For Valeo Engine Cooling, CFD now plays a key role as a design tool in the optimization of its fans as shown in  . The next challenge has been to address installation effects found in the engine block compartment on the fan performances. A first step towards this goal has been to consider the interaction of the fan with the struts or the stators of its support.The potential gains of a stage configuration are first addressed by a dimensional analysis and a simplified radial equilibrium approach. The first CFD results achieved during the optimization of the rotor-stator system implemented on the new fan range are then presented. These are two-dimensional and three-dimensional Navier-Stokes predictions of steady state rotor-stator interaction with or without pitch change. Parametric studies on the stator stagger angle and shape have been performed. Results clearly evidence that inadapted stator geometry can lead to dramatic decrease of efficiency compared to the one obtained obtained without stators. Conversely, suitable stator profile can lead to noticeable pressure increase and flow re-alignment.