Why the RB20DET Deserves a Closer Look

The RB20DET is a 2.0‑liter, turbocharged inline‑six cylinder engine that Nissan produced for the Skyline (R32), Laurel, Cefiro, and other models throughout the late 1980s and early 1990s. Its DOHC, 24‑valve head and iron block make it a rugged starting point for enthusiasts who want more power without stepping up to the larger RB25DET or RB26DETT. While the stock 187‑210 hp (depending on year and trim) is adequate for daily driving, the engine responds exceptionally well to a turbocharger upgrade and proper tuning. This article provides a detailed breakdown of the costs involved in swapping the turbocharger on an RB20DET and tuning it afterward, so you can budget accurately and avoid expensive surprises.

Understanding the RB20DET: Stock Strengths and Weaknesses

The RB20DET shares the same 2.0‑L displacement as the naturally aspirated RB20DE but adds a single T3‑flanged turbocharger (typically a Garrett T25 or T28 on later models) and an intercooler. Factory boost sits around 8‑10 psi. The engine is known for its smooth power delivery and willingness to rev, but the stock turbo runs out of steam around 5,500 rpm, and the fuel system (injectors, pump) is only sized for the stock output. Common weaknesses include the fragile stock head gasket under high boost, the MAF sensor’s sensitivity to blow‑by, and the factory ECU’s conservative timing maps. These are all areas that a turbo swap and retune address.

Why Upgrade the Turbocharger?

Enthusiasts swap the RB20DET’s turbo for several reasons:

  • Higher power potential – A larger or more efficient turbo can push the engine well past 300 hp on stock internals, and beyond 400 hp with forged rods and pistons.
  • Improved response – Modern ball‑bearing turbos spool quicker than the original journal‑bearing T28, reducing lag.
  • Better reliability – Upgrading to a unit with a more robust bearing system and higher thermal tolerance reduces the risk of turbo failure at elevated boost levels.
  • Consistency – Aftermarket turbos are designed to hold boost more steadily, which translates to smoother power delivery during a pull.

Turbocharger Swap: A Step‑by‑Step Look

Performing a turbo swap isn't merely unbolting the old unit and bolting on a new one. The RB20DET requires careful matching of the turbo to the engine's airflow needs, and several supporting components must be addressed simultaneously.

Choosing the Right Turbocharger

Turbo selection depends on your power target and driving style. Common options include:

  • GT28 (Disco Potato) – Excellent spool, good for 250‑300 whp on a stock long block. Ideal for street driving.
  • GT30 / GT3071R – Supports 300‑400 whp with moderate lag. A sweet spot for RB20 builds that retain stock internals.
  • GT35R / GT3582R – 400‑500+ whp, but noticeable lag. Usually paired with upgraded cams and ported heads.
  • Precision 5858 or BorgWarner S200SX – Modern dual‑ball bearing designs that offer quick spool and high flow.

Also consider the turbine housing A/R ratio: a smaller A/R improves spool but can choke top‑end power, while a larger A/R shifts power higher in the rev range.

Compatibility With Existing Components

A new turbo rarely bolts straight onto the RB20DET’s original manifold and plumbing. Evaluate these items:

  • Exhaust manifold – The stock cast iron manifold may not fit the new turbo’s flange (e.g., T3 vs T25). A stainless steel or tubular manifold is often required.
  • Downpipe and dump pipe – The position of the turbo outlet changes, so a custom or application‑specific downpipe is needed.
  • Intercooler and piping – The stock side‑mount intercooler becomes a restriction above ~250 hp. A front‑mount intercooler with larger core and 2.5‑inch piping is recommended.
  • Fuel system – Larger turbo demands more fuel. Minimum upgrades: 550‑700 cc/min injectors and a Walbro 255 LPH fuel pump. Some builds also need an aftermarket fuel pressure regulator.
  • Oil and coolant lines – Many aftermarket turbos require -AN fittings and braided lines. Kits are available for the RB20.

Installation Process: DIY vs Professional

A turbo swap on the RB20DET is an intermediate‑to‑advanced job. Steps include draining fluids, removing the intake piping, unbolting the manifold and turbo, swapping oil drain gaskets, and reconnecting everything with new gaskets. Expect 6‑12 hours for a first‑timer. Common pitfalls include snapped exhaust manifold studs (use penetrating oil and heat), incorrect oil drain angle (causes smoking), and overtightening banjo bolts (can crush the oil feed restrictor).

Professional shops typically charge $90–$150 per hour. A straight swap (no custom fabrication) runs 6‑10 hours. If the shop must fabricate a downpipe, re‑route coolant lines, or machine a flange adapter, labor can double.

