How to Install G37 Test Pipes Safely

You can install G37 test pipes safely if you have the right tools, proper lifting equipment, and enough experience working under a car. The job is possible for confident DIY owners, but it is not a simple beginner exhaust swap because the upper catalytic converter bolts are hard to reach and often seized from heat cycles.

G37 test pipes replace the factory catalytic converters, so they are intended for off-road or track use only where permitted by law. Before starting, you need to confirm fitment for your G37 model, prepare new gaskets and hardware, handle O2 sensors carefully, and check for exhaust leaks after the install.

This guide walks through how to install G37 test pipes safely, what to prepare before the job, and what problems to watch for during and after installation.

Can You Install G37 Test Pipes Yourself?

Yes, you can install test pipes yourself if you have a decent set of tools, a solid floor jack, and patience.

A Quick Reality Check: While it is a straightforward bolt-on job in theory, the factory bolts connecting the catalytic converters to the exhaust manifolds (headers) are notoriously difficult to reach and frequently seized from heat cycles. If you aren't comfortable working with frozen hardware in tight spaces, you may want to have this modification handled by a professional exhaust shop.

Are G37 Test Pipes Street Legal in the U.S.?

No. Under the U.S. Clean Air Act, it is a federal violation to remove, bypass, or render inoperative any operational catalytic converter on a vehicle driven on public roads. The EPA’s Clean Air Act emissions tampering rules also prohibit manufacturing, selling, or installing aftermarket parts that defeat emissions controls. Because test pipes remove the emissions-controlling elements entirely, they are strictly sold for “off-road or track use only.” Driving with them on public streets can result in fines, and the vehicle may fail visual or tailpipe emissions inspections in jurisdictions that require them, such as California or New York.

Legal Alternatives to Test Pipes

If you want to modify your G37's exhaust system while remaining compliant with environmental regulations, consider these alternatives:

• Emissions-Compliant Replacement Catalytic Converters: Standard OEM-grade replacement units keep your vehicle fully legal and functional if your factory units have failed.

• High-Flow Catalytic Converters (HFCs): These units use a less restrictive internal substrate to improve exhaust flow while still retaining emissions-reduction functionality. Note: Regulations vary by state. CARB-compliant HFCs are required in states following California emissions rules, while other states may allow EPA-certified aftermarket converters. Always confirm local laws before purchasing.

• Cat-Back Exhaust Systems: Replacing everything after the catalytic converters (the Y-pipe, mid-pipe, and mufflers) alters the exhaust note and improves flow without tampering with the vehicle's mandatory emissions control equipment.

Before You Start the Install

Check Your G37 Model and Fitment

Before ordering your parts, double-check your G37’s drivetrain and body style. While many test pipes share a similar design, there can be slight variations in clearance between All-Wheel Drive (AWD/x-models) and Rear-Wheel Drive (RWD) platforms, as well as minor differences between Coupe, Sedan, and Convertible wheelbases.

Choose Resonated or Non-Resonated Test Pipes

You will need to pick between two primary styles of test pipes:

• Non-Resonated: Straight metal tubes. They offer maximum weight savings, but they are prone to producing a pronounced, metallic "rasp" at mid-to-high RPMs.

• Resonated: These feature a small integrated resonator chamber. They slightly dampen the overall volume but help clean up the tone and reduce high-pitched frequencies.

Prepare the Right Parts and Tools

Do not crawl under your car until you have the necessary equipment. Having the right extension or socket can prevent significant installation delays.

How to Install G37 Test Pipes

Step 1: Park the Car Safely

Park your G37 on a flat, level concrete surface. Pull the emergency brake up tightly. If you have an automatic transmission, ensure it is firmly in Park; if it is a manual, leave it in gear. Place wheel chocks behind the rear tires.

Step 2: Disconnect the Battery

Pop the hood and use a 10mm wrench to disconnect the negative (-) battery terminal. This prevents potential electrical shorts while unplugging the oxygen sensors.

Step 3: Lift and Support the Car

Using secure factory jacking points, raise the vehicle. Place your jack stands securely under the factory frame rails.

Safety Warning: Never rely solely on a hydraulic jack to hold the car up while you are underneath it. Always use high-quality jack stands and shake the car gently before crawling under to ensure it is completely stable.

Step 4: Remove the O2 Sensors

Locate the oxygen (O2) sensors plugged into your factory catalytic converters. Unplug the electrical harnesses first so you do not twist or snap the delicate wires. Then, use your specialized O2 sensor socket to carefully unscrew the sensors and set them aside.

