis reveals how smart component
design helped solve various packaging challenges. The
densely-packed space around and under the ICE and ZF-licensed
8P75PH hybrid transmission include active engine mounts, an
electric power steering system (EPAS), an electrically-disconnecting
front sway bar, and a front drive module directly mounted
to the engine with half shafts that extend through the oil pan.
The sway bar system helps deliver a 455 ramp-travel index (a key
axle-articulation metric) that is a 20% improvement over the
previous-gen vehicle. Engineers also increased the OR2 (offroad)
suspension travel by 15 mm (.59 in.), enabling a total
ground clearance of 10.9 in. (254 mm) at full extension.
Useful drive modes
As on the Wrangler 4xe, the " e-Torque " hybrid system combines
a 44-hp (33-kW) engine-mounted (P1) belt-starter generator
delivering torque to the crankshaft and start-stop functionality,
with a 134 hp (100 kW) AC traction motor mounted
12 May 2022
P1-hybridized engine, EPAS, electronic sway bar and front axle
disconnects, active engine mounts and direct-to-engine axle mounting
make the Jeep WL's front end a tight space.
in the P2 position between the engine and 8-speed transmission,
replacing the torque converter. A clutch manages the
torque input from the 2.0-L engine; when the clutch is open,
the motor-generator drives the transmission for full-electric
operation. The system also manages the re-gen braking.
The 4xe uses a unique MP3028C active transfer case supplied
by Magna Powertrain, featuring a 2-High selection for improved
fuel economy. On Trailhawk models the T-case works with a ZF
rear electronic limited-slip differential to improve traction by vectoring
torque to the wheel with the most grip. When not in allelectric
mode, the 4xe operates as a hybrid, providing greater
range extension. The 4xe has a 3.70:1 rear-axle ratio, versus 3.45:1
for V6 and V8 models. The Trailhawk model's crawl ratio is 47.4:1,
compared with 44:1 for the ICE-powered Trailhawk.
Three drive mode buttons on the IP allow driver selection of
different driving modes. 'Hybrid' is the default. There's also
Electric Only and E-Save, which charges the battery and conserves
it for later use. In the E-Save mode, the driver can
choose between two sub-options: Battery Save, where the
vehicle uses all the available torque capacity while driving to
maintain battery charge at a pre-set limit; or Battery Charge,
which enables the 2.0-L engine to actively recharge the battery
while driving.The 4xe can also optimize regenerative energy
capture, via a driver-selectable Regen mode. The Max
Regen function allows for maximum regen capture.
Both the PHEV and conventional Grand Cherokees are built on
the same body line at Stellantis' Detroit Assembly-Mack complex.
Lindsay Brooke
AUTOMOTIVE ENGINEERING
FROM LEFT: MARK RICHARDSON; LINDSAY BROOKE
Automotive Engineering - May 2022

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