The Late-Model Nissan RB Guide

The twin-cam Nissan RB-series engine might be able to trace its roots back m-a-n-y years but there’s no denying this smooth in-line six is a go-fast enthusiast’s dream. They’re immensely strong, smooth, powerful and the aftermarket parts back-up is huge. It’s no wonder the RB is a favourite.

In this article we’ll examine the twin-cam turbo RB range from 1985 to its demise in 2001...

R31 Skyline

The first vehicles to use turbocharged twin-cam RB performance was the late 1985 R31 Skyline GT sedan and GTS/GTS-X coupe.

The boxy looking Skyline’s 2-litre twin-cam turbo six (RB20DET) offers tremendous smoothness along with decent torque and power. These early R31 RB20DETs (which can be identified by their ribbed red rocker cover) use an iron block with a 78mm bore and 69.7mm stroke, an 8.5:1 static compression ratio, ceramic turbine turbocharger, guard-mounted air-to-air intercooler and an alloy DOHC, 24 valve head.

The early RB20DET also uses the ‘NICS’ dual-stage twin-runner induction system (as seen here). The basic electronic management unit fires small 270cc fuel injectors and a coil-on-plug ignition system.

With standard boost pressure around 7 psi, the early R31 RB20DET generates just 132kW at 6400 rpm; it’s not a big horsepower engine. Interestingly, the same engine was available in the Japanese market Z31 Fairlady 200ZR – the only difference is the air-to-air intercooler was mounted on top of the rocker cover, as seen in this pic.

However, from late 1987, the RB20DET was upgraded to deliver 140kW and 240Nm. We’re not aware of any major mechanical differences except that the NICS dual-stage induction system was replaced with a conventional manifold wearing an ECCS tag.

The R31 R20DET comes equipped with either a 5-speed manual or 4-speed auto transmission. The engine is designed for North-South mounting and rear-wheel-drive – but be aware that these are becoming very rare.

Interestingly, there was a very limited build of R31 Skyline GTS-R coupes in late 1987. Using a tuned RB20DET-R engine (with a tubular exhaust manifold, a much larger turbo and big front-mount intercooler) these motorsport specials generate a conservatively rated 155kW. The RB20DET-R engine was commonly modified to deliver around 300kW in Group A race trim.

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.

In the R32, power is increased substantially to 158kW and there’s 264Nm of torque available at just 3200 rpm. Again, this is a very smooth engine that offers urge from about 3000 rpm.

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.

In addition to the R32 GTSt/GTS4, the silver rocker cover RB20DET was also installed to the Japanese market Cefiro and Laurel. The Cefiro (available with a 5-speed manual or 4-speed auto trans) is restricted slightly to 151kW at 6400 rpm and 265Nm at just 3200 rpm. The Laurel (which is auto only) makes the same power. All of these silver-top RB20DETs are quite easy to source at Japanese importers and they are popular for conversions into local Skylines as well as S13 Silvia/180SXs.

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.

In standard form, the R32 GT-R-spec RB26DETT delivers 355Nm at 4400 rpm and a claimed 206kW at 6800 rpm. In reality, the output is closer to around 225kW.

These are quite popular engines and most good importers will have one in stock – but don’t expect it to be cheap.

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.

From about 3000 rpm this engine really comes alive. Peak torque (a substantial 294Nm) arrives at 4800 rpm and max power is 187kW at 6400 rpm. This power output is reduced in examples with a 4-speed auto transmission – you’re looking at 180kW and 275Nm.

The RB25DET was also employed in high-performance versions of the Japanese Stagea wagon. Released in late ’96, the Stagea-spec RB25DET produces slightly less power and toque compared to the R33 Skyline version – 173kW and 275Nm. We can only assume this shortfall comes from a restrictive exhaust and air intake and a detuned ECU. The 173kW Stagea engine comes with an auto trans only and an electronic-controlled AWD system.

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 to 369Nm but, if you can believe the claims, power remained at the Japanese regulation 206kW. Something is a bit fishy there....

Note that the same RB26DETT engine tune was also used in the ultra rare Autech 260RS version of the Stagea. The R33-spec twin-turbo RB26DETT punches out 206kW/369Nm making this one of the quickest wagons in the world. As far as we can tell, the engine and gearbox are identical to the R33 GT-R’s.

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).

Fitted to the R34 25GTt, the RB25DET NEO has no problem pushing out 206kW at 6400 rpm and 343Nm at 3200 rpm - almost line-ball with the claimed output of the original RB26DETT! 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 20Nm extra torque (probably through a bit of extra mid-range boost).

As the R34-series Skyline appeared with the RB25DET NEO so did its wagon cousin – the Stagea. The second-generation Stagea (from 1998) switched from the R33 spec engine to the R34’s – you’re now talking the whole 206kW shebang.Manual, automatic, AWD and rear-wheel-drive versions were released – so take your pick!

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. These give the R34-spec RB26DETT a massive 392Nm of torque but, you guessed it, no more than 206kW. Independent testing has shown it is closer to around 240kW. 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.

These are not cheap - but, then, we’re looking at one hell of an engine!