Apexi Noir Exhaust Flow Characteristics And Sound Analysis

Hey there, fellow car enthusiasts! Stumbling upon this article likely means you're experiencing some quirks with your Apexi Noir exhaust system, or perhaps you're just researching before making the leap. Either way, you've come to the right place. The Apexi Noir is known for its great blend of performance and sound, but like any aftermarket exhaust, it can sometimes present challenges. Let's dive into common flow characteristics, sound issues, and how to troubleshoot them.

Understanding the Apexi Noir's Flow Characteristics

The Apexi Noir exhaust is designed to improve exhaust flow, leading to increased horsepower and torque. It typically achieves this through larger diameter piping and a less restrictive muffler design compared to your factory exhaust. However, this change can sometimes lead to unexpected consequences.

Potential Problems & Solutions:

• Problem: Loss of Low-End Torque. A common complaint after installing a less restrictive exhaust is a perceived loss of low-end torque. This happens because the engine relies on some backpressure to effectively scavenge exhaust gases at lower RPMs. A too-free-flowing exhaust can actually reduce exhaust velocity at lower RPMs, hindering this scavenging process.

  Solution: This is often a characteristic of the design, but you can sometimes mitigate it.

  • ECU Tuning: The best solution is a proper ECU tune. A tuner can adjust the engine's fuel and ignition maps to optimize performance with the new exhaust. Expect to pay between $300 - $800 for a custom tune.
  • Mid-Pipe Resonator: Adding a small resonator to the mid-pipe can introduce a small amount of backpressure without significantly restricting overall flow. Resonators typically cost between $50-$150 for the part, plus installation.
  • Exhaust Cutout (Advanced): A more aggressive (and expensive) solution is an exhaust cutout. This allows you to bypass the muffler entirely for maximum flow at high RPMs, while retaining the standard exhaust for low-end torque. These can run from $150-$500+ depending on whether they are manual or electronic. Installation will be an additional cost.

• Problem: Exhaust Leaks. Any time you modify your exhaust system, the chance of leaks increases. Leaks disrupt the carefully engineered flow and can cause a multitude of issues.

  Solution:

  • Inspection: Thoroughly inspect all connections (flanges, slip joints) for signs of leaks – soot, discoloration, or even the sound of escaping gas.
  • Tightening: Make sure all bolts and clamps are tightened to the manufacturer's specifications. Use a torque wrench!
  • Gaskets: Replace any questionable gaskets. Exhaust gaskets are cheap and crucial for a proper seal. OEM or high-quality aftermarket gaskets are recommended. Budget $10-$50 per gasket.
  • Exhaust Paste/Sealant: Use a high-temperature exhaust sealant (like Permatex Ultra Copper) on slip joints to create a leak-proof seal. Apply a thin layer before assembling the joint. A tube costs about $10.
  • Welding: If you find cracks or pinholes in the exhaust piping itself, welding is often the best solution. This is best left to a professional welder (expect to pay $50-$150 depending on the complexity).

  Tools Needed: Socket set, wrench set (including a torque wrench), jack stands, inspection light, exhaust sealant, replacement gaskets.

• Problem: Catalytic Converter Issues (Related to Flow). While the Apexi Noir typically bolts to the existing catalytic converter (unless you've also modified that), increased exhaust flow can sometimes accelerate the deterioration of an older or weaker catalytic converter.

  Solution:

  • Inspection: Monitor your car for symptoms of a failing catalytic converter: reduced fuel economy, a rotten egg smell, check engine light (specifically codes P0420-P0430).
  • Replacement: If the catalytic converter is failing, replacement is necessary. High-flow catalytic converters are available, but ensure they are legal in your area (emissions regulations vary widely). Replacing a catalytic converter can cost between $200-$1000+, including labor.
  • O2 Sensor Spacers (Use with Caution): In some cases, an O2 sensor spacer can trick the ECU into thinking the catalytic converter is functioning properly, but this is generally not recommended as it masks the underlying problem and may not be legal.

