COBB SS 3" Catted Downpipe

- 2015+ STI

Ships for free in the 48 states

SKU: 524203

Out of Stock

The COBB Tuning turbo downpipe is one of the premier modifications most owners look to upgrade on their vehicle. By opening the diameter of exhaust flow coming out of the turbo, the COBB downpipe unleashes more power potential over the stock restrictive unit.


The COBB Tuning downpipe begins with the CAD designed bellmouth that directs the air coming out of the turbo. The design permits the air to flow with very little turbulence to the single high flow catalytic converter. This metal substrate cat is highly efficient, allowing the exhaust to flow much easier than the factory unit ever would. The COBB downpipe, combined with our Accessport engine management, is one of the most easy installations for any enthusiast looking to unlock the true potential of their WRX.

The engineering that went into the COBB 3" Downpipe started with the CAD designed investment-cast turbine outlet, made of 304 stainless steel for enduring corrosion resistance and reduced heat transfer to the engine bay. The shape of the outlet flange smoothly blends the turbine outlet and wastegate gases. The outlet flange is configured with an O2 sensor bung to accommodate the stock O2 sensor.

A custom spun metal substrate high flow catalytic converter comes next. This one piece 400 grade stainless steel cat has a much higher flow rate and longer lifespan compared to ceramic or "brick" style cats. It also reaches operating temperature faster than other style cats for cleaner cold-start emissions. A second O2 sensor bung is used by the second OEM O2 sensor.

All tubing used in the fabrication of this downpipe is 304 stainless steel for increased corrosion resistance. The end flange uses the stock donut gasket and factory spring bolts to aid in flex, longevity and proper fitment. This provides an improved seal compared to other methods, as well as reduced noise. An additional benefit is that it makes the COBB 3" Downpipe compatible with any cat-back exhaust that mates to the factory cat section.

  • CAD designed cast turbo outlet for maximum flow
  • Minimal bends for less restriction
  • 304 stainless steel throughout for corrosion resistance
  • Custom spun metal substrate high flow cat
  • Two O2 bungs for factory sensors
  • Stock donut gasket for optimal sealing and long life
  • 2 customer reviews

    Average rating
    (based on 2 reviews)
    Ease of Installation
    Fit / Quality
    Overall Satisfaction
    1. Great Product

      By Bradley March 29, 2018

      Take this with your favorite cat-back exhaust and hear that boxer rumble. Definitely my favorite mod that I have put into my STI.

    2. Awesome build quality, fit and finish is amazing!

      By Jay May 23, 2017

      This is the only down pipe I have so I can't compare them to the others out there. In my option, this product is well worth the money. Solid make product, fitment was spot. The high flow cat does allow some of that gas smell through so if you drive in traffic a lot high flow cats or cat less might not be for you. Installation is time consuming as you have to remove the intercooler and a lot of bolts and screws are hard to reach and harder to get leverage on. I was able to complete the install by myself but it toke almost a full 8 hours. I'm not a professional by any means, so if you are you'll probaly have a lot easier time. Hope this review was helpful!

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