A numerical procedure for the calibration of a turbocharged spark-ignition variable valve actuation engine at part load

Referring to spark-ignition engines, the downsizing, coupled to turbocharging and variable valve actuation systems are very common solutions to reduce the fuel consumption at low-medium engine load. The adoption of such solutions increases the complexity of engine control and management because of the additional degrees of freedom. In this work, a twin-cylinder turbocharged variable valve actuation spark-ignition engine is numerically investigated by a one-dimensional model (GT-Power™). The considered engine is equipped with a fully flexible variable valve actuation system. In the first stage, one-dimensional engine model is validated against the experimental data at full and part load. The validated model is then integrated in a multipurpose commercial optimizer (modeFRONTIER™) with the aim to identify the engine calibration that minimizes fuel consumption at part load. The adopted optimization approach shows the capability to reproduce with good accuracy the experimentally identified calibration. The optimization underlines the advantages of an engine calibration based on a combination of early intake valve closure strategy and intake throttling rather than a purely throttle-based calibration. The developed automatic procedure allows for a ‘virtual’ calibration of the considered engine on completely theoretical basis and proves to be very helpful in reducing the experimental costs and the engine time-to-market.