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 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. 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.
Exhaust gasses are guided through 3-inch diameter tubing into the center inlet of the fully-24-inch wide muffler section. Internal to the muffler, the exhaust gasses pass through a reversed Y merge, efficiently splitting the exhaust into separate muffling chambers on each side of the canister. 2.5-inch outlets emerge symmetrically from each side of the canister and direct the exhaust out the rear through quad polished exhaust tips. This straight-through exhaust design is much more effective at reducing exhaust back-pressure as can be seen in the illustrations.
304 stainless steel is used throughout the exhaust construction. All components are meticulously TIG welded for outstanding appearance and strength. Four custom exhaust tips fill the factory bumper cut-outs perfectly, protruding just enough to show off the COBB logos etched into the top of each polished tip. Perfect fitment is achieved with either the Subaru factory downpipe or the COBB 3" SS Downpipe.
The COBB 3" SS Cat-back Exhaust for the 2008+ Subaru STI is a triumph in design and execution. Install the COBB 3" SS Cat-back Exhaust on your STI and experience performance like no other.