Charge Motion Benefits of Valve Deactivation to Reduce Fuel Consumption and Emissions in a GDi, VVA Engine 2011-01-1221
Requirements for reduced fuel consumption with simultaneous reductions in regulated emissions require more efficient operation of Spark Ignited (SI) engines. An advanced valvetrain coupled with Gasoline Direct injection (GDi) provide an opportunity to simultaneously reduce fuel consumption and emissions. Work on a flex fuel GDi engine has identified significant potential to reduce throttling by using Early Intake Valve Closing (EIVC) and Late Intake Valve Closing (LIVC) strategies to control knock and load. High loads were problematic when operating on gasoline for particulate emissions, and low loads were not able to fully minimize throttling due to poor charge motion for the EIVC strategy. The use of valve deactivation was successful at reducing high load particulate emissions without a significant airflow penalty below 3000 RPM. Valve deactivation did increase the knocking tendency for knock limited fuels, due to increased heat transfer that increased charge temperature. Valve deactivation also extended the near un-throttled operation to lower loads (2 bar BMEP) by reducing burn durations and allowing higher levels of dilution. Results are presented showing the improvements in emissions and reduction in fuel consumption. Results from an optical engine and Computational Fluid Dynamics (CFD) at representative points are also presented to quantify the in-cylinder sprays and flow structures.