Development of the Combustion System for the General Motors Fifth Generation “Small Block” Engine Family

The fifth generation of General Motor's “Small Block” 90-degree V engine family has been developed with a totally new combustion system. This system employs direct fuel injection (DI) and carefully architected in-cylinder flow field development in order to significantly improve all aspects of combustion system performance. Efficiency improvements stem from increased compression ratio, greatly improved dilution tolerance, and excellent knock resistance. The asymmetric, 2-valve (2V) layout of the “Small Block” engine presented unique challenges in developing the combustion system, but also offered unusual opportunities for an elegant solution while retaining the traditional “Small Block” attributes of packaging efficiency and power density. GM's comprehensive combustion system design and development process utilizing parametric design tools, airflow testing, engine and vehicle simulation, computational fluid dynamics modeling, and single-cylinder and multi-cylinder engine testing allowed for thorough optimization. This paper will highlight the design and development process and its application to four of the design alternatives considered in arriving at the final architecture.