The RB26DETT is a inline six nissan engine that was based on the RB20 used in standard R32 Skylines in is taken to 2.6 litre from 2.0 litre and given twin turbos, the engine is used in R32, R33, R34 GTR Skylines.
"RB" refers to engine model,
"26" refers to capacity,
"D" refers to Double overhead cams
"E" is electronic fuel injected
"TT" is Twin Turbo
same applys to other nissan engines
the new G35 Skyline will use a new VQ35DETT Twin turbo V6 engine, Basicly the same as the 350Z engine
by the way it is a inline 6 with 4 valves per cylinder so it has 24 valves (24V)
as seen in Gran Turismo these engines can produce large amounts of power 1000hp+