The D within the engine code means twin overhead camshaft (DOHC). This is achieved by fitting an RB25DE or RB26DETT cylinder head and or turbo to a normal RB30E/T block. The RB25DET is not really generally used.is a sturdy engine, powering around a few generations in the Skyline GT-R. The legendary RB26DETT is revered across the globe for its one o