Nissan RB20 vs RB25: Which One is Better? 

The Nissan RB engines continue to topple other series of machines with their capability and engine performance that have been proven to be great, especially in a different driving style of drifting. Much has been used to fit such purposes and pushed these engines to their utmost potential. The two have always been the better engines among their competition in terms of reliability, price, power output, and engine performance.

Join me as we discuss the Nissan RB25 and RB26 engines and their core difference which makes them unique; and which is better than the other.

Let’s get right to it!

The Nissan RB20 Engine:

  • Production Run: 1984 – 2002
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Cast-iron
  • Configuration: Straight-six
  • Bore: 78 mm
  • Stroke: 69.7 mm
  • Valvetrain: SOHC two valves per cylinder and DOHC four valves per cylinder
  • Displacement: 2.0 L (1998 cc)
  • Compression Ratio: 8.5
  • Weight: 580 lbs.
  • Maximum HP: 212 HP at 6,400 RPM
  • Maximum Torque: 195 lb-ft at 3,200 RPM

The Nissan RB20 engines are the first machines to be fitted on the Nissan Fairlady 200ZR and the HR31 Skyline, produced from Mid-1985. It comes in two cam releases, with the early twin cam engines features the Nissan Induction Control System Injection system (NICS). In contrast, the succeeding twin cam engines used an Electronic Concentrated Control System (ECCS). Later models that used ECCS engine management obliterated the small twelve runners and replaced them with larger ones – but they retained twelve ports on the head, hence a splitter plate. It also powered the A31 Cefiros, C32, and C33 Laurel. The Fairlady 200ZR is installed with an inter-cooled RB20DET.

The engine was based on the framework of the L20A engine. It has a cast-iron cylinder block and aluminum cylinder heads. The cylinder bore diameter is 78 mm; piston stroke is 69.7 mm, and a compression rating of 8.5.

The RB20 engine has seven variations under its name. And the first engine to come out in an RB20 name is the RB20E used in the C32 Nissan Laurel, produced in late-1984. R32 Skylines, Laurels, and Cefiros used the 1989 – 1993 release as their engines with an improved head design, more commonly known as the ‘Silver Top’ engines.

The variations of the RB20 engine consists of:

RB20E is the first release and features a single cam that can produce up to 14 HP at 5,600 RPM and 133 lb-ft of torque at 4,400 RPM. A turbocharged version, RB20ET, was followed right after the release of RB20E, which is also a single-cam but has a higher power production at 168 HP at 6,00 RPM and 152 lb-ft of torque at 3,200 RPM.

Nissan produced a twin-cam RB20 called RB20DE that can produce 153 HP at 6,400 RPM and 137 lb-ft of torque at 5,600 RPM. A turbocharged version, RB20DET, of the same variant was also made that has a maximum power production of 212 HP at 6,400 RPM and 195 lb-ft of torque at 3,200 RPM. It also has a variant named RB20DET-R with a peak power of 207 HP at 6,400 RPM and 181 lb-ft of torque at 4,800 RPM.

A 12-valve, single-cam, autogas LPG powered engine badged as RB20P was rated at 93 HP at 5,600 RPM and 105 lb-ft of torque at 2,400 RPM. And lastly, a twin-cam NEO variant was made for a lesser emission and can produce 153 HP.

The Nissan RB25 Engine

  • Production Run: 1991 – 2001
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Cast-iron
  • Configuration: Inline-6
  • Bore: 86 mm
  • Stroke: 71.7 mm
  • Valvetrain: DOHC four valves per cylinder
  • Displacement: 2.5 L (2498 cc)
  • Compression Ratio: 10
  • Weight: 507 lbs.
  • Maximum HP: 250 HP at 6,400 RPM
  • Maximum Torque: 188 lb-ft at 4,000 RPM

The Nissan RB25 is the initial engine made from the RB series that was designed as a non-turbo twin-cam machine and part of the most revered RB series of engines that powered the legendary powerhouse Nissan Skyline GTST R33. The RB25 engine is the newer rendition and much-improved package over its predecessor RB20DET.

The RB25 is a straight-six, 2.5 Liter, non-turbocharged engine, famous for being in the skyline series, and it debuted in the R32 Nissan Skyline GTS25 sedan and coupe models. It is badged as the RB25DE engine. It is a non-VCT (variable valve timing and lift) and can produce up to 190 HP at 6,000 RPM and 183 lb-ft of torque available. Two years since its emergence, it would go on to form four iterations to present in the market: RB25DE, RB25DET, RB25DE NEO, and RB25DET NEO.

RB25 engine used the same cylinder block as its predecessor in RB20, as we mentioned above. It is made from cast iron with a larger cylinder bore diameter of 86 mm, piston stroke of 71.7 mm, and a compression rating of 8.5, along with new connecting rods and pistons.

