1. Beat sugar and oil at medium speed with an electric mixer until blended. Add eggs, 1 at a time, beating after each addition.
2. Combine flour, 2 teaspoons baking soda, and next 4 ingredients. Gradually add flour mixture to sugar mixture, beating at low speed just until blended. (Batter will be stiff.)
3. Whisk together mashed sweet potatoes, 2/3 cup water, and 1 teaspoon vanilla extract. Stir into batter until blended. Fold in chopped toasted pecans. Pour batter into a greased and floured 10-inch tube pan.
4. Bake at 350° for 1 hour and 15 minutes or until a long wooden pick inserted in center comes out clean. Cool completely in pan on a wire rack.
*1 (16-ounce) can candied yams, mashed, or 1 (15-ounce) can pumpkin may be substituted for mashed sweet potatoes.