The Nissan Skyline R34 GT-R is not just a car; it is an icon of Japanese engineering and a symbol of the ultimate performance coupe. Its RB26DETT engine, originally rated at 280 horsepower under the Japanese gentleman's agreement, has proven to be a monstrously over-engineered platform capable of handling far more power. For serious enthusiasts, the quest often leads to the 700-horsepower milestone—a figure that transforms the GT-R from a quick street car into a true supercar slayer. The most direct and effective path to this goal is a well-planned turbocharger upgrade. However, simply bolting on larger turbos is a recipe for disappointment. Achieving a reliable 700 hp requires a systematic approach, a deep understanding of forced induction, and the willingness to upgrade supporting systems.

Reaching 700 whp (wheel horsepower) on the R34 GT-R’s RB26 is a proven and repeatable goal, but it demands precision. The stock ceramic-turbine twin turbochargers are the primary bottleneck. They are small, heat-sensitive, and simply cannot flow the volume of air needed for this power level. Swapping them out for larger, higher-flowing aftermarket units is the cornerstone of the build. But this upgrade is only as strong as the components that support it—fueling, cooling, engine management, and even the drivetrain must be addressed. This guide provides a comprehensive walkthrough of selecting the right turbochargers, performing the installation, and tuning the system to safely and consistently deliver 700 hp.

The Fundamentals of Turbocharging for the RB26

Before diving into component selection, it is critical to understand how turbocharging works in the context of the R34’s inline-six. The RB26DETT is a 2.6-liter engine that came from the factory with a parallel twin-turbo setup. Each turbo feeds three cylinders, which allows for quicker spool and a broader power band compared to a single large turbo. At 700 hp, you are moving far outside the factory design envelope. The turbos must be capable of supplying approximately 40–45 psi of manifold absolute pressure (MAP) at high RPM, which requires a compressor map that delivers high airflow (around 60–70 lb/min) while staying within the turbo’s efficiency island.

Key concepts to understand include turbo lag (the delay between pedal input and boost onset), boost threshold (the RPM at which the turbo starts producing positive pressure), and backpressure (exhaust restriction that hinders scavenging). For a street-driven 700 hp build, you want turbos that spool reasonably quickly (full boost by 4000–4500 RPM) while still flowing enough top-end air. Going too large—such as a pair of 30R or 35R frame turbos—may push the power band so high that the car becomes annoying to drive on the road. Conversely, turbos that are too small will choke at high RPM and generate excessive heat, potentially leading to detonation.

Selecting the Right Aftermarket Turbochargers

The market for R34 GT-R turbo upgrades is mature, with options spanning from bolt-on hybrid GT-Spec units to full single-turbo conversions. For the 700 hp target, a twin-turbo setup using aftermarket units in the 700–800 hp range is the most practical and cost-effective route. Single turbo conversions can produce the same power (often with even higher peak numbers), but typically sacrifice low-end response and require more custom fabrication, including a new exhaust manifold, downpipe, and intercooler piping.

Turbo Frame Sizes and A/R Ratios

The most common turbo frame sizes for a 700 hp RB26 twin setup are the GTX2871R (often used for up to 600 hp) or the GTX3071R, and the slightly larger GTX3076R. For the 700 hp target, the GTX3071R or GTX3076R with a 0.64 or 0.82 A/R turbine housing is a proven choice. The larger 0.82 A/R housing helps move the power band higher while still maintaining reasonable spool. Some builders prefer the HKS GT-SS or Garrett G-Series G25-660 if they prioritize quick response and are running E85 (ethanol) to lower exhaust gas temperatures. Always check the compressor map: you want the 700 hp airflow point to be inside the 70–75% efficiency island.

Ball Bearing vs. Journal Bearing

For a street-driven car, ball bearing turbos are highly recommended. They offer faster spool, lower friction, and better transient response compared to journal bearing units. Brands like Garrett, BorgWarner, and Precision Turbo offer ball bearing options that are direct-fit or near-direct-fit for the RB26. Although they are more expensive, the improved drivability on the street is well worth the premium.

Reliable Brands and Kits

Reputable manufacturers include Garrett Motion (especially their GTX and G-Series lines), BorgWarner AirWerks (EFR series), HKS, GReddy, and Trust. Complete turbo upgrade kits are available from companies like Nismo, ETS (Extreme Turbo Systems), and Full-Race Motorsports. A well-designed kit includes oil and coolant lines, gaskets, and hardware, saving you the headache of piecing together components. Avoid generic “eBay” turbos—their internal quality, balance, and warranty support are poor, and failure at 700 hp could destroy the engine.

