New CTS Turbo Downpipe, detailed DIY install guide

NOTE: This is for a PWG (Pnuematic Waste Gate) 2013 and earlier N55 with a 3.5″ downpipe, if you have a later model F30 N55, the downpipe is a 4″ and some parts may be different, also other DP’s reuse the mounting bracket, luckily the CTS Turbo PWG DP does not so one less step for us PWG folks. The EWG folks should be able to use this guide as well, just double check your part numbers.


Foreword:

Here is my experience changing out my downpipe. The install pretty intuitive and the steps don’t need to be followed in the same order I did it in but this should give you a good idea of what a fairly inexperienced car guy might go through changing out their downpipe.

It probably took me about 2 hours total work time. 3.5 hours with the kids/wife/life delays factored in


Prerequisites:

Make sure you have the tools required for the job:

Everything I ended up using for the job (you probably won’t need all this)
  • 3/8″ and/or 1/2″ drive socket wrenches (Long and short handle)
  • 3/8″ and/or 1/2″ socket extensions (whole bunch here)
  • Metric open ended wrench set (14mm and a 16mm)
  • Metric sockets (13, 14 and 16mm, take your pick here, I have a history of spending a little more money on these as they will be used often)
  • O² offset removal tool (Here’s the one I used)
  • 1/2″ Breaker bar (I ordered this one after doing this install)
  • Race Ramps (what I use) or a jack (the one I use, extra low profile, solid AF) and jack stands
  • 6mm nut driver (I absolutely LOVE these Wera’s)
  • E10 and E12 External Torx bits (I bought this Lisle set, cheaper options are available on Amazon)
  • Rubber mallet
  • A flashlight (I have this Thru-night USB rechargeable bad boy charging in my glove box at all times, great flashlight for the car)
  • New Upper V-Band
    • Maybe necessary if you strip the nut or if you live in an area where corrosion is a factor (salt for ice/snow) I didn’t need one and reused the old one
    • BMW part #’s 11657620508 & 18307553601
  • New Lower V-Band
    • BMW part #18307620349 (here at ECS, I just ended up getting it at the dealer)
    • This is necessary as it comes with some sort of a crush gasket that can get mangled when disassembling the stock DP, this really should be replaced.
  • Eye protection (lots of road debris in the belly pan)
  • Lava soap, Gojo Soap, fast orange (Thanks colby!)

Optional tools (made it easier for me)

  • Ratchet spinner (Expensive Amazon one here)
    • I picked up a 3 pack at OSH for the price of this single one a while back, has come in handy on a few occasions

Tools I wish I had for the install:

  • Screwdriver hook set or screwdriver pry bar set (I ordered both of these sets after this install)
    • My Upper V-band was very stuck only on one side and these would have made it easier to break it free)
  • A breaker bar (the damn O² sensors were really difficult to break free)
    • I ended up having to straddle the stock CAT to be able to get enough leverage on it to break it free
  • A proper lift
    • The ramps worked well, but there was a lot of heavy pulling/pushing in awkward positions under the car, definitely had some sore muscles in weird places the next day
  • Pair of mechanic work gloves (Still have grit and grease under my nails, 4 days later)

Installation

  1. Pop the hood and remove your engine cover
  2. You need to disconnect the 2 O² sensor wires located towards the top rear passenger side of the engine circled in the next picture
  3. To disconnect just push on the little tab and pull out
      1. No need to mark them as they are pinned differently so you can’t hook them back up incorrectly.
  4. Disconnect the wires from the wire clips all the way down to the CAT, and push the wires down so they won’t get stuck on anything later on
    • My arms/hands are small enough to follow the gray and black wired O² sensor cables almost all the way down to the CAT, just feel around and push to unclip the wire holders
    • Since you can’t see them, these are the types of clips you need to release the cables from. Just push on the top and release them, it’s pretty easy to release them

      The clamps used are similar to this, just made of metal
  5. Get your car up in the air via your preferred method (I used my Race Ramps, which clears the M-Sport package perfectly)
  6. Put your eye protection on and remove the 20+ belly pan screws and the belly pan
  7. Now on the passenger side near the wheel well you will have your big fat catted downpipe
  8. I started by removing the 2 13mm bolts that the stock CAT mounts on to

    The bolts mounting the CAT to the bracket to the frame
  9. Next, I decided to work on the harder part, the top V-clamp
    • This little bastard gets its own subsection
    • It’s really tight in there, and getting the leverage to torque off that nut is tough.
    • My hands/arms are small enough to get in there albeit it’s very tight and awkward
    • I ended up using an open ended wrench to initially loosen the nut, a millimeter turn at a time
    • I then was able to use a 3/8″ socket wrench with a 1″ extension to get through the middle resistance area
    • The combo I used to break the top V-Band nut
    • I then finished with just the a socket spinner to finish off removing the bolt
  10. The top V-Band may or may not now be free, if it’s stuck you need to get creative getting something in there to split it apart. Mine was stuck only on the drivers side. After lots of trying with different methods, I was able to jam a long 18″ 3/8″ socket extension in there and whacked it with a rubber mallet to loosen up the driver side of the clamp. This is where I wish I had a hook tool or pry bar set to make it easier.
  11. Using your E-Torx remove the pictured below exhaust hanger
    • The exhaust will droop down a bit when you remove this but will be held up just fine by a plate towards the rear of the car.

