In the automotive industry, embedded systems and software play an increasingly important role in defining the characteristics of the vehicles. Both the vehicles and the embedded systems are designed as product lines, and two distinct rchitecture processes can be identified. The revolutionary process develops the architecture of a new product line, and focuses on abstract quality attributes and flexibility. The evolutionary process continuously modifies the architecture due to changes, such as additions of new functionality. In this paper, the evolutionary process is investigated through a case study. The study reviews a number of changes to an existing architecture, observing the cause of the change, what quality attributes were considered, and what technical aspects were included. It is also analyzed how the interplay between the two processes can be improved through systematic feedback about what evolution actually takes place.