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2008-2014 WRX, 2011-2019 STi (sedan), 2008-2015 STi (Wagon),  2005-2009 Legacy GT (MT), 2006-2009 Legacy GT Spec B, 2005-2008 Outback XT (MT), 2009-2013 Forester XT, 2009-2010 2.5GT



Congratulations on your purchase of the COBB Tuning Downpipe. The following instructions will assist you through your installation process. Please read them first BEFORE beginning the install and familiarize yourself with the steps and tools needed. If you feel that you cannot properly perform this installation, we HIGHLY recommend you take the vehicle to a qualified and experienced automotive technician.

Table of Contents

Part List

  • Downpipe
  • O2 sensor bung plug

Tools Needed

  • 14mm socket
  • 12mm socket
  • 10mm Allen-head socket/ wrench
  • Socket wrench (3/8" recommended)
  • 22mm open/boxed socket wrench or O2 sensor removal tool
  • 14mm open/boxed socket wrench
  • 12mm open/boxed socket wrench
  • 10mm open/boxed socket wrench
  • High temperature anti-seize
  • Penetrating lubricant (ex:WD40)
  • Optional: cut-off wheel or tin snips

Removal of Stock Downpipe

      1) Put the car up on jack stands or elevate car on a lift.

      2) Remove the four plastic clips that hold on the engine cover.
      3) (Optional) Remove the intercooler. It is held in place by three 12mm bolts – one on the bracket on the passenger side and two that attach the intercooler to the turbo. Next, remove the two
          10mm bolts that hold the bypass valve to the intercooler. After removing them, loosen the clamp connecting the bypass valve to the intercooler. You can then remove the intercooler. This
          will provide more space when removing and installing the downpipe.

      4) Remove the eight 10mm bolts holding the upper heat shield to the downpipe – remove the upper heatshield. [Note: You may want to save these, because the upper heatshield can be trimmed
          to fit over the  COBB Downpipe. Trimming instructions can be found at the end of this document.] Remove the two 10mm bolts holding the lower part of the heat shield to the factory up-pipe. If
         you have an aftermarket up-pipe, it will likely not have the bracket for the lower part of the heatshield.

      5) (Optional - Apply penetrating lubricant to the nuts and bolts about half an hour prior to completing thisstep.) Remove the two 14mm nuts/bolts and three 14mm nuts that attach the downpipe to
          the turbo.Save these and the bracket that held the shield shield for reuse with the COBB Downpipe.

      6) Remove the two 14mm bolt that holds the downpipe to the transmission. This bolt location is not used with the COBB Downpipe. Remove any of the bolts or heat shielding if they prevent access
          to the bolt.

      7) Remove the 14mm bolt that holds the downpipe to the bracket hanging off of the transmission. Save this for reuse with the COBB Downpipe.

      8) Remove the nuts, bolts, and springs connecting the stock downpipe to your cat-back. Remember their orientation and save these for reuse with the COBB downpipe.

      9) Disconnect the O2 sensor from the wiring harness at the connector that is attached to the transmission or the transmission crossmember.

      10) The downpipe is loose and can be removed from the car. If there are any other bolts or brackets holding the downpipe to the car, remove them as well. The two sections can be removed as
            one piece. 

      11) Remove the O2 sensor using a 22mm wrench or socket. Save these for reuse with the COBB Downpipe.

Installation of the COBB Tuning Downpipe

*Note: The COBB Downpipe replaces both of the catalytic converter sections after the turbo with a one piece unit.

       1) Install the factory O2 sensor in the rear bung of the COBB Downpipe. Use a little anti-seize on the threads, but do not get any on the probe of the sensor.

      2) Make sure that the bung plug on the cast section of the downpipe is in place and tight. It uses a 10mm Allen-head tool and should be torqued to at least 25 ft-lbs of torque.

      3) Remove the rear doughnut gasket form the factory downpipe and install it in the same position on the COBB Downpipe. A picture is below for identification purposes. Note: Some aftermarket
          cat-backs do not use the factory style doughnut gasket . You will use the gasket that should have been provided with that system. Our cat-back retains use of the stock doughnut gasket.

      4) Place the downpipe into position. It is easiest to slide the cast portion onto the studs first and swing the rear into position, then let the downpipe bracket click into the bracket hanging down
         from the transmission. You may have to swing the cat-back toward the rear of the car so that the downpipe can swing into position. The downpipe should stay in place while you install the
         hardware because of the brackets and studs on the turbo.
      5) Reinstall the bolt that holds the downpipe to the bracket hanging down from the transmission. Leave itloose so that you can install the rest of the hardwareReinstall the bolt that holds the
          downpipe to the bracket hanging down from the transmission. Leave it loose so that you can install the rest of the hardware.

      6) Reinstall the spring-loaded hardware that holds the downpipe to the cat-back. The bolts and springs go on the cat-back side and the nuts toward the downpipe. Tighten the nuts to
          approximately 12-13 ft-lbs.

      7) Reinstall the hardware that holds the downpipe to the turbo. Use some anti-seize lubricant on the threads if possible. If you plan on reinstalling the heatshield, make sure to place the
          heatshield bracket into position. It goes on the back of the cast flange on the COBB Downpipe with the “angled down”part of the bracket toward the center of the car. Torque the
          hardware holding the downpipe to the turbo to approximately 26 ft-lbs.

      8) Torque the hardware holding the downpipe bracket to the bracket hanging down from the transmission to approximately 26 ft-lbs of torque.
      9) Reconnect the Oxygen Sensor.  With the new position you'll need to forgo use of the stock wiring harness clips on the underside of the car and use a zip-tie to keep it up and out of the way of any heat sources and moving parts before plugging it in to the connector.
      10) Reinstall the heatshield if you are doing so. Torque the bolts to approximately 12 ft-lbs. Trimming examples are below.

      11) Reinstall the intercooler in reverse order of removal. Make sure the clamps are tight so there are no air leaks.

      12) Enjoy your new COBB Tuning Downpipe!


Subaru Installation InstructionsCOBB Product Install Instructions for Subaru Vehicles 

Main Installation Instruction Repository for Subaru Parts

SUBARU CALIBRATION SUPPORTCalibration Map Notes for Subaru Vehicles

Link to Subaru Map Notes to see what map you should be on given the parts you've added

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