[Tech Report] "The Hybrid Era Has Returned"... Toyota vs Hyundai Motor Technology Competition

Toyota Secures Technology Lead with World's First Mass-Produced HEV
Latecomer Hyundai Narrows Gap, Reaches Technology Peak
Series-Parallel vs Parallel... Difference Lies in Clutch Usage
Toyota Excels in Urban Driving, Hyundai Dominates High-Speed Driving

As global demand for electric vehicles declines, the time for hybrids (HEVs) has arrived. Toyota, which produced the world's first mass-produced HEV, the Prius, in 1997, has been a dominant presence in the HEV market from past to present. Competitors, including Hyundai Motor Company, spent years developing new technologies to avoid Toyota's patents on the 'complete hybrid.' However, Hyundai's HEV technology, which has now begun to follow its own path, has also reached its peak. This means that Toyota and Hyundai are ready to compete seriously in the global market with HEVs.

Earlier this month, Toyota Motor Korea opened the 'Toyota Training Academy' in Yongin, Gyeonggi Province. This move is aimed at increasing investment and expanding market share in the Korean market, where the HEV trend is gaining momentum. Toyota is implementing a 'multi-pathway' strategy that offers vehicle models tailored to the energy supply and demand situation of each region.

Hyundai Motor Group is also increasing the proportion of HEVs in its electrification strategy. It plans to operate HEV lineups for most major models to fill the gap caused by the slowdown in electric vehicle (EV) demand. Hyundai Motor Group intends to adjust the proportions of internal combustion engines, HEVs, and EVs through its characteristic flexible production strategy.

Hyundai Sonata Hybrid (left in the photo) and Toyota Camry Hybrid [Photo by each company's homepage]

Toyota Series-Parallel vs. Hyundai Parallel... The Difference Lies in Clutch Usage

Comparing the HEV systems of the two companies, Toyota adopts a series-parallel HEV system, while Hyundai uses a parallel HEV system. Both run on electric motors at low speeds and engage the engine at high speeds, allowing the vehicle to run using both engine and motor power.

The biggest difference is the number of motors and the presence of a clutch and transmission. Toyota's series-parallel HEV has two motors. One motor drives the vehicle while the other charges the battery. However, since there is no clutch, the motor and engine are always connected and run together. Because of this, during acceleration, the engine RPM is raised to the level that produces maximum efficiency, and the surplus power is used to charge the battery. This method results in high fuel efficiency.

On the other hand, Hyundai's parallel system has one motor. There is a clutch between the engine and motor that engages or disengages them depending on speed. At low speeds, the clutch is open, allowing the vehicle to run on the motor alone, while at high speeds, the clutch engages to use both engine and motor power simultaneously. However, it cannot charge the battery while driving.

So, what about real-world fuel efficiency? Theoretically, Toyota's series-parallel system offers higher fuel efficiency because it can store (charge) the engine's surplus power in the battery while driving. However, when comparing the combined fuel efficiency of mid-size sedans equipped with the same 18-inch tires, the Hyundai Sonata Hybrid and Toyota Camry Hybrid both achieve 17.1 km per liter.

HEV fuel efficiency is determined by various factors such as weight, battery capacity and efficiency, design, and aerodynamic drag coefficient. Hyundai compensated for the inability to charge while driving by simplifying the structure and reducing weight. The curb weight of the Sonata HEV is about 50 kg lighter than the Camry HEV.

Toyota Excels in Urban Driving, Hyundai in High-Speed Driving

When comparing actual driving experiences, Toyota has an advantage in urban driving, while Hyundai excels in high-speed driving. In the previously mentioned real-world fuel efficiency comparison between the Camry and Sonata HEVs, the Camry leads in urban driving with 17.3 km per liter compared to the Sonata's 16.8 km per liter. Conversely, at high speeds, the Sonata achieves 17.4 km per liter, outperforming the Camry's 16.8 km per liter.

Toyota's HEV system is optimized for urban driving because it uses a relatively large motor. The section where maximum instantaneous acceleration (torque) can be produced by the electric motor alone is extended. This minimizes engine intervention during urban driving, resulting in almost no perceptible discomfort when switching between engine and motor driving.

In contrast, Hyundai's HEV system is strong in high-speed driving. Although it uses a smaller motor with lower torque, it has a transmission that can continuously increase the motor's gear ratio. This means that even with a small motor, it can continuously create a range where maximum torque is available. This helps to continuously supplement motor power during high-speed driving, thereby improving fuel efficiency.