The Bz.IV was a dual-camshaft design, with two intake and two exhaust valves per cylinder. The cylinders were cast iron surrounded by a sheet metal cooling jacket. The crankcase was aluminium and pistons were initially steel but later versions had aluminium pistons. A high compression version of the engine (Bz IVü) was produced from 1917 onwards and can be recognised by the red bands painted on each cylinder. In February 1918, pistons from Bz.IV were the first captured aluminium pistons to be examined by the British Ministry of Munitions.