RB25DET – Everything You Need To Know

We’re huge fans of Nissan’s RB engine, and the RB25DET is best known for being in a variety of Skylines or swapped into your favorite S-chassis. We’re looking at the pros and cons of this JDM legend.

Here, you can click on a particular section within this article. Otherwise, scroll down as we take a look at Nissan’s RB25DET engine.

• A brief history of the RB Series
• RB25DET tuning and upgrades
• Which cars have the RB25DET?
• RB25DET vs SR20DET
• RB25DET vs 1JZ-GTE
• 240SX RB25DET Swap
• Common RB25DET Issues
• Conclusion
• Additional Content

Introduction

Nissan’s RB25DET engine represents their infamous RB series, which first appeared in 1991 after replacing its predecessor – the RB20DET.

The RB25 is most commonly known for finding its home under the hood of the R33 and R34 GTS-T Nissan Skylines.

The impressive 2498cc powerplant has increased in popularity alongside its rivals over the years, with enthusiasts keen to swap it into all sorts of weird and epic builds worldwide.

The first Series 1 (S1) RB25DET engine surfaced in the 1993 Nissan Skyline R33 GTST. Improvements over the RB20 included reinforced connecting rods, and improved pistons alongside a larger 45V1 turbocharger.

The 25 featured Nissan’s NVCS VVT system on the intake side and the new larger injectors provide the engine with 370cc/min to the 250 horsepower (hp) and 235 lb-ft torque, which the engine could produce when it left the factory.

In 1995, Nissan revised their RB25DET, releasing the Series 2 (S2) engine to the market. This featured a revised electrical system and an uprated turbo, which featured a ceramic turbine wheel rather than the aluminium wheel found in the S1.

The most substantial change within the electrical system was the introduction of ignition coils, which featured built-in ignitors. Other changes included a new airflow meter, ECU, cam angle sensor, and throttle position sensor.

The only fundamental differences mechanically between the S1 and S2 are the camshafts, with the S2 Cam Angle Sensor’s shaft that goes into the exhaust cam being slightly different.

In May 1998, Nissan added the NEO head to their newly-launched RB25DET R34, mainly for emissions purposes. This enabled the R34 to be classed as a Low Emissions Vehicle due to its improved fuel consumption and emissions output.

There were quite a few changes that came with the NEO engine such as solid lifters instead of hydraulic and revised camshafts which featured on/off solenoid Variable VCT. A hotter 82°C thermostat was added along with model-specific coil packs.

A revised intake manifold was also introduced, which intentionally reduced the runner diameter from 50 to 45mm, therefore increasing the air velocity which handed the car more low-end torque.

The combustion chamber of the NEO head is smaller, and GTR-spec connecting rods compensate alongside the model-specific pistons and an increased compression ratio of 9.0:1.

The changes didn’t end there, with a larger OP6 turbocharger providing increased power, this time utilizing a steel compressor and turbine wheels. Unlike the previous nylon plastic compressor wheel and ceramic turbine wheel.

Despite focusing on the economic output to meet the LEV emissions criteria, the NEO engine also managed to earn the highest power figures of all the RB25DET engines – achieving 276 hp and 267 lb-ft torque in stock form.

The RB25DET remained the engine of choice until the final models rolled out of the factory in 2002, with the VQ25DET becoming its successor.

A brief history of Nissan’s RB Series

RB20

Initially launched in 1985, the RB20ET/DE/DET engine series engines were fitted to the HR31 Skylines and Nissan Fairlady 200ZR (Z31) and the new engine became an instant hit.

With the RB20DET eventually pushing out 212 hp, not only was it a revolutionary engine for its time, but tuners soon began to unlock its true potential.

Nissan then went on to produce several variations of the 2.0L RB:

• RB20E
• RB20ET
• RB20DE
• RB20DET
• RB20P
• RB20DET-R
• RB20DE NEO

RB24S

Little is known about the single-cam RB24S, mainly since it was extremely rare and was never produced for the JDM market, with the engine only fitted to a small number of exported LHD Cefiros.

This engine combined an RB30 head, RB25DE/DET block, and an RB20DE/DET crank. It also used carburetors instead of Nissan’s ECCS fuel-injection system.  This enabled it to rev higher than the RB25DE/DET since it has the same stroke as the RB20DE/DET but the displacement of the RB25DE/DET.

Despite its revving abilities, the naturally aspirated RB24S produced a measly 139 hp at 145 lb-ft torque. It certainly wasn’t an RB20DET killer!