For further reading on turbo specifications, check Garrett’s official performance catalog or HKS’s turbo lineup page.

Supporting Modifications: The 700 hp Foundation

No turbo upgrade can function properly without a robust supporting system. The RB26 engine is strong, but the stock fuel system, intercooler, and engine management are insufficient for 700 hp. Below is a comprehensive list of the mandatory upgrades.

Fuel System Overhaul

At 700 hp, the RB26 will require roughly 45–50% more fuel than stock. The stock fuel pump (even the Nismo version) will be overwhelmed. Install a high-flow in-tank fuel pump such as the Walbro 525 or AEM 340. It is also wise to run a surge tank and a second external pump (e.g., Bosch 044) to prevent fuel starvation under hard cornering and high boost. Upgrade the fuel injectors to at least 1000cc (1000cc/min) or 1200cc secondary injectors (the RB26 uses a 6 injector setup stock; you will likely upgrade to 6 larger injectors or retain the stock pair as auxiliary). For a return-style fuel system, run -8AN feed and -6AN return lines. The fuel pressure regulator must be adjustable (e.g., Aeromotive or Fuelab).

Intercooler and Intake Plumbing

Heat is the enemy of high-boost engines. The factory side-mount intercoolers are inadequate. A large front-mount intercooler (FMIC) with a core size of at least 24x12x3.5 inches is needed. Companies like ETS, HKS, or Mishimoto offer direct-fit kits for the R34. Mandrel-bent aluminum piping with smooth transitions reduces pressure drop. Additionally, a cold air intake or a filtered inlet pipe for each turbo ensures clean air. Consider using a twin-entry intake manifold if you are converting to a single turbo, but most twin-turbo setups can retain the stock intake plenum with a larger throttle body (90mm or larger).

Engine Internals: Do You Need to Build the Bottom End?

The stock RB26 bottom end (forged steel crankshaft, forged rods) is capable of handling 700 hp on a good tune, but it is near its limit. The stock pistons are cast and can crack under detonation. For a reliable 700 hp build, forged pistons (e.g., CP-Carrillo, JE, or Wiseco) are highly recommended. Also upgrade the connecting rods to forged units (e.g., Carillo, Eagle, or Manley). The stock rod bolts are a weak point—replace them with ARP 2000 or L19 bolts. The cylinder head should be refreshed with upgraded valve springs and retainers to prevent valve float at higher RPM. A set of HKS 264° camshafts (272° if you want a more aggressive top end) is a worthwhile addition to help the engine breathe at high boost.

Exhaust System

A free-flowing exhaust is critical. The stock downpipes and catalytic converters are restrictive. Install a 3-inch downpipe (decatted or high-flow cat) and a 3.5-inch or 4-inch cat-back exhaust. A dump pipe (wastegate dump) or a screamer pipe can relieve pressure before the turbine, but be aware of noise limitations. For a twin-turbo setup, use separate downpipes that merge to a single Y-pipe or maintain dual exhausts.

Engine Management and Boost Control

The factory ECU cannot handle 700 hp. You need a standalone engine management system such as Haltech Elite 1500 or 2500, Link G4+ Fury, Motec M150, or ECUMaster EMU Black. These allow full control over fuel, ignition timing, boost (using a 3-port boost solenoid), and auxiliary outputs. A professional tune on a dyno is essential. For boost control, a Turbosmart E-Boost 2 or HKS EVC-S electronic boost controller is highly recommended to stabilize boost and prevent overboost.

Step-by-Step Installation Process

This section provides a high-level installation guide. Actual work requires mechanical competence; if you are not experienced with turbo systems, enlist a professional shop. Always reference a factory service manual for torque specs and procedures.

1. Preparation and Safety

Park the vehicle on a level surface. Disconnect the battery negative terminal. Drain the engine oil and coolant. Work in a well-ventilated area and use jack stands if lifting the car. Gather all parts and tools: a comprehensive socket set (metric), torque wrench, Allen keys, pliers, screwdrivers, a gasket scraper, and a lift for easier access. Have new oil and coolant ready for refill.

