Question about removing cats?

RikRok

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On the inlet sie of the cat, if I cut just in front of the weld, will the iserted piece of the cat neck slide out. I am doing this at home and am trying to see if I can just get a piece of 2 1/2" pipe to replace the cats.
 

bwhitmore

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I don't believe so. The pipe ended right at the weld to the cat in my case. I cut my cats off about 1/2" header side of the weld at the cat. Left just enough room before the bend to slide my 2 1/2" Roe High Flows over the end and clamp them down with the Accuseal Torca style clamps. No leaks too.
 

hemibeep

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If you grind the weld there may be about 1/4 to 1/2" of pipe inside the cat. then a slight flair on 2 1/2 will slide over the front of the pipe. A straight piece of 2 1/2 will work without a bend.
 

Achilles99

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On the inlet sie of the cat, if I cut just in front of the weld, will the iserted piece of the cat neck slide out. I am doing this at home and am trying to see if I can just get a piece of 2 1/2" pipe to replace the cats.

I'm not sure what your question is... are you asking if you cut the inlet side of the cat, will the outlet side slide out of the catback exhaust? I did that, and replaced the cat with a 2.5" piece of straight pipe, just as you suggested. I flared the inlet side to fit over the flexpipe header pipe, and inserted the outlet end directly into my catback exhaust. The outlet end of the cat is just clamped to the exhaust.
 
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RikRok

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Did you just go to a exhaust shop and buy a couple pieces of pipe and have them pre flare it, and what type of clamp to I need to pick up? How large do I need to tell them to flare it to?
Thanks
 

Schulmann

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Very easy to replace the stock cats with a straight pipe though it requires a welder if you want to do a clean job. You can get along without the welder but he job will not be as "nice".
 

hemibeep

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The pipe is the exact same size as a 2 1/2 pipe. Just have them flair it enough to slide over itself. I took it down to a muffler shop and they did it for free! I tried a wide flat band clamp and it did not "squish" the pipes enough causing a leak. then went with the old style U-bolt 3/8" HD and it did "squish" enough. As Schulmann said though, it does look kinda hokey. After hearing it, with corsa system, it is too loud and now I am going to go with high flow cats and weld it for a clean look.
Also IMO it smells like the old roadrunner exhaust without the cats on and I want to get away from that.
 

Achilles99

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Did you just go to a exhaust shop and buy a couple pieces of pipe and have them pre flare it, and what type of clamp to I need to pick up? How large do I need to tell them to flare it to?
Thanks

Yes, that's exactly what I did. Cut the cat leaving yourself as much of the curved flex pipe as possible (the straight part of it), and measure the distance from there to the exhaust (leaving yourself a couple of inches to slide the flared part over the flexpipe). Autozone sells a precut 18" piece, but that was too short for stock applications.

Definitely use a u-clamp, and not flat band clamp. Mine leaked as well with the flat band clamp. I also bought one of the muffler mending kits (the kind that you dip "bandages" in water, which hardens into a cast) and wrapped the joints. No leaks.

I have the Corsa, and I like the sound. I thought the sills were still too hot after using hi-flows.
 

Schulmann

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If you remove the cats it is better to keep the stock muffler otherwise the car will be very noisy. Stock muffler also helps to conceal that you don't have cats. It VERY illegal to remove cats in some States. The only real advantage that I see in running without cats is the reduced cockpit temperature. For more HP there are better things to do than this illegal act. At VOI I ran without cats but I put back them once I got home. So if you do a clean job you can remove them when you really need.
 

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