Understanding the RB26DETT Engine

The RB26DETT is a 2.6‑liter inline‑six twin‑turbo engine that powered the legendary Nissan Skyline GT‑R (R32, R33, R34). Its cast‑iron block and aluminum cylinder head provide a robust foundation capable of handling 600–1000+ horsepower with proper modifications. The engine features a closed‑deck design, forged steel crankshaft, and factory oil squirters for piston cooling. However, despite its strength, the RB26 has known weaknesses that must be addressed in high‑output turbo builds: the factory oil pump gears are prone to failure at elevated rpm, the stock head studs can stretch under high boost, and the original fuel system is inadequate for large power increases. Understanding these limitations is the first step to building a reliable turbo system.

Choosing the Right Turbocharger

Selecting a turbocharger for the RB26 involves balancing response, peak power, and durability. Key considerations include the engine’s displacement (2.6 L), desired boost range, and intended use (street, track, drag). Three reputable manufacturers—HKS, Greddy (Trust), and SH Turbo—offer proven options specifically engineered for the RB26.

HKS Turbochargers

HKS has been a dominant player in the Japanese performance market for decades. Their turbochargers for the RB26 feature advanced bearing technologies (thrust ball‑bearing or journal bearing depending on model), high‑flow compressor wheels, and durable turbine housings.

  • HKS GT Series (GT2530, GT2835, GT3240): The GT series offers excellent spool characteristics while supporting 400–600 hp. The GT2530 is a popular choice for responsive street builds, while the GT3240 can push beyond 700 hp.
  • HKS T51R: A massive single‑turbo conversion designed for extreme power (800+ hp). The T51R uses a large KAI turbine and a T51 compressor cover, requiring extensive supporting mods like a custom manifold, external wastegate, and upgraded fuel system.
  • HKS T04Z and T04S: Sleeved turbo models that blend hybrid characteristics with reliability, often used in high‑boost street/strip setups.

HKS turbos are known for consistent quality control and availability of rebuild kits. For detailed specifications, visit the official HKS website.

Greddy Turbochargers

Greddy (Trust) produces a wide range of turbochargers tailored to the RB26, often emphasizing mid‑range torque and durability. Many of their units use Garrett‐based internals with proprietary housings.

  • Greddy TD06‑25G and TD06‑20G: The TD06 series is a staple for 500–650 hp builds. The 25G offers slower spool but higher top‑end flow, while the 20G provides quicker response. Both are compatible with T4 flanges.
  • Greddy T88‑34D and T88‑38D: Designed for 800+ hp, the T88 features a large compressor wheel and robust ball‑bearing cartridge. It is often used in conjunction with Greddy’s intake and exhaust manifolds.
  • Greddy T04Z: Hybrid unit that combines a T04Z compressor with a T3/T4 turbine, offering solid response and up to 700 hp.

Greddy provides complete turbo kits (manifold, wastegate, downpipe) for the RB26, simplifying installation. See the Greddy official site for kit options.

SH Turbochargers

SH Turbo has gained popularity among budget‑conscious builders without sacrificing reliability. Their units are typically based on the Garrett GTX or GT28/GT30 compressor maps, using Chinese‐sourced cores but with quality control improvements.

  • SH 2871R: A direct response to the popular Garrett 2871R. This turbo spools very quickly (full boost by 3500 rpm) and supports up to 400 hp—ideal for street RB26s with stock internals.
  • SH GT3076R: A balanced choice for 500–550 hp. The GT3076R provides moderate spool (full boost ~3800 rpm) and excellent top‑end flow. It is often used with external wastegates to control boost creep.
  • SH GT3582R: Capable of 600+ hp, this turbo requires upgraded fuel and oil systems. Its larger frame can lag slightly but rewards with high‑end power.

SH turbos come with a warranty and are available through distributors like SH Turbo’s official store. Many builders report that with proper oil feed/return and tuning, SH units last as long as premium brands.

Critical Supporting Modifications for Reliability

No turbocharger—regardless of brand—can survive in a poorly prepared engine. The following modifications are essential for a reliable RB26 turbo build.

Engine Internals

  • Forged Pistons and Rods: Stock pistons are hypereutectic and can crack above 500 hp. Forged pistons (CP, Wiseco, JE) and forged rods (Carillo, Manley, Oliver) are mandatory for any build exceeding 600 hp. Aim for a compression ratio of 8.5:1 to 9.0:1 for forced induction.
  • Head Studs and Main Studs: Replace the factory head bolts with ARP head studs (11‑mm or 12‑mm conversion) to prevent head lift. ARP main studs improve lower‑end rigidity.
  • Oil Pump Upgrade: The stock RB26 oil pump gears are prone to failure. Install a billet oil pump gear set (e.g., Nitto, Tomei, or HKS) or a full aftermarket oil pump (e.g., JUN, Kiggly). A baffled oil pan (Canton, Moroso, or custom) helps prevent oil starvation during hard cornering or high‑G acceleration.
  • Valvetrain: Stiffer valve springs (OEM or aftermarket) are needed for sustained high rpm to prevent valve float. Consider upgraded retainers and camshafts if exceeding 7500 rpm.

