Product Reviews

CTS Turbo Secondary Cat Delete Pipes + Zip Tie Mod for TTRS

The 5 cylinder turbo engine of the TTRS has one of the most unique and enjoyable sounds in the entire Audi lineup; when the engine reaches 4,000 RPM or higher, the note is particularly deep and pleasant and the driver can’t help but smile ear to ear. My goal for this car has always been to keep it OEM Plus, so I was hopeful that the “Sport Exhaust” option would be sufficient to amplify the sound and not need to be replaced or modified. Upon further research, the sport exhaust is pretty much the same as the OE exhaust but with different mufflers to allow slightly more sound, and black exhaust tips instead of chrome – it’s not really a “true” performance setup, and even in Sport mode it’s not really much louder either. On the other hand, aftermarket exhaust options from AWE, Borla, and Corsa are both expensive (generally well over $2k USD with tax and shipping), and a little louder than I’d like for a daily driver. When I saw CTS Turbo was having a Summer Sale on their secondary cat delete pipes for less than $300 that could be installed in under an hour, I figured why not give them a shot and see if this was the in-between solution I was looking for.

I ordered from Modded Euros and they arrived about a week later, coming in at $280.49 with 20% off and free shipping, no tax. The box was huge, but fits inside of the trunk no problem. With the San Diego heatwave going on, I had my friends at Big Fish Motorsports put the car on the lift and install for me, finishing the job in about 30-45 minutes while taking his time to ensure fitment. The install was very straightforward and definitely DIY-able, simply remove the bolts that clamp the OEM mid-pipes on, and then use the supplied hardware to connect the new pipes. You can see before & after shots below, it’s a straight-up replacement for the stock mid-section just a little shinier and without the secondary cats, and with a large bend removed to improve flow.

The pipes did not trigger a CEL for me, although that may be due to the APR tune I have. Because the first set of catalytic converters are retained, there is no noticeable difference in smell, and I doubt much of a difference in emissions output either. After a month of driving, I have not noticed an increase in soot from the exhaust pipes or any other indications that the emissions were negatively impacted. Because I live in California, these shiny pipes might fail the visual inspection component of emissions testing, but I’m not due for another 18 months or so and hopeful that by this time, the pipes will blend in a little better. Worst case scenario, I can swap the OEM midpipes back on, get tested, then put these right back on, and probably only look at around an hour of labor to do so. Easy fix…

Okay, okay – the important part you’ve been waiting for…the sound. Surprisingly, these small, cheap pipes make a big difference. I’d say the exhaust is about 20% louder in both regular and “S” modes, which is about exactly the right amount for a daily driver to get that performance sound without being annoying. Regular mode sounds a lot like the Sport mode did before, and Sport mode sounds even better. Regular mode is great as a daily driver, still produces no drone, and just has a little bit more sound without ever being obnoxious. I have numerous video clips below with sport mode off and windows both up or down, at low speeds and high. If you’re not using the gas much, the exhaust sounds about the same with sport mode off – and if you’re really pushing it, it wakes up. Sport mode also sounds about 20-30% louder/better, without ever being crazy. At slow speeds you sometimes get a bit of a gurgle, especially when turning, and you can hear the noise come on a little earlier in the RPM band than otherwise. When you’re pushing the car, it sounds even more fantastic. I did not happen to get “before” sound clips, but grabbed some audio of my car after the modifications for you to hear the fantastic sound it produces now:

CTS Turbo claims this section of pipe also increases power by +7 whp and +10 ft/lbs of torque, which I have not dyno tested to verify but seems reasonable enough to be true. Even with zero gains I’d say this is worth it for the improved sound alone, but <$300 for both better power and sound? That’s probably some of the best ROI I’ve ever gotten from a mod, ever. A few other brands make these including Miltek, AWE, and 42 Draft Designs. They’re all around the same price and likely of similar quality, so buy whichever you like – at the end of the day these are just simple pieces of stainless steel with the sole aim of removing a restrictive (and largely unnecessary) secondary set of catalytic converters. As someone who considers themselves an environmentalist, the minimal impact this would have on the environment is easily offset by other carbon reducing actions I can take such as eating lower on the food chain, carpooling to work, and using solar power for my home, all three of which I already do.

In summary, it’s a super cheap mod that can be installed in less than an hour, and greatly improves the sounds of the car without ever being overkill. Bang for the buck, this is one of the best mods you can do for this car, and seems like a no-brainer for pretty much an TTRS owner that wants a little more sound and power (and who doesn’t want that?).

Bonus: The Zip Tie Mod

If you want a little extra sound on top of the secondary cat delete, While you’re down there, it’s also a good time to do the zip-tie mod. What’s the zip-tie mod you ask? Easy, just locate the vacuum hose just behind the driver’s side exhaust tip that controls the valve that opens/closes the exhaust for more noise in sport mode…if you simply zip tie a kink in the hose, the valve is always open – which means more sound! Even in sport mode the exhaust valve is not open until a certain RPM (around 3,000 RPM, I believe) so this makes lower RPMs significantly louder, while higher RPMs are unchanged. It sounds great, and allows you to have the sport mode sound without having to to turn on sport mode and get the sport mode ride stiffness. It also produces a little more crackling & popping at low speeds, which is pretty badass if you ask me. Best of all, simply cut the zip tie off to reverse it if you ever get tired of it. Below is a zoomed out picture so you can get a better idea of the location:

Nick Roshon

Nick has been an Audi owner and fanatic for the last 10 years, and started Nick's Car Blog in 2009 to share DIYs and pictures of his A4. Currently he drives a 2012 Audi TT-RS, and has previously owned a B7 S4, B7 A4, and an 82 Audi Coupe (GT) LeMons race car. In his day job, Nick is a digital marketer and lives in San Diego, CA, USA.


  1. I found in Militek 2.5 ” but your’s 3’’ I want to know if you feel an improvement in a throttle response.Because Militek guarantee that. There is a better response with the 3’’ ? Thank a lot

  2. Hi Ricardo – I think they’re the same; they’re both intended to work with the stock exhaust. I think they are just measuring from different spots, I think maybe the front part is 3″ and then the back part is 2.5″. All of the secondary cat deletes are pretty much identical.

  3. Hey Nick,

    Is there a particular reason that there’s a kink the one pipe? This seems to be in the same place regardless of brand.

  4. Hey nick, what kind of installation hardware came with your pipes? Did you have to buy anything else? Thx

  5. Hello! Awesome blog, I wonder if you need to have a new tuning to the car if you install these pipes? And does it go through inspection of a car if you know that?

  6. No need to retune, although if you do tune the car this will give more benefit – either way the engine automatically adapts to how much spark, fuel & air it has available so you’ll see gains. In terms of inspections, depends on where you’re located and how strict they are. California (where I live) is one of the most strict states and technically these won’t pass, although you can either (1) swap them back every 2 years for inspection which isn’t that hard to do (1 hour of labor) OR (2) find a place that isn’t paying very close attention, as you’ll probably pass just fine as long as they don’t look directly at it.

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