%0 Journal Article %T Improving diesel engine efficiency at high speeds and loads through improved breathing via delayed intake valve closure timing %A Cody M Allen %A Gregory M Shaver %A James McCarthy %A Kalen R Vos %A Lisa Farrell %A Xueting Lu %J International Journal of Engine Research %@ 2041-3149 %D 2019 %R 10.1177/1468087417743157 %X Valve train flexibility enables optimization of the cylinder-manifold gas exchange process across an engine¡¯s torque/speed operating space. This study focuses on the diesel engine fuel economy improvements possible through delayed intake valve closure timing as a means to improve volumetric efficiency at elevated engine speeds via dynamic charging. It is experimentally and analytically demonstrated that intake valve modulation can be employed at high-speed (2200£¿r/min) and medium-to-high load conditions (12.7 and 7.6£¿bar brake mean effective pressure) to increase volumetric efficiency. The resulting increase in inducted charge enables higher exhaust gas recirculation fractions without penalizing the air-to-fuel ratio. Higher exhaust gas recirculation fractions allow efficiency improving injection advances without sacrificing NOx. Fuel savings of 1.2% and 1.9% are experimentally demonstrated at 2200£¿r/min for 12.7 and 7.6£¿bar brake mean effective pressure operating conditions via this combined strategy of delayed intake valve closure, higher exhaust gas recirculation fractions, and earlier injections %K Variable valve actuation %K intake valve modulation %K dynamic charging %K volumetric efficiency %K fuel economy %U https://journals.sagepub.com/doi/full/10.1177/1468087417743157