The World’s First Production Variable Compression Ratio Engine – The New Nissan VC-T (Variable Compression-Turbo) Engine

Authors

S. Kiga MEng, K. Moteki MEng, S. Kojima BEng, Nissan Motor Co., Ltd., Kanagawa, Japan

Year

2017

Print Info

Fortschritt-Berichte VDI, Series 12, No 802

Summary

Improving gasoline engine thermal efficiency is a key development target which can be enabled by increasing the compression ratio. However, there has always been a compromise for engine designers because of the trade off between increasing the compression ratio and knocking. A solution has long been the actual realization of variable compression ratio technology. Nissan has been working on variable compression ratio technology for more than 20 years and has 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-T (Variable Compression-Turbo) engine with this technology can vary the compression ratio from 14 (thermal efficiency) to 8 (high power), thereby achieving a better-than-ever balance between fuel efficiency and output performance. This paper describes the working principle, purpose and characteristics of the Nissan developed multi-link variable compression ratio mechanism, key points of design optimaization for mass production and the benefits that can be obtained from it.