Twenty years of oversquare straight-sixes, from the 1985 RB20 to the twin-turbo RB26DETT that made the Skyline GT-R a legend.
The Nissan RB is a straight-six petrol engine family built from 1985 to 2004 in capacities from 2.0 to 3.0 litres. It came in SOHC and DOHC forms, with turbo and non-turbo variants, and its best known model is the RB26DETT twin-turbo fitted to the Skyline GT-R.
Few Japanese engines have a following as loyal as the Nissan RB straight-six. Over two decades the family grew from a 2.0 litre twin-cam to a 2.6 litre twin-turbo, and it remains a platform that tuners still favour for the Skyline GT-R.
When was the RB engine introduced?
The RB is an oversquare 2.0 to 3.0 litre straight-six four-stroke petrol engine from Nissan, produced from 1985 to 2004. It followed the 1983 VG-series V6 engines and gave Nissan a full, modern range in both straight and V layouts. It belonged to a family name called PLASMA, which stood for Powerful and Economic, Lightweight, Accurate, Silent, Mighty and Advanced.
The RB was derived from the six-cylinder L20A, which shares its bore and stroke with the RB20. That link meant the new family could reuse proven geometry while adding the features that the late 1980s market expected.
Every RB engine was made in Yokohama, Japan, the same plant that built the VR38DETT. Nismo, Nissan's motorsport division, rebuilt some RB engines at its Omori Factory in Tokyo, and every Z-Tune Skyline was rebuilt there.
Twenty years of straight-six engineering that gave the Skyline GT-R a twin-turbo engine and a racing pedigree.
How were RB engines built?
The family included single overhead camshaft (SOHC) and double overhead camshaft (DOHC) engines. Both types had an aluminium head and a cast iron block, and each cam lobe moved only one valve. SOHC versions had two valves per cylinder, while DOHC versions had four.
All RB engines used belt-driven cams. Most turbo models had an intercooled turbo, and the single-cam RB20ET and RB30ET were the exceptions. Most turbo models also carried a recirculating factory blow-off valve, which reduced compressor surge when the throttle closed quickly.
Nissan also used a letter code to describe each engine. A D indicated a dual overhead cam, an E indicated electronic fuel injection on a single cam, and an S indicated a carburettor. T meant a factory turbocharger, TT meant twin turbochargers, and P meant the engine ran on LPG.
What were the stock RB dimensions?
Each RB engine's displacement came from its bore and stroke, and the naming convention reflected that size. The table sets out the stock dimensions for the five main RB capacities, which are the starting point for most rebuilds and stroker projects.
| Engine | Displacement | Bore | Stroke |
|---|---|---|---|
| RB20 | 2.0 L (1,998 cc) | 78 mm (3.07 in) | 69.7 mm (2.74 in) |
| RB24 | 2.4 L (2,428 cc) | 86 mm (3.39 in) | 69.7 mm (2.74 in) |
| RB25 | 2.5 L (2,498 cc) | 86 mm (3.39 in) | 71.7 mm (2.82 in) |
| RB26 | 2.6 L (2,568 cc) | 86 mm (3.39 in) | 73.7 mm (2.90 in) |
| RB30 | 3.0 L (2,962 cc) | 86 mm (3.39 in) | 85 mm (3.35 in) |
The 86 mm bore is shared by the RB24 to RB30, which is why the RB25 and RB26 can take parts from each other. The RB20 has a smaller 78 mm bore, so its heads and pistons do not swap across the range.
What were the RB20 variants?
The RB20 was the first member of the family to reach production. The RB20ET, DE and DET were fitted to the HR31 Skyline and the Fairlady 200ZR from August 1985, while the RB20E had gone into the C32 Laurel from October 1984. Each version used different injection and cam arrangements.
The early twin cam engines used the NICS injection system, while later versions switched to the ECCS engine management. Later ECCS versions replaced the twelve tiny runners of the earlier intake with six much larger ones, though the head kept twelve ports, which meant a splitter plate was needed.
The RB20DE made 110 to 114 kW (148 to 153 hp; 150 to 155 PS) at 6400 rpm, while the turbocharged RB20DET made 158 kW (212 hp; 215 PS) at 6400 rpm. The RB20DET-R, fitted to the Skyline 2000GTS-R (HR31), was rated at 210 PS (154 kW; 207 hp) and was limited to 800 units.
The second series of RB20E, DE and DET engines ran from 1989 to 1993 in the Laurel, R32 Skyline and Cefiro. They used an improved head and the ECCS system, and enthusiasts know them as Silver Top engines.
