The Nissan GT‑R’s VR38DETT engine is one of the most robust platforms for high‑horsepower builds. For owners seeking a substantial leap beyond the factory twins, the Turbonetics G35‑770 turbocharger kit offers a compelling balance of quick spool and immense top‑end pull. This guide provides a comprehensive, step‑by‑step approach to installing this kit in your home garage, focusing on the critical details that distinguish a successful, reliable build from a frustrating one. This is an advanced procedure requiring mechanical competence and proper diagnostic tools.

Understanding the Turbonetics G35‑770 Upgrade

The G35‑770 is designed specifically for the GT‑R’s 3.8‑liter engine. It utilizes a 35 mm wastegate and a billet compressor wheel to achieve a broad power band. Unlike smaller upgrades, this turbo moves enough air to support over 700 wheel horsepower while maintaining drivability. The compressor map shows peak efficiency in the 20–30 psi range, making it a strong choice for both pump gas and E85 applications. Before purchasing, ensure your engine internals are healthy and your drivetrain can handle the increased torque load.

Required Supporting Modifications

A common mistake is installing larger turbos on an otherwise stock GT‑R. This leads to severe lean conditions and mechanical failure. Before installing the G35‑770s, your car must have an upgraded fuel system, increased intake and exhaust flow, and a robust engine management solution.

Fuel System Essentials

  • High‑Pressure Fuel Pump (HPFP): The stock HPFP cannot maintain pressure at the higher flow rates demanded by the G35‑770. Upgrade to a Radium Engineering or equivalent HPFP.
  • Injectors: 1300 cc or larger injectors are required. Injector Dynamics or Bosch EV14s work well with E85.
  • Flex Fuel: To safely run E85, a flex fuel sensor and controller are necessary. This allows the ECU to adjust timing and fueling based on ethanol content.

Intake and Exhaust Flow

The stock intake piping and Y‑pipe create a bottleneck at higher airflow levels. Turbonetics recommends a 4‑inch intake system. On the exhaust side, a 3‑inch downpipe setup is the minimum requirement. A full 3.5‑inch or 4‑inch exhaust system will further reduce backpressure and improve spool characteristics.

Intercooler Considerations

With increased boost levels, the stock intercooler cores quickly become heat‑soaked. An upgraded stepped intercooler or a dual‑core setup will keep intake air temperatures in check. This is critical for consistent performance and detonation prevention during summer months or track sessions.

Pre‑Installation Preparations

Preparation reduces downtime. Set aside a full weekend for the swap. Gather all tools and consumables beforehand to avoid unnecessary delays.

Essential Tool List

  • Metric socket set (8 mm–19 mm, deep and shallow)
  • Ratcheting wrenches (flex‑head for tight areas)
  • Torque wrench (ft‑lb and in‑lb ranges)
  • V‑band clamp tool and pry bars
  • Coolant vacuum filler
  • Smoke tester or boost leak tester

Consumables and Parts

  • Motul 5W‑40 or 10W‑40 oil (10 liters)
  • Nissan Long Life Coolant or equivalent ethylene‑glycol mix
  • New gaskets for turbo manifolds, downpipes, and oil return lines
  • T‑bolt clamps and silicone couplers (supplied with kit)
  • Antiseize compound for studs and bolts

Step 1: Removing the Factory Twin Turbos

Begin by disconnecting the battery and draining the engine coolant and oil. Removing the air intake boxes, intercooler pipes, and downpipes provides access to the turbos. Label all vacuum lines and electrical connectors as you work.

Unbolt the downpipes from the turbos. The O₂ sensors can be stubborn; apply penetrating oil the night before. Unbolt the oil feed and drain lines. The lower turbo coolant line is the most difficult fastener on the car—a flex‑head wrench is essential here. With all lines disconnected, remove the water‑to‑oil heat exchanger if necessary to gain clearance. Lift the stock turbos out carefully to avoid damaging coolant lines or wiring.

Inspect the exhaust manifold studs for damage. Replace any that are bent or corroded. Clean the manifold mounting surfaces thoroughly to ensure a proper seal with the new gaskets.

