A New Kind of Hybrid: Aramco’s Radical Powertrain Reimagines Things With Cost-Effective Retro-Tech

Aramco? Isn’t that the Saudi Arabian Oil Company—aka “the world’s largest oil producer”? What is it doing designing a Dedicated Hybrid Engine (DHE) powertrain? Well, it’s heavily vested in keeping combustion engines relevant, and with hybrids attracting more buyers than battery-electric vehicles in some regions, a better hybrid “mousetrap” could be just the thing to keep folks queuing up at gas pumps indefinitely.

Also note this DHE isn’t Aramco’s only dog in the hybrid fight. Remember Horse Powertrain, the joint venture formed when Renault and Geely/Volvo spun off their combustion-engine operations? Those companies each hold 45 percent of the new JV, and Aramco owns the remaining 10 percent.

Horse specializes in turnkey engines or range-extenders that allow companies to quickly and easily hybridize a combustion platform or add a range-extender to an existing battery-electric model. Aramco’s DHE looks to answer the question, “If you were designing the ideal new hybrid powertrain from scratch, what would it look like?”

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Hybrid Synergy Drive for 2030?

An engine connecting to a motor-generator via planetary gears sounds very Toyota. First big difference: DHE features one such motor-generator-planetary setup at each end of the crankshaft. Second big difference: The engine itself is radically re-envisioned with laser focus on thermodynamic efficiency and cost reduction, leveraging a strong-hybrid duty cycle that seldom demands low-rpm torque or high-rpm power from the engine, but instead can run for extended periods occupying an “efficiency island” in the load/speed operation graph.

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The Engine

The initial proof-of-concept features a 1,599cc inline three-cylinder engine. To keep it notably compact, it’s a cam-in-block pushrod design. To keep it simple, it features a monoblock casting with no separate cylinder head and uses just two valves per cylinder with no variable timing or lift. To minimize friction, there are no journal bearings—the crank, camshaft, and connecting rods all ride on roller bearings, and the crank is offset 12 millimeters from the cylinder-bore centers to reduce piston side loading. There’s also no accessory drive; all auxiliaries including the water pump operate electrically on demand.

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Combustion Optimization

The chamber is undersquare (82-mm bore, 101-mm stroke) for reduced surface-to-volume ratio, which reduces heat loss to boost thermal efficiency. The more compact chamber reduces crevice volumes that can trap hydrocarbons, while a high-tumble/low-swirl intake design using direct and port injection promotes faster, more efficient and complete combustion. High mechanical compression combines with a late intake-valve closing (LIVC) strategy that reduces effective compression while preserving the full expansion ratio to extract maximum work from the combustion. Introducing cooled EGR reduces throttling losses under lighter load. Engine thermal efficiency is said to be in the 41–42 percent range. Further efficiency improvements are also envisioned, including pre-chamber ignition (using a Mahle-type passive chamber and spark-plug insert), increasing compression from 13:1 to 15:1, and reducing exhaust back-pressure by replacing the turbo with an e-booster. Hydrogen fueling is foreseen as yet another future decarbonizing option.

Designed in Detroit, Built in France

This project is being developed at Aramco Americas Detroit Research Center by Nayan Engineer. If his name rings a bell, he helmed a gasoline direct-injection compression-ignition (GDCI) program at Hyundai that we reported extensively on before that company—along with Mercedes-Benz (DiesOtto) and General Motors (HCCI)—all figured out you can’t have your diesel-engine fuel economy and eat gas-engine cost and emissions, and canceled those programs. His small team conceived of the engine, and French motorsports engine manufacturer Pipo Moteurs developed it and built two running prototypes that are now undergoing testing.

The Electric Bits

Each end of the crankshaft connects to the planet carrier of an epicyclic gearset. The sun gear on each side attaches to a motor functioning primarily as a generator, and the outer ring gear connects to a primary traction motor geared to the wheel. As with Toyota Hybrid Synergy Drive, the car can be driven with the engine on or off (making it suitable for HEV or PHEV/range-extender duty), and with two planetary arrangements, there’s no need for a differential (offsetting some of the cost of the two planetary and reduction-drive gear sets). Note that a common lubricant is shared with the engine and the planetary gear sets. An upgrade to axial-flux traction motors is also envisioned, which would further shrink the DHE powertrain’s overall width.

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A Modular Powertrain Family

The naturally aspirated 1.6-liter I-3 has been built for testing, but simulation of the engine in a Camry-size sedan revealed insufficient power to scale Loveland Pass. So a turbocharged unit was also developed. But the design is modular, and Engineer foresees a range of engines using the same combustion chamber, including a 1.1-liter parallel two-cylinder, a 2.1-liter V-4, and a 3.2-liter V-6 (V engines bolt two monoblocks together), with each available in naturally aspirated or turbocharged guises. And with a longitudinal mid-mounted powertrain driving front and rear differentials, the powertrain provides all-wheel drive, which might be a great opportunity to leverage the design’s dry-sump lubrication system and lean the engine over to fit under a floor.

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How Cheap?

Eliminating a cylinder head drastically reduces machining costs, and Engineer’s parts count for the naturally aspirated I-3 is just 175. His team is working to generate a comparative number for a Toyota Prius DOHC 16-valve I-4, but suffice to say it’s bigger. Yes, assembling a crankshaft with roller bearings is more expensive than simply clamping a cast crank into a bedplate, and the bearings themselves are pricier than journal bearings. Aramco’s DHE also calls for twice as many motor-generator-epicyclic gear-set combos, but if combined motor power matches that of a Prius, each motor can be smaller and use fewer rare-earth magnets and so on.

Calculations by Engineer’s team suggest a naturally aspirated I-3 DHE could deliver a 35 percent drop in fuel consumption at an upcharge of $3,800 relative to a conventional port-injected DOHC four-cylinder in a midsize sedan, and that a naturally aspirated V-6 DHE would deliver similar fuel savings relative to a port-injected DOHC V-6 in a midsize SUV for $4,080. Again, using Aramco’s math, that’s a few percentage points more fuel savings for roughly 20-plus percent less money than a strong power-split hybrid (like Toyota HSD) would cost.

So Are Any OEMs Interested?

There was a pretty full house at the 2026 Society of Automotive Engineers’ World Congress session covering DHE, but with U.S. patent number U.S. 12,558,950 B2 having only been granted on February 24 of this year, Aramco is only now beginning to shop the engine around. Stay tuned for further developments.