Abstract In order to adapt to energy security and the changes of global-scale environment, further improvement of fuel economy and adaptation to each country’s severer exhaust gas emission regulation are required in an automotive engine. To achieve higher power performance with lower fuel consumption, the engine’s basic internal design such as an engine block and cylinder head were changed and the combustion speed was dramatically increased. Consequently, stroke-bore ratio and valve layout were optimized. Also, both flow coefficient and intake tumble ratio port were improved by adopting a laser cladded valve seat. In addition, several new technologies were adopted. The Atkinson cycle using a new Electrical VVT (Variable Valve Timing) and new combustion technology adopting new multi-hole type Direct fuel Injector (DI) improved engine power and fuel economy and reduced exhaust emissions. Variable cooling system with an electric water pump and Flow Shut Valve (FSV) improved fuel economy by reducing warm-up time and mechanical losses. Also, a newly developed variable oil pump has significantly reduced friction losses. By implementing these new technologies, the new naturally aspirated 2.5L gasoline engine achieved over 40% thermal efficiency and over 150kW engine power. In combination with a new 8 speed Automatic Transmission, fuel consumption was reduced by over 16%. Introduction For future energy and environmental issues, it becomes more and more important to realize a sustainable society. CO2 must be reduced and additional fuel economy improvement is needed for all engines.In addition, future engines need clean exhaust gas emissions to meet not only the more severe regulation of various countries, but also European PN (Number of Particulate) regulations. On the other hand, it is a universal fact that the importance of high performance and superior drivability is needed to realize “fun-to- drive” that exceeds the customers’ expectation. To meet this challenge, incremental improvements to the engine are not enough. So, it is necessary to redesign of the basics such as stroke-bore ratio and valve layout. The new engine based on new TNGA (Toyota New Global Architecture) architecture was developed [1,2,3]. In recent years, we made efforts in Thermal Efficiency improvement and achieved 40% of Thermal Efficiency of the world TOP in the engine for the hybrid vehicle. However, in order to achieve the higher target of Thermal Efficiency, we paid our attention to a particularly high-speed combustion technology for various loss reduction. We must achieve not only the improvement of fuel economy but also the performance at a higher level. Figure 1 shows the trend and new engine’s target of the specific power and thermal efficiency. The performance target of maximum thermal efficiency of HEV (hybrid vehicle) was set at 41%. Even though this is a conventional engine, the target was set at 40%. This is the same as the one achieved by 2ZR-FXE (New Prius [ 4]), and the target of the specific power is set at 60kW/L and higher in order to bring customers more joy from driving.The New Toyota Inline 4-Cylinder 2.5L Gasoline Engine 2017-01-1021 Published 03/28/2017 Masashi hakariya Toyota Motor Co., Ltd. Tadashi Toda and Mitsuto Sakai Toyota Motor Corp. CITATION: hakariya, M., Toda, T., and Sakai, M., "The New Toyota Inline 4-Cylinder 2.5L Gasoline Engine," SAE Technical Paper 2017-01-1021, 2017, doi:10.4271/2017-01-1021. Copyright © 2017 SAE InternationalFigure 1. Trend and new engine’s Target of Specific Power and Thermal Efficiency This new naturally aspirated inline 4 cylinder 2.5L gasoline engine is the first mass produced TNGA engine to realize these targets. Engine Overview In order to achieve 40% of Maximum Thermal Efficiency and 60kW/L of Specific Power, High-Speed combustion package that can achieve high tumble ratio and flow coefficient has been developed. Furthermore, we implemented new devices such as Mot