Nissan has achieved a 42% thermal efficiency in its latest e-Power combustion engine, a significant improvement over conventional engines that typically operate in the 30-40% range. This breakthrough demonstrates that internal combustion engines still have room for development, even as the automotive industry shifts towards electric vehicles. The core innovation lies in how the engine is used: not to directly power the wheels, but to generate electricity for an electric motor.
The e-Power System: A Series Hybrid Approach
Nissan’s e-Power system, first introduced in 2016 and now in its third generation, is a series hybrid. This means the 1.5-liter petrol engine acts solely as a generator, charging a battery that then powers the electric motor driving the wheels. This setup allows the engine to operate at its most efficient speed without the fluctuating demands of a conventional drivetrain.
The Qashqai is the first vehicle to utilize this latest iteration of e-Power, with production beginning in the UK last year. The system can even bypass the battery at high speeds, feeding power directly to the motor while simultaneously recharging.
Why Efficiency Matters: The Combustion Engine’s Weakness
Traditional combustion engines waste a substantial amount of energy as heat. Only a fraction of the fuel’s energy is converted into useful mechanical power. While modern engines have improved, reaching over 30% efficiency, the fundamental limitation remains. Nissan’s approach circumvents this by optimizing the engine for a single purpose: generating electricity, rather than directly driving the vehicle.
This shift unlocks a different kind of optimization, where the engine can stay within its ideal operating parameters more often.
The STARC Combustion Strategy and Cold Spray Technology
Nissan’s 42% efficiency is achieved through a combination of technologies. The STARC (Strong Tumble and Appropriately Robust ignition Channel concept) combustion strategy focuses on maximizing fuel-air mixture burn efficiency. This involves creating a strong tumble effect as air enters the cylinders and refining ignition timing for optimal combustion.
A critical component is cold spray technology, which eliminates traditional valve seat inserts in the cylinder head. These inserts compromise airflow, but the new method sprays hardened material directly onto the cylinder head, allowing for more aerodynamic valve openings.
Turbocharging and Compression Ratio: Balancing Power and Efficiency
Nissan also implemented an unusually large turbocharger to minimize pumping losses and utilizes a high compression ratio of 13:1. These adjustments balance thermal efficiency with high power output, ensuring that the engine delivers both performance and economy.
The result is a powertrain that effectively leverages the combustion engine’s strengths while mitigating its weaknesses.
The e-Power system represents a pragmatic step forward in engine development, proving that even established technologies can be reimagined for improved efficiency and performance.
This innovation suggests that combustion engines may remain viable for longer than anticipated, especially as hybrid technologies continue to evolve.
