## 1 Introduction
[15]; results show that variable inlet pre-whirl increases the stable operation of the compressor near surge, and an improvement in torque of 42% is estimated. Experimental and model-based assessments were conducted by [PERSON] et al. [16]; changing the pipe dimension upstream of the compressor, both showed differences in amplitude and frequency of pressure pulses when the compressor is operating near the deep surge limit. The same concept of bent pipes was assessed using CFD by [PERSON] et al. [17] to investigate an unsteady flow field and its effects on inflow pulsations. The idea of a lumped parameter model used for the prediction of the impact of piping systems on surge characteristics in centrifugal compressors was presented by [PERSON] et al. [18]. PIV and Large Eddy Simulation (LES) were performed on ported shroud compressor to assess flow separation in the inlet and outlet of the compressor housing, as described in [19]. Using an artificial neural network (ANN) and regression analysis, researchers in [20] predicted and analyzed the non-uniform distorted flow occurring at transonic compressor operating conditions using CFD. The CFD assessment results provided a robust modeling tool for predicting pressure distortion at the tip and hub branch in such operating conditions. Dual entry compressor concepts were also assessed, looking for an improvement in compressor performance and surge mitigation; such systems have shown compressor stability at different altitudes by increasing the strength at the inlet boundary, as mentioned in [21]. Variable geometry orifices (VGO) were assessed for improvements in compressor performance at low-end torque. Results show about 3% improved compressor efficiency at low mass flow rates. Furthermore, the VGO had to be deactivated at higher mass flow rates as VGO induced flow losses and degraded the compressor performance, as shown by [PERSON] et al. [22]. New generation turbocharged powertrains need to meet the future emission standards described by [PERSON] et al. [23] and lay a path for upcoming engines and range extenders, such as the two-stroke Direct Injection (DI) engine presented in [24]. Extensive research is also available on the performance of turbines proposed by [PERSON] et al. [25] and in extreme off-design conditions [26]. The existing literature is particularly limited to the analysis of compressor technologies using a modeling approach, such as CFD simulations. However, very little experimental information is included. In addition, the impact of the technology on a realistic application has not been evaluated. In this study, the innovation lies firstly in testing and evidencing the influence of the VGO technology on compressor maps from an experimental perspective. Following this line of investigation, the differences are evaluated in the context of a state-of-the-art automotive engine, using an experimental approach. Finally, part of the innovation and contribution to this field of this study is evidenced in the development of a 1D engine and turbocharger modelling, based on which further analysis can be performed regarding steady state and transient operation. In summary, this study contributes to understanding in which scenarios it would be interesting to use this technology and quantifies its impact. Two compressor prototypes in steady state and at heavy transient operation are assessed. Not only are the compressor improvements evaluated but also the side effects on engine operation. An analysis of engine behavior is first attempted from an experimental point of view. A modeling methodology is proposed to overcome the experimental uncertainties and variability. For this, a description of the method followed is included in Section 2. In Section 2.1, detailed information on the experimental setup in both steady state and transient engine operation is provided. In Section 2.2, the results of model development and validation results are presented. Results regarding steady states and transients modeling are shown in Sections 3.1 and 3.2.