Analyzing and Addressing Sound Characteristics

The Apexi Noir is designed to offer a sporty and aggressive sound. However, sound is subjective, and sometimes the sound characteristics don't align with expectations or develop unwanted noises over time.

Potential Problems & Solutions:

• Problem: Excessive Drone. Drone is that low-frequency humming sound that resonates within the cabin, especially at cruising speeds. It's a common complaint with aftermarket exhausts.

  Solution:

  • Resonator: As mentioned earlier, adding a resonator to the exhaust system can help to reduce drone.
  • Helmholtz Resonator: A Helmholtz resonator is a specifically tuned chamber designed to cancel out a particular frequency (the drone frequency). This is a more advanced solution, requiring careful calculation and fabrication.
  • Sound Dampening: Adding sound dampening material to the interior of the car (floor, trunk, firewall) can help to absorb the drone. This is a labor-intensive process but can significantly improve the overall cabin noise level.

• Problem: Rattling or Buzzing Noises. These noises are often caused by loose components, vibrating heat shields, or exhaust components contacting the chassis.

  Solution:

  • Inspection: Carefully inspect the entire exhaust system, looking for loose heat shields, loose bolts, or points where the exhaust is touching the frame or suspension components.
  • Heat Shield Repair/Removal: Tighten or replace any loose heat shields. If they are severely damaged, you may be able to remove them entirely (ensure this won't cause heat-related issues with nearby components).
  • Exhaust Hangers: Make sure all exhaust hangers are in good condition and properly supporting the exhaust system. Replace any worn or broken hangers. Polyurethane exhaust hangers can offer improved stability. Hangers are relatively inexpensive, costing between $5-$20 each.
  • Clearance: Ensure there is sufficient clearance between the exhaust system and the chassis. If necessary, slightly adjust the exhaust hangers to create more space.

  Tools Needed: Socket set, wrench set, jack stands, inspection light, pry bar (for adjusting exhaust position).

• Problem: Exhaust "Pop" or "Backfire" on Deceleration. This is often caused by unburnt fuel igniting in the exhaust system. While some people enjoy this sound, it can indicate an issue.

  Solution:

  • Vacuum Leaks: Check for vacuum leaks in the intake system. Vacuum leaks can cause the engine to run lean, leading to unburnt fuel in the exhaust.
  • Exhaust Leaks (Again!): An exhaust leak can introduce oxygen into the exhaust stream, which can ignite unburnt fuel.
  • ECU Tuning: A proper ECU tune can often eliminate or reduce exhaust pops by optimizing the air/fuel ratio during deceleration.
  • AIS/SAS System (If Equipped): Some vehicles have an Air Injection System (AIS) or Secondary Air System (SAS) that injects air into the exhaust manifold to burn off excess hydrocarbons. If this system is malfunctioning, it can cause excessive popping.

General Tips for Maintaining Your Apexi Noir Exhaust

Here are a few general tips to keep your Apexi Noir exhaust system performing optimally and sounding its best:

• Regular Inspections: Periodically inspect the exhaust system for leaks, damage, and loose components.
• Proper Installation: Ensure the exhaust system is installed correctly, with all bolts and clamps tightened to the manufacturer's specifications.
• Quality Components: Use high-quality replacement parts (gaskets, hangers, etc.) when needed.
• Keep it Clean: While not strictly necessary, cleaning your exhaust system periodically can help prevent corrosion and maintain its appearance. Use a mild soap and water solution.

Modifying your exhaust system is a rewarding experience, but it's important to be aware of the potential challenges and how to address them. By understanding the flow characteristics, sound characteristics, and potential issues associated with your Apexi Noir exhaust, you can keep it performing and sounding its best for years to come. Remember, when in doubt, consult with a qualified mechanic or tuner. Good luck, and happy motoring!