RB25

In 1993, the introduction of the RB25 saw Nissan introduce three new variations to the market:

• RB25DE
• RB25DET
• RB25DET NEO

RB26DETT

Typically found in the GTR, this bigger brother of the RB25 certainly needs no introduction and is arguably one of the best engines ever made. But, in the present day, that comes at an ever-increasing price.

The RB26DETT can be found in the following cars:

• Nissan Skyline GT-R BNR32
• Nissan Skyline GT-R BCNR33
• Nissan Skyline GT-R BNR34
• Nissan Stagea 260RS WGNC34
• Tommykaira ZZII

RB26DETT N1

Nismo developed this engine for Group A and Group N motorsports after Nismo realized that the typical RB26DETT required too much maintenance for their planned cars, which were first used in the Bathurst races in Australia.

Several upgrades were carried out, including a balanced crankshaft due to the RB26DETT developing vibrations at 7-8,000rpm. They also upgraded the oil and water channels within the block alongside the pistons and rings.

There were also upgraded camshafts and three variations of the Garrett T25 turbochargers between the R32, R33, and R34 generations. R34 engines were handed the superior GT25 ball-bearing turbos.

RB28DETT

This was another rare engine built by Nismo, this time for the unicorn Nissan Skyline R34 GT-R Z-Tune. Despite using an RB26 GT500 block, it’s stroked out to 2.8L, providing an impressive 510 hp and 398 lb-ft torque straight out of the factory.

Nissan had initially hoped to do a whopping 630 hp in stock form, but due to emissions regulations, this was shelved. These figures have since become easily achievable with aftermarket support.

RB30

This engine has been the subject of many internet arguments about who manufactured it due to its use in both Nissan and Holden cars.

Nissan initially designed the RB30 for use in the R31 Skyline before Holden then purchased the rights due to their 3.3L Holden 202 failing emissions requirements, and they were forced to make a quick and drastic decision for a replacement.

Manufactured RB30s:

• RB30S (GQ Patrol)
• RB30E (R31 Nissan Skyline)
• RB30E (VL Commodore)
• RB30ET (VL Commodore)
• GTS1 RB30E (R31 Skyline)
• GTS2 RB30E (R31 Skyline)
• RB30DE (Tommykaira M30)

The RB30E in the R31 Skyline achieved just 153 hp and 186 lb-ft torque. However, the rarer GTS2 RB30E, developed by Nisan Special Vehicles Division Australia, could have 188 hp and 199 lb-ft torque.

The highest-powered factory model was the Holden-manufactured RB30ET found in the VL Commodore, capable of 201 hp, using a lower compression RB30E bottom-end and an improved oil pump, Garrett T3 turbocharger, and 250cc injectors.

These are far more common engines in the Australian region and are another excellent example of a perfect engine for a big-power drift car.

One of the rarest ever RBs is the RB30DE, found in the Tommykaira M30, based on the R31 Skyline GTS-R.

Using an uprated RB20DE head on an RB30E block, it achieved 237 hp and 217 lb-ft torque. We wish you luck if you intend to try and source one, though!

You may have heard of the RB30DET, but this was never a Nissan-produced engine. It refers to a turbocharged RB30E with a twin-cam head from another RB. Several variations can be used to achieve this since parts for the RB series are so interchangeable.

This provides the ability to achieve higher displacement than the RB26DETT. However, the RB30 lacks the RB26’s internal bracing, thus making it unstable above 7,500rpm. Enthusiasts have instead utilized the RB30’s torque potential of the longer stroke.

Some online articles show that owners have achieved 11,000rpm from RB30DET with comprehensive upgrades and balancing.

OS Giken does produce an off-the-shelf aftermarket RB30DETT kit. However, you can expect it to set you back a jaw-dropping ¥1,500,000 – around $13,500 USD!

RB25DET performance tuning and modifications

This is a hugely popular topic for all RB engines, with owners seeking to achieve their true potential.

As with all our guides, your first port of call when it comes to tuning is always to ensure that you have a healthy engine from the start. There’s nothing worse than forking out huge money on an engine that can’t deal with the power you’re planning to throw at it.

This will quickly become a VERY costly mistake unless you have a spare RB25DET lying around.

We want to mention that we don’t recommend tuning a naturally aspirated RB25DE or going through the process of strapping a turbo to your N/A. Chances are it’ll end up being far more work and expense.

With a healthy RB25DET, the typical safe figures for stock internals are around 400 hp, with some riskier owners reliably pushing them 450 hp. Some will even tell you that they are even capable of 500, but we never recommend chasing numbers unless you enjoy having to buy replacement engines. 450 hp is going to be more than enough for most purposes.

