Downpipe Exhaust/Test Pipes for 2008-2013 Infiniti G37 Z34

FAQ

Q1: What exactly are test pipes for the G37?

A1: Test pipes replace the catalytic converters in the exhaust path between the headers and the rest of the exhaust system. On the G37's VQ37VHR engine, the test pipes sit directly after the headers, removing the primary cats that choke exhaust flow. They're called test pipes because they were originally used for dyno testing where you'd remove restrictions to measure true engine output. Now they're a popular upgrade for owners who want maximum flow and sound.

Q2: How much power do test pipes add to the G37 VQ37VHR?

A2: Test pipes alone add minimal peak power—maybe 5-10 wheel horsepower at best. The real benefit is improved response and a broader powerband. The VQ37VHR is a high-revving V6 that makes power up top, and removing the cats lets it breathe more freely. dyno results vary, but expect 8-15whp with a full exhaust (headers + test pipes + axle-back) on a tuned car. Test pipes without other supporting mods are mostly about sound.

Q3: Will test pipes trigger a check engine light on my G37?

A3: Almost certainly, yes. The post-cat O2 sensors on the VQ37VHR will register the absence of a catalyst and throw a P0420 or P0430 code. Some people drive with the CEL on, but it bothers most owners. The fix is either an O2 spacer (bypasses the sensor electrically) or a tune that adjusts the fuel mixture to compensate. Resonated test pipes include a small catalytic converter that helps reduce CEL issues while still improving flow.

Q4: Resonated or straight-through test pipes for the G37?

A4: Resonated test pipes include a small, high-flow cat or resonance chamber that quiets down the exhaust drone and reduces rasp without killing flow. Straight-through test pipes give maximum flow and the loudest, most aggressive sound. Here's my take: if you care about daily drivability, resonated pipes are worth it. The VQ37VHR already has a pretty raw exhaust note, and straight-through test pipes can get fatiguing on long drives. Track-focused builds can go straight-through.

Q5: Are G37 test pipes street legal?

A5: No, not with the cats removed. In California and most states with emissions testing, removing the catalytic converters is illegal for on-road vehicles. California Vehicle Code Section 27156 explicitly prohibits this. Some states have visual-only inspections where you might slip by, but OBD-II states will fail you immediately. Keep the stock cats if you need emissions, or accept that you're driving an off-road-only vehicle.

Q6: Which G37 and 370Z models fit these test pipes?

A6: The VQ37VHR engine found in the 2009-2016 Nissan 370Z, 2008-2013 Infiniti G37 Coupe and Sedan, and 2014-2015 Q60 convertible. The earlier VQ35HR 350Z and G35 use different test pipes—the VQ37VHR has a different exhaust manifold layout. Make sure you're getting the right part for your engine.

Q7: Do test pipes change the exhaust sound on the G37?

A7: Dramatically. The VQ37VHR already sounds good from the factory—Nissan's engineers tuned the exhaust to be sporty. Remove the cats and it gets louder and raspier, especially at higher RPMs. The exhaust note becomes more raw and aggressive. At idle, you notice the difference immediately. Some people love the sound, others find it too harsh. I'd listen to sound clips before committing.

Q8: Can I install G37 test pipes myself?

A8: Installation is more involved than a typical bolt-on. The test pipes attach directly to the headers, which means working in tight space with the engine still in the car. You'll need to disconnect the O2 sensors, remove the existing catalytic converters, and seal everything properly. Expect 2-4 hours if you're experienced, longer if it's your first exhaust job. New gaskets and high-temp sealant are essential—leaks at the header connection cause cabin smells.

Q9: Do test pipes affect fuel economy on the G37?

A9: With a tune or O2 spacer to maintain proper air/fuel ratio, fuel economy stays roughly the same. Without compensation, the engine runs slightly richer, which can reduce MPG slightly. The bigger issue is smell—unburned fuel at low loads makes the exhaust smell richer and oilier. Once the engine management adapts or you add a tune, the smell decreases significantly.

Q10: What's the difference between test pipes and a downpipe for the G37?

A10: On the G37, there's no separate downpipe like on turbo cars. The exhaust manifold connects directly to the catalytic converters, then to the rest of the exhaust. Test pipes replace the cats. If you're looking for maximum flow, headers + test pipes + axle-back exhaust is the complete bolt-on path. There's no downpipe to upgrade separately.

Q11: Should I get resonated or straight test pipes with my aftermarket exhaust?

A11: It depends on the exhaust. If you're running a loud axle-back or cat-back system, resonated test pipes help balance the sound and reduce drone. A quieter aftermarket exhaust can handle straight-through test pipes without becoming unbearable. Think of it as tuning the total system sound, not just one component.

Q12: What other mods pair well with G37 test pipes?

A12: Long-tube headers are the natural companion—they remove the factory manifold restrictions upstream of the test pipes. After that, a cat-back exhaust ties the system together. For power, a tune helps the ECU optimize for the increased airflow. The VQ37VHR responds well to bolt-ons when done in the right order.