Honestly, if I had a dollar for every time a VQ owner walked into the shop stressing over their exhaust setup, I’d have enough to buy a fresh crate motor. Listen to me: you’re chasing that perfect aggressive tone for your G37 or 370Z, but you’re terrified of your car sounding like an angry trumpet. I get it.
You already know the factory cats are choking your VQ37VHR. You know you need to rip them out. The real headache? Deciding between resonated vs non-resonated setups.
Before we start splitting hairs over acoustic frequencies and dyno sheets, let's cut the fluff. Here is exactly what you need to know.
Quick Takeaways: Which Setup Fits Your Build?
- Choose Non-Resonated if: You are chasing absolute maximum peak wheel horsepower (WHP), you run a high-quality aftermarket catback that already handles frequencies well, you plan on running a flame map (UpRev/EcuTek), or you just want the loudest, rawest track sound possible.
- Choose Resonated if: Your car is a daily driver, you are running the stock catback (or just an axle-back), you have zero tolerance for highway drone at 3,000 RPM, and your main goal is eliminating the infamous VQ metal rasp.
- Performance Delta: The power difference between the two is negligible on street cars (typically within 1-3 whp on a dyno).
- The Check Engine Light: Both styles will likely throw a CEL without O2 spacers or a proper ECU tune.
What Are Test Pipes and Why Upgrade?
Factory catalytic converters are heavy, dense honeycomb bricks designed to keep emissions legal. They are also massive bottlenecks. When you step on the gas, those cats act like a cork in your exhaust system, creating backpressure that kills mid-range torque and dulls throttle response.
By swapping them out for test pipes, you are literally giving the engine room to breathe. But removing that restriction dramatically changes the acoustics of the exhaust gases exiting the block.
Resonated vs Non Resonated Test Pipes: The Core Differences
Let's look at the actual physics of what's happening under your car.
Physical Structure & Flow Dynamics
Non-resonated pipes are essentially straight, hollow steel tubes. From a pure fluid dynamics perspective, they offer the path of least resistance. The exhaust gases exit the headers and smash straight through to the Y-pipe. It’s raw, unrestricted airflow.
A resonated pipe features a slightly wider section containing a perforated core wrapped in packing material (usually fiberglass or stainless steel mesh). The exhaust gas still flows straight through the center hole, but sound waves expand into the packing material.
The Sound Factor (Volume vs. Tone)
If you want volume, non-resonated is your ticket. It is violently loud on cold starts. However, it doesn't filter anything. Every harsh frequency the VQ engine makes is amplified.
Resonated pipes don't necessarily make the car quiet—they just clean up the tone. The resonator targets and absorbs high-frequency sound waves. You lose a bit of the raw volume, but you gain a much deeper, throatier growl.
Deep Dive: G37 and 370z Resonated Test Pipes vs Non-Resonated
The VQ35 and VQ37 platforms are notoriously difficult to make sound "good." If you just bolt straight pipes onto these engines, you get what the community calls the "VQ Trumpet."
Managing the Infamous VQ "Rasp"
Rasp is that high-pitched, tinny, rattling noise that happens when you let off the throttle or hit the upper RPM ranges.
If you are running the stock Y-pipe and muffler, bolting on non-resonated pipes will almost guarantee severe rasp. The stock system isn't tuned to handle the sudden influx of raw acoustic energy. In this scenario, g37 resonated test pipes are a lifesaver. They act as a buffer, smoothing out the exhaust pulses before they hit the rest of your system.
But, if you already have a premium, well-designed 3-inch true dual catback that effectively manages sound, you can absolutely get away with running a set of G37 & 370z non resonated test pipes without sounding like a weedwacker. It gives you the raw mechanical growl without the tin-can vibration.
Dyno Power Gains: Do Resonators Rob Horsepower?
A lot of guys on the forums will tell you resonators kill flow. Let's look at the numbers.
| Setup Type | Est. Wheel Horsepower (WHP) Gain | Backpressure | Best Use Case |
|---|---|---|---|
| OEM Catalytic Converters | Baseline | High | Emissions compliance |
| Resonated Test Pipes | + 7 to 10 whp | Very Low | Daily driving, deep tone |
| Non-Resonated Test Pipes | + 8 to 12 whp | None | Track racing, maximum flow |
On a dyno, non-resonated pipes do make slightly more power at redline. But we are talking about 1 to 3 whp. Unless you are building a dedicated time-attack car where every ounce of weight and fraction of horsepower matters, you aren't going to feel the difference in the driver's seat.
