Development of a New 2L Gasoline VC-Turbo Engine with the World’s First Variable Compression Ratio Technology 2018-01-0371

A new 2L gasoline turbo engine, named KR20DDET was developed with the world’s first mass-producible variable compression turbo (VC-Turbo) technology using a multi-link variable compression ratio (VCR) mechanism. It is well known that increasing the compression ratio improves gasoline engine thermal efficiency. However, there has always been a compromise for engine designers because of the trade-off between increasing the compression ratio and knocking. At Nissan we have been working on VCR technology for more than 20 years and have now successfully applied this technology to a mass production engine. This technology uses a multi-link mechanism to change the top and bottom dead center positions, thereby allowing the compression ratio to be continuously changed.The VC-Turbo engine with this technology can vary the compression ratio from 14:1 for obtaining high thermal efficiency to 8:1 for delivering high torque by taking advantage of the strong synergy with turbocharging. This enables the engine to provide various characteristics intelligently and autonomously based on the driver’s demand.This paper presents an overview of the VC-Turbo engine and describes in detail the working principle, purpose and characteristics of the VCR mechanism. It also explains key performance technologies, including a newly developed combustion design, fuel supply system and turbocharger, which generate synergies with VCR for acceleration performance, fuel efficiency and NVH.