The COBB Tuning Bell Mouth downpipe begins with the CAD designed turbo outlet that directs the exhaust exiting the turbo & waste gate into the large 3″ diameter pipe. The design permits the exhaust to flow with very little turbulence to the single high flow catalytic converter resulting in big power gains throughout the entire RPM range. The metal substrate cat is highly efficient, allowing the exhaust to flow much easier than the factory cat 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 or STI.
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 a wide band O2 sensor perfectly. 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 located immediately after the cat to be used by the second OEM O2 sensor. All tubing used in the fabrication of this downpipe is 304 stainless steel for increased corrosion resistance and a beautiful finish. The end of the downpipe tapers down to a flange that uses the stock donut gasket and factory spring bolts to aid in flex, longevity and ensure proper fitment. This provides an improved seal compared to other methods, as well as reduced noise and vibration. An additional benefit is that it makes the COBB 3″ Downpipe compatible with any cat-back exhaust that mates to the factory downpipe.