Labor Cost Breakdown for Turbo Swap

  • Basic bolt‑on swap (using a direct‑fit turbo kit): $500 – $900
  • Swap requiring custom fabrication (new manifold, downpipe, lines): $1,000 – $2,000
  • Additional metal work (altering intercooler piping, moving wastegate actuator): $200 – $600 extra

Supporting Parts: The Hidden Costs

Many first‑time builders overlook the supporting parts. Here’s what a comprehensive turbo swap might require beyond the turbo itself:

  • Turbocharger unit: $800 – $2,500 (Garrett, Precision, BorgWarner)
  • Exhaust manifold: $200 – $800 (tubular stainless, divided or undivided)
  • Downpipe / dump pipe: $150 – $500 (custom or kit)
  • Front‑mount intercooler kit: $300 – $700 (2.5‑inch piping, core size 600x300x76mm typical)
  • Fuel injectors (set of 6): $400 – $800 (injector dynamics, ID1000, or Bosch EV14)
  • Fuel pump: $100 – $200 (Walbro 255 or AEM 340)
  • Oil and coolant line kit: $80 – $200
  • Gaskets, studs, and fasteners: $50 – $150

Total supporting parts cost (excluding labor): $1,080 – $5,350. A budget build might stick to the lower end using used parts and a cheap manifold, but reliability is compromised. A quality build usually lands in the $2,500–$4,000 range for parts alone.

Tuning Costs Breakdown

Once the turbo and supporting mods are installed, the engine will not run correctly without reprogramming the ECU. The stock ECU is designed for the original small turbo and will cause rich or lean conditions, knock, and poor drivability.

Tuning Options for the RB20DET

  • Nistune ECU – A daughterboard that replaces the factory ROM chip. Allows real‑time tuning of the stock ECU. Cost: $450–$700 for the board plus installation. Tuning time: 2‑4 hours.
  • Standalone ECU – Haltech Elite, Link G4+, Motec M130. Cost: $1,100–$3,000. Gives full control over fueling, ignition, boost control, and auxiliary systems.
  • Piggyback systems (e.g., SAFC, eManage) – Less common today because they only adjust a limited number of parameters. Cost: $200–$500, but tuning complexity and results are mediocre.

Dyno Tuning vs Street Tuning

Professional dyno tuning is strongly recommended after a turbo upgrade. A chassis dynamometer provides accurate load readings and safe tuning under controlled conditions. Many shops offer a “dyno tune session” that includes up to six pulls and final adjustments.

  • Dyno time only: $300 – $500 (2‑3 hours)
  • Complete dyno tune with ECU programming: $500 – $1,200 (includes base map, WOT tuning, cruise trimming, and final test)
  • Remote tune (mail‑order base map + self‑fine tune with wideband): $200 – $400 – less reliable for high‑boost setups.
  • Wideband O2 sensor/gauge: $150 – $300 (needed for datalogging)
  • Boost controller: $100 – $400 (optional, but recommended for consistent boost levels)
  • MAP sensor upgrade: $80 – $150 (if running >15 psi, the stock 2‑bar MAP is insufficient)

Total Cost Estimate: Turbo Swap + Tuning

Combining all factors, here are realistic price brackets for an RB20DET turbo upgrade from start to finish:

  • Budget build (lightly used GT28, stock injectors, Nistune with street tune): $2,000 – $3,500
  • Mid‑range build (new GT3071R, 550 cc injectors, FMIC, Nistune dyno tune): $4,500 – $7,000
  • High‑end build (new GT3582R, ID1000 injectors, fuel rail, Haltech standalone with dyno tune): $7,000 – $12,000+

These figures do not include the cost of the engine itself, transmission upgrades, or other drivetrain modifications that may become necessary at higher power levels. A stock RB20DET transmission (FS5R30A) is marginal above 350 hp.

Factors That Shift the Costs

Several variables influence final outlay:

  • Region – Shops in metropolitan areas such as Los Angeles or Sydney may charge $150‑$200/hour, while smaller towns can be half that.
  • Used vs new parts – Buying a used turbo from a reputable seller saves 30‑50% but carries risk.
  • Aftermarket vs OEM replacement – Some companies sell “bolt‑on” kits that preserve the OEM manifold and downpipe, reducing labor.
  • Condition of the existing engine – If the RB20 has high miles or oil leaks, repairs add overhead.

Common Mistakes and How to Avoid Them

  • Overboosting without supporting fuel – Leads to lean misfires and destroyed pistons. Always upgrade injectors and fuel pump before raising boost.
  • Using cheap wastegates – An internal wastegate that cannot hold boost causes surging and power inconsistency. Upgrade to an external 38‑45 mm unit if running >400 hp.
  • Neglecting crankcase ventilation – High boost pressurizes the crankcase, leading to oil leaks and seal failure. A catch can and proper PCV modification are essential.
  • Relying on a mail‑order tune for a daily driver – While convenient, street tuning with a laptop and wideband is time‑consuming and risky without a safety net. A dyno session is a better investment.

Final Advice for a Successful RB20DET Upgrade

The RB20DET remains a strong platform for a budget‑conscious performance build, but the costs of a turbo swap and professional tuning add up quickly. Plan your budget with a 20% contingency for unexpected parts or labor. Join a dedicated RB‑series forum (such as SAU) to find build logs and part recommendations. When selecting a turbo, check Garrett’s official specs for compressor maps to match your power target. For local tuning advice, Haltech’s tuning centre locator can point you to a certified shop.

Ultimately, a well‑executed RB20DET turbo upgrade and tune can transform a mundane daily into a thrilling street car. Invest in quality parts and a reputable tuner, and your engine will reward you with many miles of reliable, boosted driving.