Upgrading the downpipes on a Nissan GT-R is one of the most effective modifications for unlocking additional horsepower and improving turbocharger response. The factory downpipes are restrictive due to integrated catalytic converters and narrow piping. Replacing them with AWE Tuning downpipes frees up exhaust flow, reduces backpressure, and allows the twin turbos to spool more quickly. This guide provides a complete, step-by-step installation walkthrough that will help you perform the upgrade safely and correctly in your own garage. Whether you are a seasoned DIYer or a first-time GT-R owner, following these instructions will ensure a successful installation and long-term reliability.

Benefits of Upgrading Downpipes on the GT-R

Before diving into the installation, it is worth understanding exactly what upgraded downpipes deliver. On the VR38DETT engine, the stock downpipes merge the exhaust flow from each turbocharger into the mid-pipe, but they incorporate primary catalytic converters that create significant heat and flow restriction. AWE Tuning downpipes eliminate those bottlenecks with larger-diameter, mandrel-bent tubing and high-flow metallic catalysts (if you choose the catted version) or straight pipes (if you choose the catless version).

  • Increased horsepower and torque – Expect gains of 30–60 whp depending on your tune and other modifications.
  • Faster turbo spool – Reduced backpressure allows the turbos to reach target boost earlier in the RPM range.
  • Weight reduction – AWE downpipes are lighter than the heavy factory assemblies.
  • Improved exhaust note – The GT-R’s V6 gains a deeper, more aggressive tone without becoming obnoxious.
  • Better heat management – Many AWE downpipes feature a ceramic coating or include heat shielding options to keep engine bay temperatures lower.

Tools and Materials Required

Having the right tools on hand before you start makes the job far smoother. Below is a complete list of what you will need, along with a few optional items that can save time when dealing with rusted hardware.

Essential Tools

  • Socket set with deep sockets – 10mm, 12mm, 14mm, 17mm, and 19mm are the most common sizes for the GT-R exhaust system. A deep 12mm is needed for some nuts on the turbo-to-downpipe flange.
  • Torque wrench – A 3/8” or 1/2” drive torque wrench capable of measuring foot-pounds (ft-lb) is critical for tightening fasteners to specification. Never guess torque on turbo flanges or exhaust joints.
  • Ratchet and extension bars – A long 3/8” ratchet plus a 6” and a 12” extension will help you reach bolts in tight spots.
  • Jack and jack stands (or a lift) – The GT-R sits low; you need at least 18 inches of clearance to work under the car. Use two jack stands rated for 3 tons each.
  • Safety goggles and gloves – Protect your eyes from falling debris and your hands from sharp edges and exhaust heat.
  • Penetrating oil – Brands like PB Blaster or Liquid Wrench are essential for loosening rusted or heat-cycled bolts on the flange.
  • New gaskets and locking nuts – While the original gaskets can sometimes be reused, it is best practice to replace the turbo-to-downpipe gaskets and the exhaust flange gaskets. AWE Tuning includes gaskets and hardware, but verify this.
  • O2 sensor socket (22mm) – The oxygen sensors need to be transferred from the stock downpipes to the AWE units. A dedicated O2 sensor socket or a 22mm crow’s foot wrench prevents damage to the sensor.
  • Anti-seize compound – Apply a small amount to O2 sensor threads and exhaust flange bolts to prevent future seizing.

Optional but Helpful Tools

  • Electric impact wrench – Speeds up removal of undertray bolts and exhaust clamps. Use with care on sensitive fasteners.
  • Flex-head ratcheting wrenches – Great for reaching the lower turbo flange nuts.
  • Transmission jack or block of wood – To support the exhaust mid-pipe while disconnected.
  • A second jack stand – For extra stability when working near the center of the vehicle.
  • Clean rags and brake cleaner – To wipe mating surfaces before reassembly.

Pre-Installation Preparation

Preparation is the key to a frustration-free installation. The GT-R is a complex machine, and rushing can lead to stripped threads or damaged components. Follow these steps before you touch a single bolt.

Cool Down the Engine

Work on a cold engine. The exhaust system retains intense heat for hours after driving. Allow the car to sit overnight or at least two hours after a short drive. A cool engine also makes it safer to handle metal components.

Work in a Clean, Well-Ventilated Area

Choose a level, well-lit garage or driveway. Open the garage door before raising the car. Exhaust fumes and penetrating oil vapors can accumulate, so keep the space ventilated.

Disconnect the Battery (Optional)

While not strictly necessary for a downpipe swap, disconnecting the negative battery terminal prevents any accidental short circuits and resets the ECU, which will then re-learn idle and fuel trims after the new downpipes are installed. If you plan to tune the car immediately, leave the battery connected.

