Nissan RB20DET Engine Guide

Initially introduced in 1985, the Nissan RB20 series of motors has a long and storied history. Though they are not as popular as their bored out RB25 and RB26DETT siblings, the RB20 motors are still very capable. Probably the most sought out of the RB20s are the RB20DET and the ultra rate RB20DET-R engines. Nissan put the RB20DET in the Skyline from the mid-’80s to the early-’90s, while the R type was only available for a few months in 1987. For many years, the RB20DET was one of the top dogs for Nissan performance, producing just over 210 horsepower, stock.

This guide is here to cover everything you need to know about Nissan’s RB20DET engine and its variants. We’ll look briefly at the engine’s history, before digging into the technical specs, car applications, engine specs, common problems, and most importantly, performance and mods.

Engine History

The RB series is the successor to Nissan’s L-series engine. In 1985, Nissan released the first engines in the RB20 series, and these included both naturally aspirated and turbocharged variants. The naturally aspirated variant was labeled the RB20DE, while the turbocharged variant was the RB20DET. There were also the RB20E, RB20ET, RB20P, RB20DET-R, and the RB20DE NEO variants.

Nissan first put the RB20DET in the 1985 Skyline GT/GTS/GTV/GTE (R31) and 1985 Fairlady Z 200ZR (Z31). The engine made between 180-190 horsepower, depending on the model Nissan put it in. Later, Nissan put the RB20 turbo in the Laurel and Cefiro models, too.

While Nissan ended production on the RB20DET in 1993, after introducing its successor the RB25DET, other variants still lived on. The RB20E lasted the longest, and Nissan still had it in production as late as 2002 in the Nissan Crew LS/LX.

Technical Specifications

Engine	RB20DET
Model Years	1985-1993
Displacement	2.0 L (1,998 cc)
Aspiration	Turbocharged
Configuration	Straight-Six
Compression Ratio	8.5:1
Bore and Stroke	78 mm × 69.7 mm (3.07 in × 2.74 in)
Valve Train	DOHC, 4v/cy; 24 Valve Total
Fuel System	Electronic Fuel Injection (EFI)
Head/Block Material	Cast Iron
Horsepower Output	180-215 horsepower
Torque Output	180-195 ft-lb of torque

Car Applications

RB20ET (170 horsepower)

• 1985–1989 Nissan Skyline GT (R31)

RB20DET (180-215 horsepower)

• 1985–1993 Nissan Skyline GT/GTS (R31; R32)
• 1985–1989 Nissan Fairlady Z 200ZR (Z31)
• 1988–1994 Nissan Cefiro (A31)
• 1988–1993 Nissan Laurel Medalist (C33)

RB20DET-R (205 horsepower)

• 1987 Nissan Skyline GTS-R Coupe
  • Only in production from May-November
  • Only on sale from August-September in Japan
  • 823 produced total, 4 of them prototypes

Engines Specifications

All of the engines in the Nissan RB20 series have straight-six configurations. The Nissan RB20 block and cylinder head are both made from cast iron, and the bore and stroke are 78 mm × 69.7 mm (3.07 in × 2.74 in). The engine code can be broken down as follows: RB – “RB” engine series; 20 – 2.0 liter displacement; D – Dual Overhead Camshafts (DOHC); E – Electronic Fuel Injection; T – Turbocharged.

Most of the RB20 series has a DOHC twin-cam valve train, with 4 valves per cylinder for 24 valves total. RB20 engines without the DOHC valve train are OHV with pushrods and only 12 Valves.

Nissan RB20E and RB20ET Engine Specs

Nissan created the RB20E as the first engine in the series, and it only made between 110-130 horsepower. The RB20E is an OHV pushrod engine, with 2 valves per cylinder, for 12 total, and has a short stroke crank.

Nissan also created a turbocharged version, the RB20ET, which bumped power up to 145-170 horsepower. It ran 7 PSI of boost and did not have an intercooler. All RB20E/T have a static compression ratio of 9.5:1.