  12.  Now remove the lower V-Band clamp, it’s a 16mm nut holding it on, if you’re using an impact or socket you will need a deep socket for this, I ended up using an open ended ratcheting wrench
    • The lower V-Band clamp
    • If it doesn’t break free (the band doesn’t release, give it a whack with a rubber mallet, it should spring open)
  13. Now with both clamps loose and the exhaust loose you should have enough play to wiggle, push, pull, do whatever it takes to remove the stock CAT. Be careful as your O² sensors are still installed, just gently pull and twist the old CAT out, it isn’t difficult
  14. Now move the O² sensors from your stock CAT to your aftermarket CAT, do one at a time and make sure you know which is the top and bottom of the aftermarket CAT

    Stock left, aftermarket right
  15.  This part sucked, the O² sensors were stuck on there really hard. I didn’t have a breaker bar or a pipe handy so getting enough torque on these little bastards was tricky. I ended up literally sitting on the stock CAT and using the longest socket wrench I had with the O² removal tool to finally break it free. There were lots of choice words used here, enough to make me buy a breaker bar set right after this install
    O²sensors installed
    • Be sure to install the copper crush washer on your O² sensors

      Copper crush washers on the O² sensors
  16. Time to start reinstalling the aftermarket pipe. Here is where you should replace the lower V-Band, the below pictured crush gasket get’s really mangled during the de-installation process as seen:
    Mangled gasket/washer thing in the lower V-Band

    Inside it’s channel
  17. If you’re not the brightest bulb on the tree like myself this is the orientation of the crush gasket thing next to the midpipe
  18.  I started with the upper V-Band, gently positioned it around the bottom of the turbo and then used the new CAT to get leverage to get it seated properly, I tightened it just enough to hold on there without falling on my head
  19.  Attach the lower V-Band to the midpipe loosely (easy peasy)
  20.  Feed your O² wires back up to the top of the engine bay and clip the O² sensor wires where you can, you should be able to easily see these clips now, just try to keep the O² sensor wires away from the very hot exhaust components in the channel.
    • I was able to feed them up using my hands/arms only, if you need to, you can fish a line through from the top of the engine bay
  21. Reinstall your exhaust hanger to full tightness
  22. Since there are two flex sections (CAT and midpipe) aligning these things up was super easy, make sure the top flange is staying flush against the turbo exhaust up top and twist as needed to make the lower V-Band sit flush. I have no idea how much torque is needed on these V-Band bolts but I tightened the shit out of them
    • Make sure everything is seated nice and flush, upper flange and lower v-band
  23. Put everything back together and double check everything
    • O² sensors plugged back in and wires tucked into the wire holders
    • Exhaust bracket bolts nice and tight
    • Upper and lower v-bands on there super duper tight
    • Belly pan secured on
      • Side note: don’t go for a drive without the belly pan on, it’s not fun, ask me how I know….

CTS Turbo Downpipe

Not much to say here, inexpensive, seems to be constructed well, nice welds, flange is flawless, flex section looks fine. Smooth inside with no manufacturing remnants left behind. It lined up perfectly with no issues what so ever.


Lessons learned:

  • The next time I think I will use the remove the tire technique seen in Keiss motorsports video on youtube and here on CTS Turbo’s official install guide.
    • While I was working under it, I definitely said to myself a couple times, I should have done the remove the wheel method.
  • Doing it the way I did above works just fine, but that top V-Band really sucks and it seems like removing the wheel would take the Pain in the Ass level from a 5 down to a 3.

Thoughts:

  • Sound: The sound change is significant, on a cold start it goes from maybe annoying your neighbors to definitely annoying your neighbors, it’s very bass heavy and screams for a bit on the cold start. The burbles are much louder, snappier and pronounced but it’s not obnoxious
  • Smell: Verdict is still out on this, I tend to smell things others do not, I just have one of those noses and so far the smell really isn’t that bad. Slight smell of a on old carb’d car running rich but it’s really not bad at all so far.  The wife hasn’t mentioned the smell yet so that gets a pass in my book.
  • Performance: The butt dyno says the car feels a bit more responsive now, seems to rev quicker and have a little more pep in it’s step
  • That’s all, you’re done, now go enjoy the sweetness of an aftermarket Downpipe!
  • If this helped please use any of my Amazon links on your next Amazon purchase, any little purchase helps! Thank you!
2 comments Add yours
  1. Had the same experience w/ rhino ramps, but it sounds like I’m little “thicker” than you so everything was cramped/borderline claustrophobic. I went after it in my driveway in LA; when I started, it was clear, and just as I was getting the new DP linked up to the through, a monsoon broke out, leaving me wet, cold, and on my back underneath the car… after dark.

    Oh I forgot about the O2 sensor tool halfway through (nice), so I had to get an Uber to Harbor Freight to get an adjustable spanner, covered in oil, and wet haha

    Doing so forced me to finish up with a flashlight in my mouth and essentially licking the belly pan clean and catching all the debris in my mouth…

    Pro-tip: add Lava Soap to your pre-reqs.

    1. Hahaha, yikes, sounds like it was good time!
      Good for you, persevering through it! Thanks for sharing!

      I was by no means comfortable under there, it is tight but doable. after shredding through my 3rd pair of latex gloves I gave up on them, I had muscles hurting in places I didn’t know there were muscles the next day.

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