Heat oven to 325°F. Generously spray 12-cup fluted tube cake pan with baking spray with flour.
In large bowl, beat cake mix, water, oil, sour cream, ground ginger and eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Stir in crystallized ginger. Pour batter into pan.
Bake 43 to 48 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes. Place cooling rack or heatproof serving plate upside down on pan; turn rack and pan over. Remove pan. Cool completely, about 1 hour.
In small bowl, stir frosting ingredients until well blended. Spoon over cake. Store loosely covered.