Predictive GT-Power Simulation for VNT Matching to EIVC Strategy on a 1.6 L Turbocharged GDI Engine 2019-01-0192

The use of early intake valve closing (EIVC) can lead to improvements in spark-ignition engine efficiency. One of the greatest barriers facing adoption of EIVC for high power-density applications is the challenge of boosting as EIVC strategies reduce volumetric efficiency. Turbochargers with variable nozzle turbines (VNT) have recently been developed for gasoline applications operating at high exhaust gas temperatures. The use of a single VNT as a boost device may provide a lower-cost option compared to two-stage boosting systems or 48 V electronic boost devices for some EIVC applications. A predictive model was created based on engine testing results from a 1.6 L turbocharged gasoline direct injection engine [1]. The model was tuned so that it predicted burn-rates and end-gas knock over an engine operating map with varying speeds, loads, compression ratios and fuel types. Using the model, an assessment of VNT performance was implemented using compressor and turbine maps made available from Garrett Motion, Inc. Results show that the single VNT device supports mild EIVC across the operating map while maintaining acceptable full-load performance and maintaining or improving upon thermal efficiency compared to a twin-scroll turbocharger. This work was done as part of the Environmental Protection Agency’s regulatory assessment of advanced light-duty automotive technologies.