Geely-Renault B20 Hybrid Engine Works Underwater: IPX8

Waterproof hybrid powertrain aimed at serious off-road use

Horse Powertrain, the joint venture created by Renault and Geely in 2024, has unveiled a 2.0-liter four-cylinder engine engineered to keep running even when fully submerged. Codenamed B20, the unit carries an IPX8 waterproof rating and can operate after immersion up to 1.1 meters (about 3.6 feet). That capability positions it as a rare internal-combustion solution designed specifically for hybrid off-roaders that routinely face river fords and wet conditions.

Why this matters for hybrid and plug-in vehicles

Electric motors and battery systems are known to be sensitive to extreme water exposure, and conventional combustion engines are not typically built to be fully watertight. By contrast, the B20 addresses both mechanical and electronic vulnerabilities: its sensors and control modules are fully sealed, and Horse Powertrain says it uses special sealing between the engine and gearbox. When the system detects immersion, the engine management software automatically adjusts throttle response and limits output so the motor doesn't stall, allowing the vehicle to continue moving through deep water.

Key specifications and performance

The B20 is aimed at a range of hybrid architectures—conventional hybrids, plug-in hybrids and range-extended systems. Core numbers include:

• Displacement: 2.0 liters, inline four
• Power: 190–250 hp (depending on calibration)
• Torque: 300–380 Nm
• Assembled unit weight: around 130 kg
• Waterproof rating: IPX8 (operational after 1.1 m submersion)

Horse also claims the engine can handle extreme inclines, supporting 100% grades (about a 45-degree angle) when packaged in off-road-ready vehicles.

Efficiency: Miller-cycle and high thermal output

Beyond its waterproofing, the B20 emphasizes fuel economy. The engine runs on the Miller cycle, pairs direct fuel injection with bespoke pistons and high-swirl intake ports, and achieves a remarkable thermal efficiency of 48.4 percent. For context, most conventional gasoline engines average 25–30 percent efficiency, while the Miller-cycle unit in the Toyota Prius reaches roughly 40 percent. A dual active cooling system helps keep temperatures in check during long climbs or heavy loads.

Real-world rollout and market implications

This is not a concept prototype: the B20 debuted at the Beijing Auto Show and is already in production use on the Geely Galaxy Cruiser 700 SUV in China. There it operates as part of a plug-in hybrid system paired with Horse Powertrain's three-speed hybrid transmission. For manufacturers targeting rugged hybrids and adventure SUVs, a waterproof combustion engine could be a meaningful differentiator—offering confidence for buyers who expect both fuel efficiency and real-world off-road capability.

Highlights:

• IPX8 waterproofing enables 1.1 m fording
• Competitive power and torque for midsize SUVs
• Industry-leading thermal efficiency through Miller-cycle tech

Horse Powertrain's B20 may signal a new niche: hybrid powertrains that combine high efficiency with true water-fording robustness, appealing to customers who want electric-assisted efficiency without sacrificing off-road confidence.