2022 Grand Cherokee Plugs In
Jeep engineers combine the proven 4xe PHEV powertrain with the fifth-generation SUV.
Plug-in hybrids are a controversial subject in engineering and product-planning circles. With a modicum of electric-only capability and superior driving range but retaining the tailpipe emissions and cost/complexity burden of two powertrains, PHEVs are a polarizing yet ideal product for certain applications. Clawing confidently across Texas slickrock, with only its batteries providing drive torque to all four wheels, the all-new 2022 Jeep Grand Cherokee 4xe makes a strong case for PHEV in the SUV segment.
Off road operation is as quiet as a mountain bike to other trail users, and in moderate thermal conditions the “4-by-e” Grand Cherokee can travel up to 25 miles (40 km) before the long-stroke 2.0-L turbocharged Otto-cycle engine (part of Stellantis’ GMET family, made in Italy) engages. When it does, as SAE Media experienced during the 4xe’s recent launch event, the transition is smooth and nearly seamless. And in very cold ambient temperatures, the hybrid system defaults to combustion-engine power, based on coolant temperature, a feature that customers in four-season markets will appreciate. With 470 lb-ft (637 Nm) of total system torque on tap, there is a lot to like about the fifth-generation Grand Cherokee configured for plug-in duty.
Jeep planners and many customers agree. The Wrangler 4xe, with essentially the same hybrid-electric system as the Grand Cherokee, is the top-selling PHEV in North America. Jeep brand CEO Christian Meunier says “4-by-e is the new 4-by-4,” whether serving as a pathway to battery-electric Jeeps in 2025 or filling a longer role in the Jeep portfolio. The plug-in powertrain is available on the standard Grand Cherokee as well as Trailhawk, Overland, and Summit trims.
Simulation sped development
“We knew electrification was a requirement” for the 2022 model, explained Grand Cherokee vehicle line executive Tom Seel, “but it was also a requirement to not compromise the customer package or comfort.” The development team packaged the twin lithium-ion NMC battery packs as low as possible in the unibody structure, ahead of the second-row seat crossmember, to maintain a center of gravity conducive to good vehicle dynamics.
Each of the batteries, supplied by Stellantis partner Samsung SDI, contain 48 nickel manganese cobalt (NMC) cells, same as the Jeep Wrangler 4xe. The 400-volt system incorporates a dedicated thermal management system with coolant heater. It delivers a total of 17 kWh without intruding on the non-hybrid model’s rear occupant leg room (38.2 in./971 mm) and knee room (4.1 in./103 mm).
Seel described engineering the vehicle’s high-voltage cable routing as a balancing act between product and process. “All the routings had to be engineered for the [in-plant assembly] process,” he explained. “We completed, with manufacturing engineering, numerous virtual simulations of the process of connecting all the high-voltage cables prior to any hardware being built. This ensured that we’d have quality connections to support the electrified vehicle.”
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 (off-road) 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 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 all-electric 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, versus 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.