CFD-guided optimization of the injector and injection parameters for light-duty GCI engine

•The complete ML-optimization of injector and injection parameters for GCI Engine.•Spray angle (SA) and start of injection (SOI) are the most important design parameters.•Two optimum SOI regimes at part-load and two preferable SAs at high-load were found.•10.7% reduction in fuel consumption at part-load and 7.5% at high-load were achieved.•The improvements by optimization were mainly caused by the increased air utilization.