Jeep Took Toyota’s Hybrid Idea and Added a Turbo. Here’s How It Can Still Do Jeep Stuff.
What it took to make the “Hybrid Synergy Drive” idea Toyota patented tow and climb like a Jeep.
Frank MarkusWriterManufacturerPhotographerSep 10, 2025
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That goofy-looking original Toyota Prius introduced the world to a funky new type of hybrid system that used a single planetary gearset that the 2026 Jeep Cherokee is about to replicate. In these systems, a small motor-generator turns a central “sun” gear with teeth on the outside, a much more powerful electric motor turns a ring gear lined with inward-facing gear teeth (this one is also connected to the wheels), and the gas engine engages the carrier holding a set of little “planet” gears that mesh with the sun and ring gears.
It’s a pretty neat and super-smooth setup that allows both motors and the engine to contribute when accelerating hard from low to moderate speeds. In all other conditions, that smaller motor-generator serves to regulate the speed of the engine and wheel speed, recapturing energy as it does so. It also acts as the starter and alternator.
Ford licensed the Toyota patents and engineered its own hybrids using the same idea. Mazda and Subaru hybrids work the same way. But all such existing “planetary combiner” hybrids have one major difference relative to this new Jeep application: Their engines have all been naturally aspirated, and most employ an ultra-efficient Atkinson-cycle cam phasing scheme, in which the intake valves close late. (That makes the power stroke, which turns the wheels, “feel” longer than the compression stroke that burdens the engine.) Jeep is stirring things up as the only player to use a turbocharged engine with its planetary combiner. We asked Micky Bly, head of global propulsions systems about this decision.
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How Does Turbocharging Affect Economy and Performance?
Turbocharging allows a smaller, more efficient engine to deliver peak performance and towing capability, while the two-motor planetary system keeps the combustion engine working in its efficiency sweet spot for more of the time. This combination helps deliver the higher specific torque needed for towing up steeper grades with less of a displacement penalty, and the turbo maintains expected performance levels at higher altitudes.
How Did this “Prince” Engine Change for Hybridization?
While the basic engine architecture does stretch back to the original BMW/PSA (Peugeot/Citroën) “Prince” engine from 2006, it’s as unrecognizable as the proverbial hammer that’s had three new heads and four new handles. This third-gen engine, now dubbed EP6 and produced in Dundee, Michigan, is making its North American debut in the Cherokee. The following changes were made to tailor it for planetary hybrid duty:
Combustion phasing and valve timing widens the high-efficiency operational “island” on the engine’s load-vs-speed map, taking advantage of the electric assist
Cam phasing is broadened to allow Miller-cycle (think Atkinson, but with turbo- or supercharger boost) efficiency while maintaining performance and towing capability
Boost and exhaust-gas recirculation (EGR) strategies are modified to account for frequent engine starts and rapid load transitions
Thermal management (coolant routing, integrated exhaust manifold, catalyst light-off strategy) is optimized for hybrid duty cycles
The engine-mount tuning and the flywheel and inertial damping are optimized to make the frequent engine starts and stops feel seamless
Accessories are electrified as needed
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Why Not Use the European 1.6-Turbo Hybrid Setup?
Peugeot, Citroën, DS, Opel, and even Jeep (Compass 4xe) employ this engine in Europe in plug-in hybrid (PHEV) applications. That system places a 123-hp/87-lb-ft motor between the engine and a seven-speed twin-clutch automatic transmission. But it was designed for different customers, duty cycles, package envelopes, and manufacturing footprints. For Cherokee, the planetary power-split architecture was deemed the best fit to meet North American performance, towing, efficiency, and off-road drivability targets in this segment without adding the mass and cost of a PHEV battery pack.
How Does the Cherokee System Compare With:
Toyota Hybrid Synergy Drive: It’s conceptually similar in using a planetary gearset to split/merge power, but differs materially in terms of overall control strategy, motor sizing, mechanical ratios, and how torque is delivered for off-roading and towing.
Ford Escape/Maverick Hybrid: Here, battery and motor sizing are quite different, mechanical gear ratios, thermal strategy, and all-wheel-drive integration differ, with Jeep getting better crawl/creep tuning.
Mazda CX-50/Subaru Forester Hybrids: These versions’ naturally aspirated engines and specific motor/ratio choices are optimized for urban efficiency. Cherokee’s boosted engine calibration is optimized for gradeability, operation at altitude, and for low-speed torque modulation off-road.
We’re eager to compare the new Cherokee with America’s other 1.6-liter turbo hybrid options: The Hyundai Tucson and Kia Sportage hybrids. These compact SUVs put a single electric motor where the torque converter would otherwise go in a conventional six-speed automatic transmission. It pitching these models against one another, we’ll expose them all to the off-road, towing, and altitude conditions for which the Jeep was optimized—and then compare their efficiency.
Frank Markus
I started critiquing cars at age 5 by bumming rides home from church in other parishioners’ new cars. At 16 I started running parts for an Oldsmobile dealership and got hooked on the car biz. Engineering seemed the best way to make a living in it, so with two mechanical engineering degrees I joined Chrysler to work on the Neon, LH cars, and 2nd-gen minivans. Then a friend mentioned an opening for a technical editor at another car magazine, and I did the car-biz equivalent of running off to join the circus. I loved that job too until the phone rang again with what turned out to be an even better opportunity with Motor Trend. It’s nearly impossible to imagine an even better job, but I still answer the phone…
