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      05-19-2019, 03:43 PM   #1
ikenjoku7
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Gutting stock pipes but keeping cats

I would like to go stage 2 but don't want to deal with the headache from the smell and emissions that I'd deal with if I went catless, so I want to go with high flow catted dps. However, I don't see much of the point in buying an aftermarket set so I'll be gutting my stock downpipes myself. My question is will it be possible for me to remove just the primary cat and make the dps high flow(400 cell I think)? I don't know much about downpipes or cats so Any insight will be appreciated.
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      05-19-2019, 04:01 PM   #2
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Quote:
Originally Posted by ikenjoku7 View Post
I would like to go stage 2 but don't want to deal with the headache from the smell and emissions that I'd deal with if I went catless, so I want to go with high flow catted dps. However, I don't see much of the point in buying an aftermarket set so I'll be gutting my stock downpipes myself. My question is will it be possible for me to remove just the primary cat and make the dps high flow(400 cell I think)? I don't know much about downpipes or cats so Any insight will be appreciated.
I've been thinking about this myself, it is possible, it all comes down to have careful you are when opening them up. I'd say the best way to do this is to work out where one monolith ends and cut open the cats, obviously marking the orientation first. If you were to go the caveman approach and chisel them out you will damage the other monolith.
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      05-19-2019, 04:13 PM   #3
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Originally Posted by Dwaynos View Post
Quote:
Originally Posted by ikenjoku7 View Post
I would like to go stage 2 but don't want to deal with the headache from the smell and emissions that I'd deal with if I went catless, so I want to go with high flow catted dps. However, I don't see much of the point in buying an aftermarket set so I'll be gutting my stock downpipes myself. My question is will it be possible for me to remove just the primary cat and make the dps high flow(400 cell I think)? I don't know much about downpipes or cats so Any insight will be appreciated.
I've been thinking about this myself, it is possible, it all comes down to have careful you are when opening them up. I'd say the best way to do this is to work out where one monolith ends and cut open the cats, obviously marking the orientation first. If you were to go the caveman approach and chisel them out you will damage the other monolith.
I was going to go the caveman method so thanks for that tidbit lol. What would be the best way to cut the cats open?
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      05-19-2019, 04:23 PM   #4
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You would have to be extremely careful if you were to chisel them out, depends how much gap there is between the two. Keep checking all the time. If you opt for cutting open I would just use an angle grinder, cut all the way around in between the 2 monoliths, knock the 600cell one out and weld back together.
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      05-19-2019, 04:28 PM   #5
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Originally Posted by Dwaynos View Post
You would have to be extremely careful if you were to chisel them out, depends how much gap there is between the two. Keep checking all the time. If you opt for cutting open I would just use an angle grinder, cut all the way around in between the 2 monoliths, knock the 600cell one out and weld back together.
Sadly I have no welding tools or experience so how would I know when I've gone all the way through the first monolith?
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      05-19-2019, 04:43 PM   #6
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Sadly I have no welding tools or experience so how would I know when I've gone all the way through the first monolith?
To be fair you will probably have 1" or so of gap. The 2nd o2 sensor reads after the 600cell side of the cat to my knowledge. I'd use a long drill bit, hold it against the side of the cat up to the 2nd o2 sensor hole and mark the drill bit with paint, that way you will know when you're just about there. From there on gingerly chisel the rest out bit by bit from the top. Once you get almost there, keep checking and don't hit to hard. With the gap you should be safe.
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      05-21-2019, 09:57 PM   #7
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Quote:
Originally Posted by ikenjoku7 View Post
I would like to go stage 2 but don't want to deal with the headache from the smell and emissions that I'd deal with if I went catless, so I want to go with high flow catted dps. However, I don't see much of the point in buying an aftermarket set so I'll be gutting my stock downpipes myself. My question is will it be possible for me to remove just the primary cat and make the dps high flow(400 cell I think)? I don't know much about downpipes or cats so Any insight will be appreciated.
I tried with an air chisel. Actually, I had a helper. I thought I told him to go easy and just chisel out the top cat material, but he nicked the bottom of the secondary cat and so went my high flow cat idea. Had to drill it all out and become catless.

It's doable if you're careful.
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