RB Engines - RB20DET, RB25DET, RB25DET NEO, RB26DETT

[Little Kez]

R32 Skyline
The bread-and butter performance model in the 1989 R32 Skyline range is the GTS-t.



The GTSt uses a silver rocker cover version of the RB20DET using an improved cylinder head, larger ceramic turbo, more sophisticated ECU and a blow-off valve. The static compression ratio remains at 8.5:1.

The R32-spec RB20DET comes hooked to either a 5-speed manual or 4-speed auto trans. An AWD version – the GTS4 – is also available and makes the same power and torque.

Of course, the most groundbreaking RB engine development appeared in the 1989 R32 Skyline GT-R – Godzilla!



The R32 GT-R’s RB26DETT engine is the big-banger of the twin-cam RB family – its 86mm bore and 73.7mm stroke achieve a swept capacity of 2.6 litres. The compression ratio remains at 8.5:1 and the twin-cam, 24-valve head features sodium-filled exhaust valves and bucket-type cam followers to allow engine speeds up to the 8200 rpm limiter.

Separate cast iron exhaust manifolds connect to a pair of T28-type ceramic turbochargers blowing in parallel through a big front-mount air-to-air intercooler. Twin blow-off valves are also fitted. Throttle response is enhanced with the RB26DETT’s six-throttle induction system and large volume log-style plenum chamber. The electronic management system uses twin hot-wire airflow meters and a set of 440cc injectors.



R33 Skyline
The RB20DET came to an end in mid 1993 it was replaced by a bigger and better version – the 2.5 litre RB25DET.



Fitted to the R33 Skyline GTS25t, the RB25DET has upsized bore and stroke dimensions compared to the older 2-litre version – bore is massively increased from 78 to 86mm and the stroke is stretched from 69.7 to 71.7mm. Interestingly, the RB25DET uses the same bore dimensions as the RB26DETT (so it’s no surprise that the heads are virtually interchangeable). The biggest difference between the RB25DET and RB26DETT cylinder head is the lifters – the ’26 uses bucket-type followers while the ’25 uses hydraulic units.

In addition to its cubic capacity advantage, the RB25DET scores larger diameter inlet runners, an improved cylinder head design, variable inlet cam timing, a larger T28-type ceramic turbo with a slightly larger intercooler and 370cc injectors. The static compression ratio is also bumped up to an aggressive 9:1 to help maintain off-boost performance.

RB25DETs are popular for tuners and, although there’s currently a good supply, these are relatively expensive engines – although they are cheaper than the more powerful RB26DETT.



The mighty RB26DETT engine was altered for use in the R33-series Skyline GT-R. A slightly improved intercooler and ECU changes (giving more mid-range boost) raised peak torque.



R34 Skyline
Released in 1998, the R34-series Skyline engines have a big emphasis on reducing emissions.

The existing RB25DET was reengineered to NEO specs, which apparently produce around one-tenth of the CO, HC and NOx emissions levels allowed under Japan’s 10-15 test mode. Further changes include a ball-bearing turbo, slightly larger intercooler, free-flow exhaust and revised ECU (which allows up to 10 psi boost).



The RB25DET NEO can be found with either a 5-speed manual or automatic gearbox with steering wheel shift buttons. Manual gearbox versions were revised in late 2000 bringing extra torque (probably through a bit of extra mid-range boost).

Meanwhile, the last-of-the-line R34 Skyline GT-R (which took until 1999 for release) received a host of engine changes. A low backpressure exhaust, altered cams, different ball-bearing turbochargers and enhanced ECU mapping are the biggest changes.



The R34 RB26DETT can be identified from the R32 and R33 versions by its red painted rocker cover. They are also fitted with a 6-speed manual gearbox.

[Mike Rapp]

Didn't realise the R33's both GTS-T and GTR are the same dimensions. Is there a big enough advantage of putting the GTR head onto the GT-ST to justify the cost? Does anyone know much about benefits to this? Sorry for the questions, still learning!

[Spearmint]

You can fit an RB26 head onto an RB25 block but at the very least you need the RB26 crank / pistons / rods etc