Prepare Fasteners and Threads

Apply penetrating oil to all exhaust flange bolts, turbo-to-downpipe nuts, and O2 sensor threads at least 30 minutes before you begin. For severely rusted fasteners, spray them the night before. This simple step can halve the time spent on removal.

Step-by-Step Installation Guide

This installation follows a logical sequence: raising the car, removing the undertray, disconnecting the exhaust, extracting the old downpipes, fitting the new ones, and reassembling. Each step contains specific details for the GT-R platform.

Step 1: Lift and Secure the Vehicle

Position the jack under the front center jack point (the subframe crossmember). Raise the car until the front wheels are about 18 inches off the ground. Place jack stands under the reinforced pinch weld jack points at the front sides. Gently lower the car onto the stands and confirm it is stable — give the car a shake at the fender. For extra safety, chock the rear wheels.

Step 2: Remove the Undertray and Engine Under Cover

The factory undertray is held by numerous 10mm bolts and a few plastic push pins. Remove them all and lower the tray from the front bumper area back toward the oil pan. You may also need to remove a small metal heat shield near the subframe. Set the undertray aside and inspect it for damage; replace it if it is cracked or missing fasteners.

Step 3: Disconnect the Exhaust System Behind the Downpipes

Locate the exhaust mid-pipe connection. On the GT-R, the stock downpipes connect to the main exhaust with a V-band clamp (on newer models) or a flange with bolts. Loosen the clamp or remove the bolts. If the mid-pipe is supported, use a jack stand or wood block to hold its weight once disconnected. This prevents stress on the remaining connections.

Step 4: Unbolt the Stock Downpipes from the Turbos

The most challenging part of the job is accessing the turbo-to-downpipe flange nuts. There are four nuts per turbo, typically 12mm or 14mm. Use a deep socket with a long extension to reach the lower nuts. The upper nut on each flange is difficult to see; feel for it and use a flexible ratcheting wrench if possible. Apply penetrating oil if any nut resists.

Use a six-point socket to avoid rounding. Remove all eight nuts and set them aside. Do not lose the small washers.

Step 5: Remove the Oxygen Sensors

Carefully unscrew the oxygen sensors from the stock downpipes. The front O2 sensors are located before the primary cats, and the rear sensors are after the cats. Use an O2 sensor socket to avoid damaging the sensor body. Note which sensor came from which position (bank 1 and bank 2). Clean the threads with a wire brush and apply anti-seize to the new sensor threads before reinstalling into the AWE downpipes later.

Step 6: Remove the Stock Downpipes

With the exhaust disconnected and the O2 sensors removed, the downpipes should slide out. Work one side at a time. Tilt the downpipe downward and toward the rear of the car to clear the turbo flange and the subframe. It may require some maneuvering — rotating the pipe while pulling helps. If the downpipe seems stuck, check for an O2 sensor wire bracket that is still attached.

Remove it carefully to avoid bending the lines.

Step 7: Install the AWE Tuning Downpipes

Before installing, compare the AWE downpipes to the stock ones to ensure they match. Apply a thin coat of anti-seize to the flange bolts of the new downpipes. Slide each downpipe into position from below. Start with the turbo flange side: align the holes and push the pipe onto the studs. You will need to lift the pipe slightly to get the studs through.

Once both downpipes are in place, hand-thread the flange nuts onto all studs. Do not tighten yet — leave them loose to allow for adjustment.

Next, align the outlet side of the downpipe with the mid-pipe connection. Install the gasket and the clamp or bolts. Tighten the mid-pipe connection slightly but not fully; you will torque everything after all adjustments are made.

Step 8: Reinstall the Oxygen Sensors

Thread the O2 sensors into the bungs on the AWE downpipes. Ensure the sensors are in the correct position (front sensors in the pre-cat bungs, rear in post-cat). Torque to 25–30 ft-lb using an O2 sensor socket. Be careful not to cross-thread. Route the sensor wiring away from moving parts and use zip ties to secure any slack.

Step 9: Torque All Fasteners to Specification

This is a critical step. Refer to the AWE Tuning provided specifications or use these general values:

  • Turbo-to-downpipe nuts: 35–40 ft-lb (check for factory spec of 25 Nm + 90 degrees, but with fresh nuts, 35 ft-lb is safe).
  • Downpipe-to-mid-pipe clamp/bolts: 30–35 ft-lb (do not overtighten V-band clamps).
  • O2 sensors: 25–30 ft-lb.
  • Undertray bolts: hand tight only — use a 1/4” ratchet.

