Exhaust Question about DP and cat back
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This is a discussion on Exhaust Question about DP and cat back within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; Hello everyone, I'm new to this site and actually just bought my first STI (2004) a couple weeks ago. This ...

  1. #1
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    Exhaust Question about DP and cat back

    Hello everyone, I'm new to this site and actually just bought my first STI (2004) a couple weeks ago. This thing is completely stock except for a Cobb DP that I bought from a friend. The DP hooks directly up to the oem catback. My question is what size is the stock cat back so I know what to buy. Or should I sell the DP and upgrade the entire exhaust?

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    Master Baiter EJ257's Avatar
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    2.5" at the downpipe/catback junction
    2005 WRX STi (Mods | Virtual Dyno)

    Resident Tuner @ WTF Tuning, LLC

    "Never trust anything that bleeds for a week and lives ..."

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  4. #3
    Registered User Wussola's Avatar
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    Depends on what you buy for a CBE. I have a Cobb DP and a Borla CBE. They match up perfectly and I have no decrease performance with my set up (considering the 3" downpipe tapers to 2.5" and then my CBE starts at 2.5" and expands to 3"). I've heard that it might give you more low end torque (this is unproven though). Off the top of my head the Borla and the Cobb CBE systems will match up with a 2.5" downpipe. Also, if you purchased a 3" CBE (like Invidia) you can always get a converter to match up the Cobb DP.

    I guess long story short ... if you have the Cobb downpipe and acquired it at a good price - it's a quality part - so use it. Anything under 400 WHP you shouldn't notice a difference.
    2011 Subaru Impreza WRX (Premium) | EFI Logics Tuned Stage 3 | Cobb SF CAI | Invidia EL Race Header | Cobb Catted Downpipe | Borla CBE | PW TMIC | Grimmspeed EBCS | Grimmspeed AOS | DW 65C Fuel Pump | Grimmspeed Light Weight Pulley | SPT Short Shifter | JNA Front Lip | EPIC Performance Springs | SMY Cluster w/ Boost & Oil Pressure

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    Surprisingly that answered my question to the point thanks!

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