What made the RB24S unusual?
The RB24S was a comparatively rare engine, because it was not produced for the Japanese domestic market. It was fitted to some left hand drive Cefiros exported new from Japan, and it combined an RB30E head, an RB25DE/DET block and an RB20DE/DET crank with 34 mm height pistons.
It used carburettors rather than Nissan's ECCS fuel injection. Because it shared the stroke of the RB20DE/DET, it could rev higher than the RB25DE/DET, and it displaced almost the same. The standard single cam form made 141 PS (139 hp; 104 kW) at 5,000 rpm and 197 Nm (145 lb ft) of torque at 3,000 rpm.
How did the RB25 develop?
The RB25 series was first introduced in the R32 Skyline GTS25 sedan and coupe in 1991. The RB25DE was naturally aspirated and the DET was turbocharged, and both gained NVCS (Nissan Variable Cam System) on the intake cam from August 1993. That gave the newer RB25DE more power and torque at lower revs.
Series 2 engines arrived in 1995 with a revised electrical system. The RB25DET(S2) turbocharger used a ceramic turbine wheel instead of aluminium, and ignition coils gained built-in igniters. Mechanically, the series 1 and series 2 were very similar, with the camshafts being the main difference.
In May 1998 a NEO head was fitted, which allowed the engine to be classed as a low emission vehicle engine. The NEO head used solid lifters, revised camshafts with higher lift and shorter duration, and a smaller combustion chamber that needed model-specific pistons to compensate.
The RB25 was produced in four main forms. The RB25DE was rated at 180 to 200 hp (134 to 149 kW; 182 to 203 PS), while the RB25DET reached 245 to 250 hp (183 to 186 kW; 248 to 253 PS). The RB25DE NEO made 197 hp (147 kW; 200 PS) at 6000 rpm, and the RB25DET NEO reached 276 hp (206 kW; 280 PS) at 6400 rpm.
What is the RB26DETT?
The RB26DETT is a 2.6 litre twin-turbo inline-six built for the 1989 to 2002 Skyline GT-R. Its cast iron block and aluminium DOHC head carry four valves per cylinder, giving 24 valves in total, and its intake uses six individual throttles set in three siamesed pairs instead of one throttle body.
The engine uses a parallel twin-turbo system with a pair of T25-type ceramic turbochargers. The wastegates limit boost to 10 psi (0.69 bar), and the Skyline GT-R also has a built-in boost restrictor that keeps boost under 14 psi (0.97 bar).
Nissan first rated the RB26DETT at 276 bhp (280 PS; 206 kW) at 6,800 rpm, with 353 Nm of torque. Power later rose to about 320 PS (235 kW; 316 hp) at 6,800 rpm, with 392 Nm at 4,400 rpm. Enthusiasts have long believed the true output was closer to the higher figure.
The gap between the two figures came from an informal limit. A gentlemen's agreement between automakers capped advertised horsepower at 280 PS, so the official rating stayed at that level even as the engines improved. The RB26 earned a name for its strength and its iron block and forged internals, which made it a popular base for tuners.
Several factory features set the RB26DETT apart. These included solid lifters with shims under the bucket, belt-driven cams, a crank angle sensor driven from the exhaust cam, cooled oil pressure lubrication for the turbos, cooling channels under the piston crowns, piston oil squirters, sodium-filled exhaust valves and an eight counterweight crankshaft.
Pre-1992 R32 RB26 engines had a known oiling problem. The surface where the crankshaft met the oil pump was machined too small, which could lead to oil pump failure at high rpm. Later series used a wider oil pump drive, and aftermarket collars and spline drive solutions were developed for older engines.
The R34 generation brought ball bearing T28 turbochargers in place of journal bearing units, and the R34 GT-R kept the ceramic exhaust turbine wheel. Other R34 changes included candy red cam covers, a plastic cam gear cover, Hitachi crank angle sensor drive, built-in igniters in the coil packs and a dual mass flywheel.
What were the RB26DETT N1 and Z-Tune engines?
The RB26DETT N1 was developed by Nismo for Group A and Group N motorsport. Nismo found the standard engine needed too much maintenance for racing, so it designed an N1 block, which was first used at Bathurst in Australia. The N1 also had a balanced crankshaft, improved water and oil channels, and upgraded camshafts and turbochargers.
The N1 turbochargers used steel turbine wheels instead of the ceramic wheels of the standard engine, because ceramic was found to be unreliable at high speeds and higher boost. The N1 block used an 86 mm bore that could be bored to 87 or 88 mm, and it was cast with the mark 24U, while the standard block carries 05U.
