Overview of the New Surface Finishings for SI Bores

This paper presents some definitions about the bore surface finishing and its influence on the piston rings performance.

The surface finishing of a cylinder is in most of cases obtained by a machining process called honing. In recent years, developments and innovations to the honing process have been implemented. These new surface finishings are being implemented in order to improve the working condition of the system. Some of these developments are presented.

This paper also presents some benchmarking of bore finishing for SI engines and case studies showing the influence of the surface finishing on the rings performance, regarding wear, friction and lube oil consumption. The results showed that smoother bore surfaces presented lower friction coefficient and also lower wear on the rings and bores.

Finally a recommendation for bore finishing and its evaluation for modern SI engines is given.