Nissan RB20DET Engine Specs

The turbocharged variant is the RB20DET, and it has lower compression at 8.5:1 to accommodate the boost. The turbo is a 16V turbo with a T3 flange and runs 7 PSI of boost. The connecting rods, pistons, crankshaft, head gasket, 270cc fuel injectors, and ECU were all different from the RB20DE.

The RB20DET from 1985-1987 is known as the Redtop model due to the red-colored valve cover. These models had the Nissan Induction Control System (NICS). The NICS had a twin-runner design, with 12 individual runners for the six cylinders and used a coil-on-plug ignition system. The NICS intake manifold also uses a dual-stage induction system for better low-end torque.

The Redtop cams had duration of 240° intake, 240° exhaust; 248° intake, 240° exhaust. The cams lift is 7.3mm intake, 7.8mm exhaust; 7.8mm intake, 7.8mm exhaust. These early Redtops made 180-190 horsepower and came with air-to-air intercoolers.

Released in 1988, the Silvertop RB20DET switched to Nissan’s Electronic Concentrated Control System (ECCS) with a revised manifold. Most of the engine stayed the same, but a larger turbo was fitted and the ECU changed. Nissan rated the new Silvertop RB20DET at 215 horsepower, a healthy 20-30 horsepower bump.

The Ultra-Rare RB20DET-R Variant

Nissan very briefly released the RB20DET-R variant in 1987 specifically for the Skyline GTS-R coupe. Nissan specifically made this to compete under FIA rules in competition racing. Basically, the FIA changed some of the regulations for the 1987 season for “Group A” racing, but realizing that not all manufacturers would implement the changes so quickly into production models, they only required 500 “homologation” vehicles to be built that reflected the changes in order to compete that season.

500 sounds like a lot, but it was actually a substantial decrease from the normal 5,000 needed previously for homologation. Nissan specifically built the Skyline GTS-R – with the RB20DET-R – to compete in the 1987 season under FIA regulations. Since Nissan only needed to produce 500 models, production only lasted from May-November in 1987, and Nissan only made 823 total, including 4 prototypes.

They were only offered on sale from August-September in Japan, and are probably the rarest Skyline engines ever. It is similar to the standard RB20DET, but made about 205 horsepower (the normal RB20DET made 180-190 horsepower still) due to a larger T04E turbo, new tubular equal-length exhaust-manifold, unique dump pipe, larger throttle bottle, lightened flywheel, and a bigger and front mounted intercooler. The FIA competition racing versions made north of 400 horsepower.

RB20DET vs RB25DET vs RB26DETT Engines

The RB20DET is commonly compared with its larger siblings, the RB25DET and RB26DETT. The RB25DET has a larger turbocharger, while the RB26DETT has twin-turbos. Of the three, the RB20 is by far the most underpowered and least sought out. It is still a popular option for swaps, especially in Japan and Australia, but most people generally go with the larger RBs if they can find them.

Common Problems & Reliability

Like the rest of the RB series, the RB20DET is known to be able to take some serious mileage. They can easily break the 100,000-mile (160,000 km) barrier with proper maintenance and care, and it’s not entirely uncommon for 200,000-mile (320,000 km) examples to appear.

The main thing to keep in mind on the RB20 series is going to be timely and proper maintenance. As we’ll get into, the RB series all have documented oiling issues. Making sure proper oil changes are done every 3-5,000 miles is incredibly important.

The timing belt is also known to be a weakness on the RB engines, and should be changed every 60,000 miles at the most. The RB20 is an interference motor, so a broken timing belt can have serious – and expensive – repercussions. On interference engines, when the timing belt breaks the valves do not fully close, which means the piston will run into the valve as it hits top dead center, which will bend or break the valve.

Oil Control System Issue and Fix

The issue with oil control on the RB20 is that the oil pump pushes too much oil into the cylinder head in the upper RPM range. This leads to oil pooling on top and not draining back down into the oil pan because the oil return passages are too small.

While it’s not super common on street driven cars, on the track this can lead to serious oil starvation issues. Oil ends up coming out of the cam breathers and into the inlet system, taking it away from the rotating assembly which needs it.