When using a stock turbocharger, we don’t recommend going beyond 0.8-0.9 bar (11.5-13psi.) If you plan to push it to 13psi, you’ll want to ensure you’re running the correct supporting mods.

This typically includes an upgraded exhaust system, a front mount intercooler, an intake, Z32 MAF, induction kit, and you’ll also need a boost controller.

On top of that, other recommended mods are an uprated fuel pump, oil pump, and oil cooler. You’ll also need an aftermarket ECU. This should provide you with around 300 hp.

From there, you’ll need to consider upgrading your turbo, injectors, fuel pressure regulator, radiator and coils, etc.

This should be a rough package to make 400 hp achievable.

If you’re hoping for 500 hp, expect to upgrade the camshafts, bigger valve springs, and fuel injectors. Beyond that, GTR rods, forged pistons, uprated head gasket, ARP studs, and head porting must be on your agenda.

If you plan to go full retard, you can source an RB26DETT head and one of the off-the-shelf stroker kits to achieve a displacement of around 2.8-2.9L.

As you can see, tuning is never cheap, and it’s always better to be safe than sorry by fitting reputable parts to ensure the best reliability and the smallest chance of problems possible.

If HUGE power figures are your goal, we highly recommend considering an RB26DETT swap to be on the safer side.

Which cars came with the RB25DET?

• Nissan Skyline R33/R34 GTST
• Nissan Stagea WC34
• Nissan Cedric Y34
• Nissan Gloria Y33 & Y34
• Nissan Laurel C34 & C35

RB25DET vs SR20DET

If you look at the displacement, this may seem like an unfair comparison. However, there are advantages and disadvantages to using both these engines, which are commonly used for swaps.

Firstly, one of the advantages of the SR20DET over the RB25DET when it comes to s-chassis swaps, perhaps for your 240SX, is that the 4-pot SR20 is around 80kg lighter, which is excellent for weight distribution and handling.

If big power is your intention, perhaps for drag racing and even possibly drifting, then the RB25DET will most likely be the better choice due to its powerful capabilities.

For drifting, the weight distribution of the SR will most likely be far easier to work to your advantage, depending on what you’ll be swapping it into.

That said, if you intend to reach beyond 350 hp, then the RB may be the more efficient choice. SRs can achieve bigger power figures than this, but it quickly gets costly, whereas RBs can achieve 500 hp far easier.

If you already have an SR and you’re considering swapping for an RB25DET, chances are that by the time you’ve spent the money on the swap, you’ll be left with a 260 hp engine when you could have a 350 hp SR with far more torque for the same cash.

Both have their advantages and realistically it all comes down to personal preference and whether you have a spare engine lying in the garage!

RB25DET vs 1JZ-GTE

Think of these as the little brothers of our RB26DETT vs 2JZ-GTE debate. This is the battle between two of the most popular 2.5L 6-cylinder engines.

Both engines are very similar in size, with roughly the same bore and stroke, and the head stud and bearing thickness are also roughly the same.

This video showing the testing of two randomly sourced blocks was insightful for this topic, which may sway your opinion slightly:

We’re going to be brutally honest and say that the chances are, given the circumstances, we would be opting for the 1JZ on this occasion.

The RB25DET would require quite a substantial chunk of cash being thrown at it before it can achieve similar figures as the 1JZ is capable of if you’re looking at considerable power since the 1JZ has often been seen reliably running 600 hp+ on stock internals.

Like for like, the 1JZ, from our experiences, would also win the reliability argument overall.

That said, both are excellent engines and if you can get your hands on either one, you certainly won’t be disappointed!

Oh, and both engines sound damn sexy too!

240SX RB25DET Swap

This has become a common swap, especially for KA owners. Given its popularity, many off-the-shelf parts have been produced to make the swap easier than ever.

Here are a few basic essentials to get yourself on your way to your new big-power setup!

Engine Mounts

“The ISR Performance RB swap mounts are designed to be your one-stop solution for all RWD Nissan RB series engines using the RB20 or RB25 RWD Transmission to fit S13 and S14 chassis.”

Purchase the ISR Performance RB Swap Mounts for Nissan 240sx at Enjuku Racing.

Driveshaft

“This is a complete 6061-T6 aluminum shaft that is about 1/2 the weight of the factory 2-piece. The shaft features larger, replaceable and greaseable u-joints and can handle about 650 whp. By removing the factory 2-piece shaft and installing a single shaft the car will feel more responsive due to the fact the hanger bearing is not moving up and down during acceleration. Available for most popular motor/trans combinations, if you don’t see yours listed, custom shafts are also available.”