Step 5: Loosen the Factory Catalytic Converters

The factory catalytic converters are secured by three bolts on the upper flange (connecting to the headers) and two bolts on the lower flange (connecting to the Y-pipe).

To reach the top bolts, you will typically need to feed your long 2-to-3-foot extension bar down through the engine bay, starting from behind the intake manifolds. Use a swivel joint at the end of the extension to grip the bolt head from above while an assistant helps guide it from underneath the car.

Step 6: Install the Test Pipes

Once the factory converters are out, clean the mating surfaces of the headers and the Y-pipe using a wire brush. Slip your new gaskets onto the studs and maneuver your new test pipes into place.

Pro Tip: Thread all the nuts and bolts by hand first. Do not tighten any single bolt completely at the start; leave them loose enough to allow for adjustment so you can align the entire exhaust properly before final torquing.

Step 7: Reinstall the O2 Sensors

Apply a thin coat of anti-seize lubricant to the threads of your O2 sensors—being careful not to get any on the sensor tip itself. Thread them back into the bungs on your new test pipes by hand, then snug them down with the O2 sensor socket. Reconnect the electrical harnesses.

Step 8: Check for Exhaust Leaks

With everything tightened down to specification, reconnect your battery and lower the car off the jack stands. Start the engine and let it idle. Carefully listen near the side of the car for any ticking or hissing sounds, which indicate a loose flange or misaligned gasket.

Common Problems During Installation

Rusted or Stuck Bolts

Because exhaust systems endure extreme heat cycles and moisture, factory bolts frequently seize. If a bolt will not budge, do not force it immediately or you risk breaking the stud. Spray it thoroughly with penetrating oil and let it soak for 20 to 30 minutes. If it remains stubborn, applying localized heat with a propane torch can help expand the metal to break the rust weld.

Damaged O2 Sensors

O2 sensors are fragile. It is easy to cross-thread them during reinstallation or damage the wiring if you do not unplug them before unscrewing the component. Take your time and ensure they spin in smoothly by hand before using a tool.

Exhaust Leaks at the Flanges

Reusing old, crushed factory gaskets often leads to exhaust leaks. Always use fresh, high-quality multi-layer steel (MLS) or graphite gaskets. If a leak persists, loosen the hardware, adjust the pipe alignment, and retighten the bolts in an alternating pattern.

Poor Fitment Around the Y-Pipe

Inconsistent quality control in certain aftermarket components can result in slightly warped or misaligned flanges. If the pipe does not line up with your Y-pipe, try loosening the Y-pipe brackets further down the exhaust stream to give yourself a few millimeters of extra play during alignment.

Do G37 Test Pipes Need a Tune?

While the vehicle will run without one, an ECU tune (via platforms like EcuTek or UpRev) is recommended after modifying the primary exhaust path. Removing the factory catalytic converters alters the exhaust scavenging and flow dynamics, which can impact the factory air-fuel mapping. A professional tune recalibrates the engine parameters to account for the modified exhaust flow and optimize overall engine performance.

Final Thought

Installing test pipes on a G37 requires a methodical approach, particularly when dealing with the tightly packaged upper header bolts. Prioritizing safety, using the correct tools, and understanding the local regulatory impact are crucial steps before undertaking this modification.

FAQs 

Will G37 test pipes cause a check engine light?

Yes, in many cases. Because the rear O2 sensors no longer read exhaust after a working catalytic converter, catalyst-efficiency codes such as P0420 or P0430 may appear. Do not treat spacers or tuning as emissions-compliance fixes for a street-driven car. 

Are resonated test pipes better for a daily G37?

Generally, yes. Non-resonated test pipes tend to create a harsh drone at highway cruising speeds and a high-pitched metallic note under acceleration. Resonated options provide a more controlled sound profile that is typically more practical for daily driving.

Can G37 test pipes pass emissions?

They will not pass a tailpipe test or a visual inspection, as the required emissions control equipment is completely missing.

Do test pipes make a G37 louder?

Yes, noticeably. Test pipes remove a primary sound-dampening element closest to the engine. If combined with an aftermarket cat-back exhaust system, the overall volume increases significantly.

Are 370Z test pipes the same as G37 test pipes?

Generally, yes. The Nissan 370Z and Infiniti G37 share the same VQ37VHR engine platform, and many aftermarket test pipes are designed to fit both vehicles. However, minor variations in clearance or hanger placement can occasionally occur depending on the specific model year, body style (coupe vs. sedan), and drivetrain layout (RWD vs. AWD).

More reading: Do You Need a Tune After EGR Delete?