To fix the RB20 oil control problems it takes five steps. First, you want to block off the rear oil feed gallery to prevent excess oil flowing into the head. Second, you want to add a restrictor to the open oil gallery to control the oil flow to the head better. Third, you’ll want to run an external oil line from the head to the sump for better drainage from the head. This Head Oil Drain Kit from Franklin Performance is made for the RB series.

Fourth, you’ll want to machine out the oil return galleries by 1mm for better drainage. Finally, you’ll want to machine around the galleries so they can take in the oil better (and thus drain it quicker). Additionally, after you have taken these steps, you can also run a larger sump and oil pump to increase oiling. For very high horsepower builds, a dry sump is the ultimate solution.

Here is an excellent guide with a more detailed step-by-step process to solve the problem. The guide also covers the below issue with the crank collar.

Crank Collar Issue and Fix

The problem with the RB20DET crank collar is because the part of the crank’s snout that touches the oil pump drive is too small and wears easily. Both the crank and the pump can become damaged, resulting in the oil pump gear cracking and breaking and a complete loss of oil pressure. The issue is exacerbated by repeated high RPM engagement, and as you can imagine, no oil pressure at high RPM means big problems. This is probably the most common issue on the RB20.

To fix the problem the stock crank collar needs to be machined off and a larger replacement put on that allows for more engagement of the inner oil pump gear. Here is an RB20 crank collar from Franklin Performance.

Apart from these two main issues, as long as adequate maintenance is kept up on the RB20 series will run for lots of miles.

Performance and Mods

Stock, the RB20DET comes with 180-215 horsepower, depending on the year and model. It is very capable of upgrades and is one of the most modded Nissan motors out there. For most people in the US, their RB20DET is likely going to be swapped into an S12/13/14. In that case, you’ll definitely want to make sure you add some horsepower before putting it in. It doesn’t take a ton to make 300 horsepower in the RB20DET, and we’ll show you how below.

RB20DET Mods for 300-450 Horsepower

• Front Mounted Intercooler
• Full 3” Turbo-back Exhaust
• GTR Fuel Injectors (440 cc)
• GTR Fuel Pump (or Walbro 255/Bosh 044)
• GTR Fuel Lines (or aftermarket)
• ECU Tuning
• Turbo Swap

The first thing you’ll want to do is upgrade the stock side mount to a bigger front-mounted intercooler and get a full 3” exhaust. Getting a larger intercooler will allow you to run more boost than stock, and will also drastically improve cooling. A full 3” exhaust, with a high-flow cat or catless dump pipe/J pipe, is needed for reduced back pressure. An intake is optional at this stage, but will add 5-10 horsepower if it’s truly free-flowing.

After you’ve made these mods, you’ll want to look at upgrading the fueling. If you have access to GTR (RB26DETT) parts, those make easy swaps. If not, you’ll want parts that have similar performance. You’ll want 370-440cc injectors, an upgrade over the 270cc stockers, as well as a bigger fuel pump and fuel lines.

The next steps will be ECU tuning and a turbo upgrade. The stock turbo runs out of power at around 275 horsepower and 12 PSI, so you’ll need something bigger for 300+ horsepower. Some of the most popular RB20DET turbo upgrades are the RB25DET stock turbo, RB26DETT T3/T28 stock turbos, VG30DET stock turbo, HKS 2530/2835 turbos, GCG high-flow turbo, Hx35 turbo, GT30R turbo, GT3037/S turbo, and Greddy TD06 turbo. All of these will put you between 300-450 horsepower, depending on other upgrades and supporting mods.

Nissan RB20DET Legacy

Overall, the Nissan RB20DET engine is one of their finest creations of the ‘80s-’90s. While they might not be as heralded as the larger RB25/26, they are still fantastic motors. Stock, they provide adequate performance with exceptional reliability, and when modded they can provide some serious thrills. You can use the provided mod guide to turn your 180-215 horsepower run-of-the-mill RB20DET into a full-fledged 300-450 horsepower beast.

Let us know about your RB20DET experience in the comments below! Also read some of our other RB engine and GT-R guides including a complete RB30 engine guide, VR38DETT engine problems, and 2JZ vs RB26.