e-POWER is Nissan's hybrid system, a unique electrified powertrain that combines a compact gasoline engine and an electric motor. The gasoline engine is used solely to generate electricity which is distributed directly to the electric motor to drive the wheels, as well as to charge the battery if needed. The powertrain provides the smooth, effortless acceleration and refinement of an EV with the everyday convenience of traditional combustion vehicle ownership.

In addition to a new 5-in-1 design, which integrates core components of the electric powertrain into a more rigid, lighter unit for enhanced refinement, the third-generation e-POWER system adopts a breakthrough new 1.5-liter 3-cylinder turbocharged gasoline engine codenamed ZR15DDTe.

Thermal efficiency is a measure of how much energy from the fuel is converted into useful mechanical output (power) with the rest lost as heat. The greater the thermal efficiency an engine offers, the further it can drive on the same tank of gasoline. In the case of e-POWER, improving thermal efficiency leads to more efficient power generation.

Akihiro Shikata, Senior Manager of powertrain unit performance calibration development group, said "We began development by redefining the kind of engine required for a dedicated power generation unit. By relaxing the demands for engine responsiveness, we were able to design it to achieve optimal performance focused on the point of highest thermal efficiency and peak output."

The innovative new engine applied to Nissan's third-generation e-POWER, offers an impressive thermal efficiency of 42%.

To improve both thermal efficiency and engine output, the team adopted numerous additional technologies. They used a dedicated turbocharger larger than what is typically applied to a 1.5-liter engine, to reduce pump losses. Coupled with innovative valve timing adjustments and measures to avoid knocking, they were able to set an ideal ignition timing even with a high compression ratio. As a result, they achieved a high compression ratio of 13:1, which is rare for a turbocharged engine, successfully balancing high thermal efficiency with high power output.

Throughout the development, the team faced significant challenges not only in achieving high thermal efficiency but also in maintaining high output. Under conditions of high compression ratio and high boost pressure, abnormal combustion (pre-ignition), where the fuel ignites before the spark, tends to occur more easily, potentially damaging the engine. However, through meticulous control technology, they succeeded in preventing this.

Additionally, large turbochargers typically feature ‘lag' which causes a delay in engine torque response, however by leveraging the energy management features of e-POWER, the team ensured that vehicle acceleration was unaffected, overcoming this issue as well.

A key element of developing the new engine was delivering smooth airflow from the intake port into the combustion chamber, resulting in a strong tumble flow. In conventional engines, the design of the intake port is constrained by the necessity for press-fitted, sintered valve seats, which limit the ability to optimize port shape for ideal tumble flow.

Nissan engineers explored numerous options in long term technology development to address this challenge and determined that ‘cold spray technology,' which has been used in the aerospace, energy, heavy equipment, oil and gas, and other manufacturing industries, provided an advantage in terms of reliability and quality.

The process incorporates a specially developed alloy, in-house nozzles inspired by polishing techniques built up in forging mold production, resulting in a world-first application within an automotive engine.

Naohiro Yoshida, Chief Powertrain Engineer said, "From the beginning, we knew it would be difficult; however the team enjoys a challenge and knew customers would appreciate the benefits of our e-POWER technology even more when we succeeded. In the end, we overcame it with the cooperation of our three Monozukuri divisions (R&D, Production, Purchasing), relevant departments and our partner companies."

By overcoming numerous complex technical challenges, the ZR15DDTe engine has achieved high performance as a dedicated power generation engine.

This new engine represents a major leap forward in the team's journey to create the ultimate e-POWER dedicated engine. Engineers at Nissan's R&D center in Atsugi, Japan, continue to work toward an ambitious long-term goal of achieving higher thermal efficiency in e-POWER dedicated engines, as well as applying technologies such as STARC across a wide range of Nissan engines.

It's all part of Nissan's ongoing effort to improve fuel economy, extend range, and reduce emissions. These initiatives support our goal of creating more sustainable mobility and delivering ever-higher satisfaction for customers around the world.