The Daimler D.IIIb was a V-8, water-cooled, piston engine developed in Germany by Daimler Motoren Gesellschaft, for use in aircraft in 1918.
Little is known of the Daimler D.IIIb, (not related to the Mercedes D.III), other than it was used for a succession of Daimler fighter prototypes in 1918.
Data from:The Complete Book of Fighters & German Aircraft of the First World War