Friction Reduction Trends in Modern Engines

A number of spark ignition engines from 1997 to 2003 are analyzed for their overall friction characteristics using the Willans line approach. This methodology appears to be quite robust across many different types of engines. Using a variety of partial and complete engine maps from multiple manufacturers, it is confirmed that engine friction has been decreasing over the decades (compared to past studies). Overall there has been a 25% reduction over 30 years. It is also demonstrated that thermal efficiency (defined here as the slope of fuel mep and bmep excluding enrichment) has been remaining steady during the same period. The application to aggregate engine models is discussed.