2. Removing the Stock Turbochargers

Begin by removing the engine undercover and the OEM air intake system. Disconnect the intercooler piping. The stock turbos are mounted to the exhaust manifold. Unbolt the downpipes from the turbine outlet. Remove the oil and coolant lines. Note: The oil drain lines are especially prone to cracking—replace them with new ones. Unbolt the exhaust manifold from the cylinder head (10mm bolts). Carefully lift the entire manifold-turbo assembly out of the engine bay. It is heavy, so use a helper or support jack. Separate the turbos from the manifolds on the bench. Replace all gaskets with new OEM or aftermarket copper gaskets. Inspect the manifold for cracks—upgrade to a steel or cast iron manifold if needed.

3. Installing the Aftermarket Turbos

Before installing, mock-fit the new turbos on the bench to ensure the oil drain orientation and coolant lines line up. Apply anti-seize to the threads of the turbo-to-manifold bolts. Install the new turbos onto the manifolds with new gaskets and torque to spec (typically 35–45 ft-lbs). Carefully lower the manifold-turbo assembly back onto the engine. Reconnect the downpipes. Attach the oil feed lines (restrictor recommended for ball bearing turbos), oil drain lines (must be downhill with no kinks), and coolant lines. Use new copper washers for banjo fittings. Prime the oil system by pouring a small amount of oil into the turbo feed line before starting the engine.

4. Installing Supporting Upgrades

With the turbos in place, install the FMIC and intercooler piping. Mount the upgraded fuel pump and run new fuel lines. If replacing injectors, remove the intake manifold and replace injectors with new o-rings. Reassemble the intake manifold with a new gasket. Install the boost controller, boost solenoid, and map sensor. Route wiring for the standalone ECU. If upgrading cams, perform the camshaft swap now (requires removing the timing chain).

5. Final Checks and Initial Start-Up

Double-check all hose clamps, bolts, and electrical connections. Refill engine oil and coolant. Reconnect the battery. Turn the key to the ON position and let the fuel pump prime (do not crank yet). Crank the engine with the fuel pump fuse pulled to build oil pressure. Reinstall the fuse and start the engine. Let it idle and check for leaks. The engine may run poorly if the ECU is untuned—do not drive it. Immediately begin the dyno tuning process.

Dyno Tuning and Testing

A professional dyno tune is not optional—it is the difference between a reliable 700 hp and a blown engine. Find a tuner experienced with RB26 engines and standalone ECUs. The initial tune should start with low boost (around 15–18 psi) to verify fuel pressure and AFR. Gradually increase boost to the target (typically 28–32 psi for 700 hp on 93 octane; lower if using E85). Monitor knock counts, exhaust gas temperatures (EGT), and oil temperatures. The ignition timing curve must be conservative enough to prevent detonation but advanced enough for power. Expect the final power delivery to be smooth, with boost onset around 3500 RPM and peak power near 7000–7500 RPM.

On the road, test for drivability: part-throttle response, transition from vacuum to boost, and cold start behavior. Use data logging to review long-term reliability. For additional reading on RB26 tuning, refer to Haltech’s RB26 tuning guide or RB Motoring’s build articles.

Common Pitfalls and How to Avoid Them

  • Overlooking injector duty cycle: At 700 hp, injectors should not exceed 85–90% duty cycle. If they do, upgrade to larger injectors.
  • Ignoring oil cooling: The RB26 generates significant heat. Install an oil cooler with at least a 19-row core and a thermostat to maintain oil temperatures below 230°F.
  • Using cheap wastegate springs: A weak wastegate actuator can cause boost creep. Use quality units from Tial, Turbosmart, or HKS.
  • Skipping drivetrain upgrades: The Getrag transmission and transfer case can handle 700 hp with careful driving, but the clutch must be upgraded. Use a twin-plate clutch (e.g., OS Giken, Exedy Hyper Single) and consider upgrading the propeller shaft and differential bushes.

Conclusion: Owning a 700 hp R34 GT-R

Reaching 700 hp in an R34 GT-R is an engineering adventure that rewards careful planning and meticulous execution. The turbocharger upgrade is the centerpiece, but it is the sum of the supporting modifications that determines success. A properly built 700 hp R34 is not only a thrilling street machine capable of embarrassing modern exotics, but also a reliable tool for track days with proper maintenance. Always invest in professional tuning, high-quality parts, and safety equipment. The GT-R’s legacy was built on power and control—and a 700 hp build honors that legacy in the best possible way.

For owners looking to take the next step, consult with a specialist shop like JP Performance or Top Secret Japan to explore custom solutions. The R34 GT-R community is deep with knowledge—use it to your advantage.