Step 2: Installing the G35‑770 Turbochargers

Installation is the reverse of removal, with specific attention to line routing and torque values. Using a torque wrench on all turbo and manifold hardware prevents warping or snapping studs during thermal cycling.

Oil Return Line Configuration

The G35‑770s feature a -10AN oil drain fitting. Gravity draining is crucial. Ensure the drain line drops smoothly from the turbo to the oil pan without any dips or kinks. A flat or sagging return line will create a blockage, forcing oil past the turbo seals. Use the supplied silicone hose and T‑bolt clamps, and verify the line does not contact the chassis or downpipe when the engine rocks on its mounts.

Coolant Line Routing

Use the supplied silicone coolant hoses and bleed the system thoroughly to prevent air pockets. A vacuum filler is the best tool for this job. If you reuse the stock hard lines, replace the o‑rings at the connection points. Torque all banjo bolts to 20 ft‑lb using new copper washers.

Wastegate Setup and Boost Control

Set the wastegate spring preload according to Turbonetics spec (typically 1–2 turns). Connect the boost reference line from the compressor cover to the wastegate actuator. For higher boost levels, install a boost controller. Verify the wastegate arm moves freely before installing the downpipes.

Intake and Charge Pipe Connections

Slide the silicone couplers onto the turbo outlet and secure them with T‑bolt clamps. Use a light coating of soapy water on the beads to help the clamps seat evenly. Torque the clamps to 40 in‑lb to prevent blow‑off under high boost pressure. Check all intercooler pipe connections for tightness.

Step 3: Post‑Installation Checks and Start‑Up

Before connecting the battery, double‑check all fasteners. Prime the oil system by pulling the fuel pump fuse and cranking the engine over in 10‑second intervals. Do this five or six times until the oil pressure gauge registers pressure. Reinstall the fuse and crank the engine without starting it for three or four compression cycles to build initial oil pressure.

Perform a boost leak test at 20 psi to verify all couplings are secure. Listen for hissing sounds that indicate leaks at the throttle body, intercooler pipes, or couplers. After confirming no leaks, start the engine and let it idle. Check for oil and coolant leaks immediately. Allow the engine to reach operating temperature, then perform a full thermostat cycle to purge air from the coolant system.

Calibration and Tuning

Do not drive the car on the stock tune. The G35‑770 requires a custom calibration to manage fuel delivery and ignition timing. The increased airflow will cause immediate lean conditions and knock if left unaddressed.

Use either a Cobb Accessport or ECUtek system. A dyno tune is highly recommended to safely dial in the air‑fuel ratios and ensure the engine runs knock‑free across the power band. Most tuners will target 11.5:1 AFR on pump gas and 12.0:1 on E85. Boost levels between 20 and 28 psi are common for street applications, with torque management handled by the ECU to protect the transmission.

Common Pitfalls and Troubleshooting

  • Boost Spikes: Check wastegate preload and boost line routing. A loose actuator arm or incorrect spring pressure can cause uncontrolled boost.
  • Oil Leaks from Turbo: Almost always the drain line orientation. Verify the drain line has a continuous downward slope with no low points.
  • Check Engine Light: Re‑check O₂ sensor connections and downpipe fitment. Ensure the downstream sensors are not contacting the chassis, which can cause false readings.
  • Surge or Flutter: This indicates compressor surge. Adjust the boost controller settings or increase the wastegate spring pressure to keep the turbo in its efficient range.

The NAGTROC community forums are an invaluable resource for shared experiences and specific questions. Many members have documented their own G35‑770 builds and can offer advice on local Turbonetics distributors.

Conclusion

Installing the Turbonetics G35‑770 turbos on your GT‑R is a rewarding project that transforms the vehicle. By respecting the supporting modifications required and paying meticulous attention to line routing and tuning, you will create a blisteringly fast yet reliable machine. Take your time, use quality tools, and trust the process. The result is a GT‑R that pulls with authority from 3,500 rpm to redline, offering a driving experience few other upgrades can match.