Fuel System

Fuel delivery must keep pace with air flow. For 500–700 hp, use:

  • 1000–1300 cc/min injectors (Bosch, Injector Dynamics, or Nuke Performance)
  • Walbro 450 LPH or AEM 340 LPH fuel pump (in‑tank); wire it with a relay for consistent voltage
  • Aftermarket fuel pressure regulator (Aeromotive, Radium) with return lines (AN‑6 or AN‑8)
  • E85 compatibility: If using ethanol, upgrade to stainless steel fuel lines and Viton seals

Always install a fuel pressure gauge and a wideband oxygen sensor to monitor mixture during tuning.

Oil and Cooling System

  • Oil Cooler: A large oil cooler (Setrab, Earl’s, or a Mocal thermostatic plate) is essential. Mount it in a well‑ventilated spot (e.g., front bumper area). Use AN‑10 lines and a sandwich adapter.
  • Oil Catch Can: Prevents blow‑by oil from recirculating into the intake, which can cause detonation. A well‑baffled catch can (Cusco, Radium) is recommended.
  • Water Cooling: Upgrade to a high‑flow water pump (OEM Nissan or Koyo), a 3‑row aluminum radiator (Mishimoto, Koyo, or PWR), and a 160–180°F thermostat. Electric fans with a proper shroud improve idle cooling.

Intake and Exhaust

  • Intercooler: A front‑mount intercooler (HKS, Greddy, or PRL) with a core size of at least 600x300x100 mm will keep charge temperatures under control. Ensure pipe diameter matches turbo outlet (2.5–3 inches).
  • Intake Manifold: For high‑boost builds (25+ psi), an aftermarket plenum (Greddy, Plazmaman, or Runner) improves airflow distribution and reduces restriction.
  • Exhaust Manifold: T4 twin‑scroll or log‑style manifolds are common. Use a quality unit (Full‑Race, Greddy, or local custom) that won’t crack under heat cycling.
  • Wastegate: An external wastegate (Tial, Turbosmart, or HKS) with 38‑60 mm diameter is necessary to control boost precisely and avoid creep. Vent to atmosphere or recirculate as needed.
  • Blow‑Off Valve: A reliable BOV (HKS SSQV, Greddy Type S, or Turbosmart) prevents compressor surge. For high boost, use a dual‑ported valve.

Tuning and Engine Management

Even the best hardware will fail without proper calibration. Standalone engine management (Link, Haltech, Motec, or AEM) offers full control over fuel, ignition, boost, and safety parameters. Tuning should be performed on a dynamometer by a professional familiar with the RB26. Key tuning targets:

  • Air‑fuel ratio: 11.5–12.0:1 for pump gas, 11.8–12.3:1 for E85
  • Ignition timing: 14–18° BTDC at peak torque, reducing to 12–14° for high boost
  • Boost control: Use a electronic boost controller (Greddy Profec, AEM, or Haltech) to manage spool and prevent overboost
  • Logging: Monitor knock, exhaust gas temperature, oil pressure, and fuel pressure during tuning

Regular Maintenance

  • Change engine oil every 3,000 miles or after track days (use 10W‑40 or 15W‑50 synthetic with high zinc content)
  • Inspect turbo oil feed line for blockages or leaks
  • Check boost leaks every 6 months using a pressure tester
  • Replace spark plugs (iridium, one step colder) every 10,000–15,000 miles
  • Flush coolant system annually and inspect thermostat operation

A detailed maintenance schedule helps catch small issues before they become catastrophic. For a comprehensive build guide, refer to resources like the Skyline Owners Club forum.

Common Pitfalls in RB26 Turbo Builds

  • Turbo Oil Starvation: Inadequate oil supply due to small feed lines (stock is AN‑4, but AN‑3 is common for ball‑bearing turbos) can cause bearing failure. Always use a restrictor (0.040–0.060 inch) for journal‑bearing turbos running more than 80 psi oil pressure.
  • Boost Creep: On high‑flow turbos with small wastegates, boost can rise uncontrollably at higher rpm. Fix with a larger external wastegate (60 mm) and a properly sized dump tube.
  • Heat Soak: In tight engine bays, the RB26 generates immense heat. Wrap turbo manifolds and downpipes with titanium or fiberglass wrap, and consider a turbo blanket. Ensure the hood venting allows hot air to escape.
  • Lean Conditions from Fuel Pressure Drop: Under high boost, fuel pumps may lose voltage. Wire the pump directly to the battery via a relay, and add a secondary pump if exceeding 700 hp.
  • Detonation: Pre‑ignition can crack pistons quickly. Use a knock control interface (e.g., Link Knock Block) and back off timing when knock is detected. Always run the octane that matches your boost level.

Conclusion

Building a reliable RB26 turbo setup demands careful selection of turbocharger brand and model, coupled with extensive supporting modifications. HKS, Greddy, and SH each offer viable options for different budgets and power targets—ranging from responsive street turbos to all‑out race units. The key to longevity lies in addressing the engine’s inherent weaknesses: upgrading oiling, cooling, and fuel systems, reinforcing bottom‑end hardware, and investing in professional tuning. Whether you are building a daily‑driven 500‑hp Skyline or a 1000‑hp track weapon, following these best practices will ensure your RB26 performs consistently and reliably for years. For further reading, explore build threads on R34GT‑R Forum or consult with reputable tuners who specialize in Nissan RB engines.