What Are Test Pipes for the G35? A Complete Guide For Beginners

Test pipes are aftermarket exhaust components designed to replace the factory catalytic converters on your Infiniti G35. Popular among car enthusiasts, they boost horsepower, enhance exhaust sound, and reduce costs. However, they come with legal risks due to emissions regulations. This guide covers everything you need to know about test pipes, including their functionality, benefits, installation, and legal considerations.

How Test Pipes Work: Simplified for Beginners

The Analogy: From a Straw to a Smoothie Pipe

Imagine drinking a thick milkshake through a narrow straw—it’s slow and frustrating. The factory catalytic converter acts like that narrow straw, restricting exhaust flow. Test pipes replace this "straw" with a wider, smoother pipe, allowing your engine to "breathe" more efficiently.

The Science Behind Reduced Backpressure

Factory catalytic converters use a honeycomb structure to trap harmful emissions, but this design creates backpressure. Test pipes remove the honeycomb, allowing exhaust gases to flow freely and reducing backpressure by 40–60%. This results in improved scavenging effect, faster engine revving, and a noticeable horsepower boost.

Key Takeaway: Test pipes optimize exhaust flow, similar to upgrading your car’s respiratory system.

Technical Specifications for the G35 Test Pipes

Material and Durability

G35 Test pipes are typically made from 304 or 409 stainless steel. 304 stainless steel offers high corrosion resistance, making it ideal for humid climates like Florida or coastal areas. 409 stainless steel is more budget-friendly but prone to rust over time.

Dimensions and Compatibility

Test pipes for the G35 usually have a diameter of 2.5 inches for OEM fitment or 3 inches for aftermarket exhausts (requiring adapters). The length ranges from 18 to 22 inches, depending on the model year. They are compatible with the 2003–2006 G35 (VQ35DE engine) and the 2007–2008 G35 (VQ35HR engine with header adapters).

Oxygen Sensor Integration

Test pipes include pre-welded O2 sensor bungs to accommodate the factory oxygen sensors. However, removing the catalytic converter often triggers a check engine light (P0420 code). To fix this, you can use O2 sensor spacers or ECU tuning software like UpRev.

Benefits of Installing G35 Test Pipes

Horsepower and Torque Gains

Installing G35 test pipes can yield 5–15 wheel horsepower (WHP) gains on stock engines. For example, a 2004 G35 sedan gained 12 WHP after installing Flashark Racing Test Pipes and a cat-back exhaust.

Enhanced Exhaust Sound

Test pipes increase exhaust volume by 10–15 dB compared to stock. They also improve the tone, delivering deeper, raspier notes under acceleration.

Cost Savings

Test pipes are significantly cheaper than OEM catalytic converters, costing $150–$600 versus $1,500+ for OEM parts. They also eliminate the risk of clogged catalytic converters, saving you money in the long run.

Test Pipes vs. High-Flow Catalytic Converters

Performance Comparison

Test pipes offer greater power gains (8–15 WHP) compared to high-flow catalytic converters (3–8 WHP). They produce a more aggressive, race-inspired sound, while high-flow cats are subtler and street-friendly. However, test pipes are illegal in all 50 states, whereas CARB-approved high-flow cats are legal for street use.

Which Should You Choose?

For track use, test pipes are the better choice for maximum power. For street use, high-flow catalytic converters are recommended to stay legal and avoid fines.

Legal Risks and How to Minimize Them

Federal and State Laws

Removing catalytic converters is federally illegal under EPA regulations, with fines up to $4,800. In California, CARB enforcement is strict, with fines exceeding $1,000 and potential smog check failures.

Workarounds for Enthusiasts

To minimize legal risks, consider using quick-swap systems with V-band clamps for easy removal before emissions tests. Installing spark plug non-foulers can trick the ECU into not triggering a check engine light. Alternatively, reserve test pipes for track days only.

G35 Test Pipes Step-by-Step Installation Guide

Tools and Materials

Before starting, gather the following tools:

• Floor jack and jack stands
• 7/8” oxygen sensor socket
• PB Blaster penetrating oil
• Torque wrench (25–30 ft-lbs)

Installation Process

1. Disconnect the Battery: Prevent electrical shorts by disconnecting the negative terminal.
2. Spray Rusty Bolts: Apply PB Blaster to the manifold and mid-pipe bolts. Wait 15 minutes to loosen rusted components.
3. Remove Factory Catalytic Converters:
   • Unbolt the catalytic converter from the exhaust manifold using two bolts.
   • Unbolt it from the mid-pipe using two additional bolts.
4. Install Test Pipes:
   • Attach the test pipe to the manifold first, then connect it to the mid-pipe.
   • Tighten the bolts gradually in a crisscross pattern to ensure even pressure.
5. Reconnect O2 Sensors: Use extensions if the wiring is stretched.

Post-Installation Tips

After installation, clear any ECU error codes with an OBD2 scanner. Test-drive the car to check for exhaust leaks and ensure everything is functioning properly.

Top Test Pipe Brands for the G35

Flashark Racing Test Pipes

Flashark Racing offers high-quality test pipes made from 304 stainless steel. Their precision CNC flanges ensure a leak-free fitment, and the package includes high-quality gaskets and hardware. Priced at $349.99, they are a durable and reliable option.

FAQs About Test Pipes

Q: Will test pipes pass emissions?

A: No. Test pipes are illegal in all 50 states due to EPA regulations.

Q: How much louder are test pipes?

A: Test pipes increase exhaust volume by 10–15 dB. Resonated designs can reduce drone for a more tolerable sound.

Q: Can I install test pipes myself?

A: Yes, but rusty bolts may require cutting tools for removal.

Q: Do test pipes improve fuel economy?

A: Slight gains (1–2 MPG) are possible due to reduced backpressure.

Q: What’s the best brand for durability?

A: Flashark Racing uses 304 stainless steel, making their test pipes a long-term reliable option.

Final Verdict

Test pipes are a powerful upgrade for G35 owners seeking more horsepower and an aggressive exhaust note. However, they’re illegal for street use in most areas. For track enthusiasts or those in lenient regions, they’re a worthwhile investment. Daily drivers should opt for high-flow catalytic converters instead.