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As the title states - I am working on a possible project for a cat-back muffler delete system for the Mk6 Golf TDI that would also have the option to exit in the GTI split-dual manner. It would save time if someone could confirm the outlet diameter of the DPF where the exhaust connects. On the GTI this is 65mm - we are working on the assumption that the TDI is 60mm. Can anyone here confirm that assumption?
 

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As the title states - I am working on a possible project for a cat-back muffler delete system for the Mk6 Golf TDI that would also have the option to exit in the GTI split-dual manner.
Well according to RPS99SHO the GTI rear box fits, which may have read. ;)

Mufflerectomy and Lowered
 

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Discussion Starter #3
Well according to RPS99SHO the GTI rear box fits, which may have read. ;)
Yes, that is fairly well known. But I am looking into the possibility of replacing the entire system, not just the rear silencer. I know of at least one person here in the states that has replaced his complete TDI system with the same from a Mk6 GTI. The entire system fits up just fine, except the pipe diameter of the GTI system is larger than the TDI, so a bit of modification at that joint was needed. I'm looking to try to avoid local fab work - what I am after is a simple bolt-on system. So I need to know for certain what the diameter at the very front is. If I no one knows it, I'll need to schedule a time to get under my car and physically measure it.
 

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Are you talking about splicing in from the DPF back? To be street legal you would have to splice in from the H2S converter back. There's also the backpressure valve and sensors back there. I'm not sure if you can bypass those things without throwing lots of check engine lights. How did this other person get around the CELs?
 

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Discussion Starter #5
My bad, Chitty. I had assumed (wrongly, apparently) that the DPF was the last item in the string. I'm not talking about removing anything from that point forward, just the exhaust from the final cat (or whatever) back. It has been my understanding that the connection from cat-to-pipe is in the same location for both TDI and GTI, but the GTI has larger diameter pipe.
 

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If I understand correctly, the TDI has 3 cats, the last just ahead of the muffler. What is the point of replacing the muffler with a pipe, after the cats a valve and a filter?
 

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Discussion Starter #7
Several reasons. None are very compelling singularly, but if you want/need more than one of the results, it may be worth considering.

  • Possible minor loss of a few pounds curb weight.
  • Very slight (really small) change in exhaust note (deeper).
  • Some very small possibility of better fuel economy with larger, free-flowing pipe.
  • Convert to GTI-style dual rear exhaust (appearance, and/or to allow use of a better concealed receiver hitch).
 

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Yes, that is fairly well known. But I am looking into the possibility of replacing the entire system, not just the rear silencer. I know of at least one person here in the states that has replaced his complete TDI system with the same from a Mk6 GTI. The entire system fits up just fine, except the pipe diameter of the GTI system is larger than the TDI, so a bit of modification at that joint was needed. I'm looking to try to avoid local fab work - what I am after is a simple bolt-on system. So I need to know for certain what the diameter at the very front is. If I no one knows it, I'll need to schedule a time to get under my car and physically measure it.
I am one who is also looking to completely overhaul my exhaust. I just did a mufflerectomy today and was severely disappointed when there was not even a 1dB increase in sound. Further research led me to the complex emission system that a TDi has and i knew why it was still quiet. However, what can be cut out and what can't from the rear muffler forward. Also, I was assuming that as long as anything rear of a sensor was removed I would be safe. If this is not the case please do tell as I am new to TDi's. In addition any information of a successful boomin TDi exhaust is welcome.
 

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Thanks very much for that link. IMO, there's too much technology on this thing, but since I can't have a car that will function correctly without it, I'll have to live with it. My question however is if i take off that H2S catalyst, will it be louder? Seems to me that that the DPF will basically mute the car without all the other catalyst.
 

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Discussion Starter #12
Follow up - The TDI outlet diameter at the pipe connection after the H2S catalyst is 55 mm O.D. I don't yet know how that compares to the Golf 2.5, but it is smaller than the GTI, which is 60 mm O.D.
 
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