Flashark 2.5" Non-Resonated Test Pipes (2008-2018 G37/370Z)
$175.00 $139.99
- Max Flow: 2.5" T-304 Stainless Steel & CNC Flanges
- Sound: Aggressive, raw VQ tone (Non-Resonated)
- Fitment: 370Z (09-18), G37 Coupe/Sedan/G37x (08-13)
Fitment, Installation, and the "Demon Bolts"
🔧 Mechanic's Notebook: The Dealership Nightmare
I remember back in 2023, a clean manual 370Z came into the shop for a baseline breather build. The owner wanted to swap his cats out in the driveway but gave up and towed it to us. When we got it on the lift, we saw why.
If you are doing this install yourself, pay attention. The three top bolts connecting the factory cats to the exhaust manifolds are affectionately known in the community as the "Demon Bolts." Because they suffer through thousands of heat cycles, they practically weld themselves together with rust. A lot of beginners look at online tutorials, climb under the car, strip the bolt head, and then they are completely stuck. I suggest you never tackle those from the bottom.
⚠️ Expert Installation Tips
- Soak it: Spray PB Blaster or Kroil on those bolts every night for three days before you start the job.
- Top-Down Attack: For the Demon Bolts, go in from the top of the engine bay. Remove the intakes. Use a minimum of three feet of heavy-duty extensions and a swivel socket.
- Leverage: Use a massive breaker bar. Don't use an impact gun right away; you will snap the stud.
Whether you are installing 370z resonated test pipes or going full straight pipe, the pain of the installation is exactly the same. But the second you fire up the engine, that frustration disappears.
Which Should You Choose for Your Build?
Look, there is no universal "best" choice here. It comes down to your tolerance for noise and your end goals.
If you want the absolute most efficient flow, love the raw mechanical sound of a VQ, and plan on shooting flames with an EcuTek tune, going fully non-resonated is the answer. It’s pure, unfiltered performance. Just be prepared for the volume.
If you daily drive your car, share a wall with angry neighbors, and absolutely hate the sound of metal rattling at 4,000 RPM, spend the extra money or rethink your catback pairing.
Frequently Asked Questions (FAQ)
Q1: Will non-resonated test pipes cause a Check Engine Light (CEL)?
A1: Yes, absolutely. Removing the factory catalytic converters removes the substrate that the downstream O2 sensors monitor. You will need O2 sensor spacers (defoulers) or a proper ECU tune to disable the CEL.
Q2: Do resonated test pipes lose power compared to non-resonated?
A2: The difference is extremely marginal. Because resonated pipes still have a straight-through internal design, they flow incredibly well. You might lose 1 to 2 wheel horsepower compared to non-resonated pipes, which is imperceptible on the street.
Q3: How much louder are non-resonated test pipes on a G37?
A3: Expect a volume increase of around 30% to 40% over your current setup. Cold starts will be violently loud, and the exhaust tone will be much more aggressive under wide-open throttle.
Q4: Will test pipes make my 370z shoot flames?
A4: If you are running non-resonated pipes combined with a specific ECU tune (flame map), yes, it is highly likely. We do not recommend trying to shoot flames with resonated pipes, as the raw fuel and heat can blow out the internal packing material.
Q5: What exactly is "rasp" and how do resonated test pipes fix it?
A5: Rasp is a harsh, high-frequency metallic vibration sound, almost like shaking a coffee can full of bolts. Resonators use acoustic cancellation and sound-absorbing packing material to capture and eliminate those specific high frequencies.
Q6: Can I pass emissions or smog with test pipes?
A6: No. Removing your factory catalytic converters makes the vehicle illegal for street use in emissions-controlled areas (like California). Test pipes are strictly for off-road/track use.
Q7: How long does it take to install test pipes on a 370z/G37?
A7: For an experienced mechanic on a lift, it takes about 2 to 3 hours. If you are doing it on jack stands and hit the rusted "Demon Bolts," it can easily turn into an all-day job.
Q8: Do I need an ECU tune after installing test pipes?
A8: While you can drive the car without a tune (ignoring the CEL), we highly recommend it. A tune adjusts your Air/Fuel Ratio (AFR) to compensate for the massive increase in exhaust flow, maximizing your actual horsepower gains.
Q9: What's the difference between test pipes and high-flow cats (HFC)?
A9: High-Flow Cats still contain a metallic honeycomb core (usually 200-cell) to filter out exhaust fumes and keep things somewhat legal, reducing volume. Test pipes are completely hollow tubes with zero filtration.
Q10: Do non-resonated test pipes drone on the highway?
A10: That depends heavily on your catback exhaust. If you pair non-resonated pipes with a muffler-delete axle-back, you will experience severe drone inside the cabin around 3,000 RPM. A quality catback will minimize this.
Q11: Do test pipes smell bad?
A11: Yes. Because there is no catalyst to burn off the unspent hydrocarbons, your exhaust will smell strongly of raw gas, especially when idling at stoplights.
