Closed loop engineering methods are presented which demonstrate the design of an instrument panel retainer for optimal system performance characteristics such as NVH (noise, vibration, and harshness) and component integrity during crash. These methods incorporate finite element analysis techniques in concert with data acquisition of component and systems test to provide a closed loop analysis to test correlation of performance. Upon validation of the instrument panel systems model for a specific performance attribute, options to improve the system performance or reduce the cost may be reviewed analytically, replacing the historical “cut and test” method.Furthermore, the manufacturing process definition for the retainer is developed concurrent with the plastic part design. Manufacturing analysis methods are used to determine material flow, part cooling, part shrinkage, and ultimately, retainer fit and finish profile. Potential engineering design modifications are reviewed analytically to determine impacts relative to the injection molding process definition; refinements to process are then determined for optimal plastic part integrity and dimensional quality.