Work in a crisscross pattern on the turbo flanges to ensure even pressure. Re-torque all fasteners after a short heat cycle (see post-installation checks).

Step 10: Reinstall the Undertray and Heat Shields

Place any heat shields back in position. Bolt the undertray back into place using the original fasteners. Ensure the undertray fits flush; any large gaps can cause noise or drag. Once the undertray is secure, double-check that nothing is hanging or rubbing against the downpipes.

Step 11: Lower the Vehicle

Slowly raise the car off the jack stands, remove the stands, and lower it to the ground. Do not start the engine until you have visually inspected all connections one more time.

Post-Installation Checks and Final Torquing

After the car is on the ground, perform these essential checks before and after starting the engine.

Cold Check

  • Verify all nuts and bolts are tight. Wiggle the downpipes by hand — they should not move.
  • Check that O2 sensor wires are not pinched or touching the exhaust.
  • Reconnect the battery if you disconnected it.

Startup and Leak Test

Start the engine and let it idle. Listen for any exhaust leaks — a ticking or hissing sound indicates a leak at a flange. If you hear a leak, shut off the engine immediately, allow it to cool, and re-torque the offending bolt. A small exhaust leak can cause a loss of power and a check engine light.

Use a shop rag or glove to block the tailpipe briefly; this pressurizes the system and makes small leaks audible. Do not hold it for more than a few seconds. If no leaks are present, rev the engine gently to 2000–3000 RPM while listening again.

Drive and Re-Torque

Take the car for a short test drive (5–10 minutes) to bring the exhaust system up to operating temperature. During the drive, make a few partial-throttle pulls to seat the gaskets. Return to your workspace and let the car cool for 10 minutes. Then re-torque all turbo flange nuts and the mid-pipe connection. Heat cycling often loosens fasteners slightly; this step ensures long-term tightness.

Common Issues and Troubleshooting

Even with careful preparation, installation challenges can arise. Here are solutions to the most common problems encountered during GT-R downpipe swaps.

Stubborn Turbo Flange Nuts

The nuts on the turbo studs are notorious for being tight and rusted. If a nut starts to round off, use a high-quality six-point socket. If that fails, use a nut splitter or carefully cut the nut with a cutoff wheel. Replace all nuts with new ones from AWE.

O2 Sensor Cross-Threading

O2 sensor threads are fine and easily damaged. Always start threading by hand for several turns before using a wrench. If the sensor goes in crooked, remove it and realign. A damaged bung can be repaired with a thread chaser, but it is better to avoid the issue.

Check Engine Light (CEL) After Installation

If you installed catted downpipes, a CEL is still possible because the high-flow cats may not convert enough to satisfy the rear O2 sensors. This is normal and can be addressed with a Cobb Accessport or other tuning solution to disable the rear O2 monitors. Catless downpipes will almost certainly trigger a CEL unless the ECU is tuned. Plan accordingly.

Exhaust Drone or Rattle

Ensure the downpipes do not contact the subframe or transmission tunnel. Improper alignment can cause vibration. Loosen the connections, reposition the downpipes, and re-tighten. Also check that heat shields are not touching the downpipes.

Performance Gains and Tuning Considerations

Installing AWE Tuning downpipes is a significant upgrade, but to fully realize the potential, a custom ECU tune is highly recommended. The stock ECU will adapt to the increased airflow to some extent, but you will see an additional 20–30 horsepower and safer air-fuel ratios with a proper tune. Many GT-R owners pair downpipes with a cat-back exhaust, upgraded intercooler, and a Cobb Accessport or Ecutek flash tune.

If you live in an area with emissions testing, be aware that catless downpipes will fail visual and tailpipe inspections. AWE offers catted downpipes that are legal for road use in most states, but check local laws. For maximum track performance, catless downpipes combined with a race tune are the gold standard.

Conclusion

Replacing the factory downpipes with AWE Tuning downpipes is one of the most rewarding modifications you can perform on a Nissan GT-R. Not only does it liberate horsepower and sharpen throttle response, but the installation itself is a satisfying project that any competent DIYer can complete over a weekend with the right tools and preparation. Follow this guide carefully, pay attention to torque specifications, and always re-check connections after a heat cycle. The result will be a more responsive, better-sounding, and faster GT-R that you built yourself.

For additional resources, refer to the official AWE Tuning product page for detailed specifications, join the GT-R forums for community support, and consult a professional tuner if you plan to dial in the ECU afterward. Happy wrenching.