The RB26DETT Z1 and Z2 engines powered the Skyline GT-R Z-Tune built by Nismo. They used a stronger RB26 block, a stroked crankshaft and upgraded turbochargers, and they reached a displacement of 2.8 litres. The Z1 produced 500 PS (368 kW; 493 hp) and 540 Nm (400 lb ft) of torque.
The Z2 revision added turbochargers supplied by IHI and further changes that let the engine reach up to 8,000 rpm. Nismo's Omori Factory rebuilt the Z-Tune engines, as it did every Z-Tune Skyline.
How did the RB30 engines serve Holden and Nissan?
The RB30 was produced from 1985 to 1991 in several forms. The carburetted RB30S powered GQ Patrol models at 100 kW (134 hp; 136 PS) at 4,800 rpm, while the fuel-injected RB30E was rated at 114 kW (153 hp; 155 PS) at 5,200 rpm in the VL Commodore.
Nissan sold the RB30E to Holden for the VL Commodore after Holden's 3.3 litre engine could no longer meet tightening emissions rules. Holden branded the engines Powertech 6Ei and Powertech 6EiT for turbo applications, and the names appeared mainly in its own videos and brochures.
The turbocharged RB30ET produced 150 kW (201 hp; 204 PS) at 5,600 rpm and was found only in the VL Commodore. It used a lower compression RB30E bottom end, a more powerful oil pump, a knock sensor and a Garrett T3 turbocharger, and it is still popular in Australian and New Zealand drag racing.
Nissan Special Vehicles Division Australia built two limited R31 Skyline models. The GTS1 made 130 kW (174 hp; 177 PS), and the GTS2 reached 140 kW (188 hp; 190 PS), both with longer opening duration cams and better flowing exhausts.
Tommykaira's RB30DE used a modified head on the RB30E block. In the R31 M30 it delivered 177 kW (241 PS; 237 hp) at 7000 rpm, and the later R32 M30 version enlarged the bore to 87 mm and reached 3030 cc, producing 206 kW (280 PS; 276 hp) at 7200 rpm.
The RB30DET was a hybrid rather than a Nissan engine. It used an RB30E short block with a twin-cam head from another RB engine, which gave a compression ratio of around 8.2:1. That suited a moderately modified street turbo, and it was a common hybrid in Australia and New Zealand.
What were the RB28 and stroker options?
The RB-X GT2, designed and built by REINIK for the NISMO 400R, was bored and stroked to 87 mm by 77.7 mm, giving 2,770 cc. It produced 450 PS (444 hp; 331 kW) at 6800 rpm, and it competed at Le Mans, Pikes Peak and in other motorsport.
REINIK also built more than 20 RB28DET engines based on the R33 RB25DET for a special edition R33 GT25t called 280 Type-MR. Those engines were limited to 300 PS (296 hp; 221 kW) and were built for high torque.
Many stroker kits are available for RB engines. Achievable displacements include 2.2 and 2.4 litres for the RB20, 2.6 to 2.8 litres for the RB25, and 2.7 to 3.4 litres for the RB26, while the RB30 can reach 3.2 to 3.4 litres.
Frequently asked questions
How much power did the RB26DETT make?
The first rating was 276 bhp (280 PS; 206 kW) at 6,800 rpm. Later versions were rated at about 320 PS (235 kW; 316 hp) at the same speed, and enthusiasts often say the real output was closer to that higher figure.
How many RB20DET-R engines were built?
The RB20DET-R was fitted to the Nissan Skyline 2000GTS-R (HR31) and was limited to 800 units. It was rated at 210 PS (154 kW; 207 hp) at 6400 rpm.
Which vehicles used the RB26DETT?
The RB26DETT was used in the Skyline GT-R BNR32, BCNR33 and BNR34, the Autech BCNR33 40th Anniversary model, the Stagea 260RS WGNC34 and the Tommykaira ZZII concept car.
What is the Z-Tune Skyline engine?
The Z-Tune used an RB26DETT Z1 or Z2 engine built by Nismo at 2.8 litres. The Z1 made 500 PS (368 kW; 493 hp) and 540 Nm, and the Z2 added IHI turbochargers and a higher rev limit.
Is the RB30 related to the RB26?
Yes, in a limited way. The RB30 block lacks the RB26 block's internal bracing, so it cannot rev as high, but some RB30 blocks can be fitted with RB26 cylinder heads and turbo parts.