Purchase the ISR Aluminum Driveshafts at Enjuku Racing.

Wiring Harnesses

“If you’re looking to save some serious time and cash by replacing both your engine and transmission harnesses, look no further. This plug-and-play is for the RB25DET installed in a S13 240SX and requires no additional wiring. The handy premade RB25 S13 swap combo makes replacing both harnesses fast, easy, and affordable.”

Purchase the 240SX Non-NEO Wiring Harness at Enjuku Racing.

Purchase the 240SX NEO Wiring Harness at Enjuku Racing.

Common RB25DET Issues

RBs are generally well-known for their reliability and durability. However, all cars have issues, eventually, and given the age of these engines now, it should come as no real surprise.

They’ll serve you exceptionally well when treated right using the correct service intervals and high-quality lubricants. There are no reports of any significant design flaws, which would’ve undoubtedly surfaced by now!

One of the most concerning issues is circuit racing, drag or drift RB25, which are generally pushed to or beyond their limits for prolonged periods. In this case, owners find excess oil in the cylinder head and catch can but not enough oil in the sump.

Several possible solutions include fitting an external oil return from the rear of the cylinder head to the sump. However, if you’re experiencing these problems, it’s well worth looking into all of the recommendations to see which ones apply to your specific case.

Oil surge can cause bearing failure if people overfill. This often happens during track use when owners have filled up to the ‘H’ on the dipstick, which is around 10 mm over the ‘full’ line.

Running more than 0.9 bar of boost on a standard turbo will undoubtedly cause premature turbo failure, so we highly recommend against doing so.

Fitting an oil cooler is recommended, especially in hotter areas or for those that like to push the car. Either way, it’s suggested that you keep a close look at the oil temperatures when driving hard.

Minor problems include failing ignition coils, which can cause misfires, but swapping out the coils is an easy enough fix, and it’s recommended to do them every 60,000 miles anyway.

Additionally, the cam angle sensors do have a habit of causing issues from time to time. There are many solutions to the problem online, but swapping it out is typically the best choice.

Other than that, we have heard of various reports of electronic issues, as with all cars! However, given the age and how some are treated, it hardly comes as a surprise and could boil down to absolutely anything.

Overall, the RBs are generally highly reliable engines, and a healthy powerplant will undoubtedly be more than happy to provide you with durability up to 400hp on stock internals.

Conclusion

There are many valid reasons why the RB engine series is so highly regarded in the tuning scene and across the entire automotive world.

If you’re considering an RB, not necessarily the RB25DET, then we do not doubt each one will serve you well.

If weight is an aspect of your decision, it may be worth looking into the RB20DET rather than completely ruling it out. These are lightweight, cheap, bulletproof engines with excellent tuning potential and enjoy being revved more than RB25s – great for drifting!

If HUGE power numbers are your aim, the RB26DETT must be seriously considered. Sure, the RB25DET is capable of big numbers, but the RB26DETT is the better choice if you’re starting from scratch unless you’re being handed a free RB25DET!

If money is no issue, you may even consider going down the RB28DETT route for the additional rarity factor!

There will always be superior engines on the market, but the RB25DET has certainly earned a worthwhile spot in the history books.

Even though Toyota lovers will continue to voice their opinions on the 1JZ (or 2JZ), we do not doubt that the RB25DET will be more than capable of putting a huge smile on your face for many years to come!

Additional RB25DET Related Content

We’ve selected some of our favorite RB25DET YouTube picks for viewing!

This 280Z with a 535 hp RB25 is a match made in heaven!

We never get bored of sound compilation videos!

Check out this awesome and informative 700 hp+ 240SX conversion.

The world’s fastest unstroked RB25 heads to the drag strip to lay down a 9.9 sec 1/4 mile (later beating it with 9.7 sec).

Patrol? Check. Wheelies? Check!

RB25 Hakosuka. This is what dreams are made of!

Kevin Lawrence explains everything there is to know about RBs in this comprehensive video:

Adam LZ gets help from Kevin Lawrence with building his RB25DET in this insightful teardown video.

Still not sure which RB engine is going to be best-suited for your needs? Check out this comparison video, where the RB heavyweights go head-to-head.

Photography credits

Drifted would like to extend thanks to the following sources for the use of their images:

• Dream Fotographie (Eric de Jong)
• Vic Z Car on viczcar.com
• Wikipedia
• Wangan Warriors
• William Lee (Flickr)
• Alessandro Renda (Flickr)
• Kevin Saengsourinho (Flickr)
• RBS14K (Flickr)
• Enjuku Racing

Learn everything that you need to know about Nissan’s RB20DET engine here!

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