The cylinder head is made out of an Aluminum alloy with two camshafts with four valves per cylinder – two on both intake and exhaust, unlike the RB20, which has a SOHC and DOHC variation. Early RB25 models, especially those produced before 1993, are not equipped with the variable valve timing system (NVCS) – which the RB25DE engine is a part of.

Moving on, sometime in 1993, the first-ever RB25DET series (S1) appeared on the 1993 Nissan Skyline R33 GTST, which featured Nissan’s NVCS VVT system (Variable Valve Timing) on the intake side. That addition gave this engine a boost in power and torque production at the lower-end RPM range than its previous model. It has new pistons, reinforced connecting rods, a 45V1 turbocharger, and a larger fuel injector that provides the engine with 370 cc/min of fuel. RB25DET S1 can produce 250 HP at 6,400 RPM and 235 lb-ft of torque at 4,800 RPM in its stock form.

Two years after the Series 1 was released, in 1995, Nissan upgraded the S1 and restyled both previous models – RB25DE and RB25DET, to join the market release of the second series (S2). This alteration featured a new 45V2 turbocharger with a ceramic turbine wheel contrary to the previous ones that use Aluminum. But the most apparent change in this version is its revised electrical system, where ignition coils feature built-in ignitors. Some modifications include a new airflow meter, cam angle sensor, mass airflow sensor, throttle position sensor, crankshaft position sensor, and ECU.

Three years later, Nissan modified the engine, they put a different head to the newly-launched RB25DET R34 and named it RB25DET NEO; NEO stands for Nissan Ecology Oriented. Hence the engine’s primary goal is to minimize the emissions as it is a complaint to higher ecological standards, which enabled the R34 to pass as a Low Emission Vehicle with better fuel consumption and lesser emission outputs.

The changes and additional features that came with the RB25DET NEO models include solid lifters instead of the typical hydraulic lifters. These revised camshafts have turn-on and off solenoid Variable VCT, RB26DETT connecting rods, and model-specific coil packs along with a hotter 180F thermostat.

Nissan also adjusted the intake diameter with a reduced runner diameter from 50 mm to 45 mm. Two inlets are made for the manifold, increasing the air velocity going into the engine, giving the machine a more lower-end torque action. NEO head combustion chambers are smaller, so Nissan used a model-specific modified piston to compensate to go with the GT-R connecting rods, resulting in an increased compression rating of 9.0.

The RB25DET NEO engine uses a 45V3 turbocharger with a larger OP6 turbine which has a steel compressor and a ceramic turbine wheel. This turbocharged engine was upgraded, and Nissan placed a larger exhaust housing and a significant increase in power.

Even though these engines are primarily made for ecological compliance to meet the LEV criteria, the NEO version has outstanding power output. It earned one of the highest figures of all RB25DET engines, producing 250 HP at 6,400 RPM and 267 lb-ft of torque in stock form.

Engine Potential:

In terms of internal component reliability or its tuning potential, the RB25 engine can reach the 500 HP with the correct replacements. To add to that, the internals of the RB25 engine can withstand high power production hence the ability to attain elusive power marks. It does not have an issue with its torque production since the RPM range can cater to different driving conditions.

That is not the case for the RB20 since some others report that the engine lacks decent torque below the 4,500 RPM range. That can be fixed, though, and you can also throw in turbochargers to boost the power production that can attain 360 HP tops.

Aftermarket support is excellent for both engines as the aftermarket items you need will not be lacking or hard to find, such as the camshafts and turbochargers.

Problems Surrounding the Engines

Nissan RB25 engine, apart from electronic problems and high fuel consumption, does not have serious issues that may affect the engine’s performance. But one notable issue that might be overlooked sometimes is the premature turbo failure caused by hyperextending the maximal boost pressure of the turbo. Pushing the boost pressure way beyond the critical rating will pose some risk to the turbo and engine.

On the other hand, RB20 engines also have issues regarding its oil system as well as ignition coils that cause an engine misfire.

Most issues revolve around external factors and not engineering design flaws.

Summary

If you are looking for a drift or project car that is cheap and beginner-friendly, RB20 might be fit for you. It can produce good power with minimal modifications and is less expensive than the RB25. Swapping is much easier and can reach 8k revving on the stock valve train. However, torque-wise, RB25 is far superior to the RB20, and its ceramic-wheeled turbo makes it weaker than the RB25.

RB25s have good potential; they can reach 500 HP on stock internals and has a powerful transmission. But the price tag for the RB25 is relatively high as its parts are becoming rare therefore more expensive. Its turbo, fortunately, is better than RB20 since it used a steel wheel.

Overall, both are reliable engines, but RB25 is better at torque and power production as well as solid transmission. But if you are starting a project car and do not have that huge amount, RB20 can really be a good engine; since it has a good gas mileage, and you don’t need upgrades for it to be that strong. Suitable for those who want a competitive but cheaper drifting alternative.

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