The D in the engine code stands for dual overhead camshaft (DOHC). This is attained by fitting an RB25DE or RB26DETT cylinder head and or turbo to an ordinary RB30E/T block. The RB25DET just isn't typically used.is a strong engine, powering about 3 generations on the Skyline GT-R. The legendary RB26DETT is revered around the world for its special c