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Discussion Starter #1
For those of you that have clogged up your catalytic converters or overheated and damaged them/blew out chunks, etc., which cats were affected? Was it the primary cats up near the exhaust manifolds, or was it the secondary cats?

I have clogged up my Bank 2 cats to the point that the motor won't even rev past 3000 RPM in neutral. It sounds like someone pounded a potato into the pipe. Car will only go about 45 MPH and it throws all kinds of codes. I plan on replacing the primary cats with B&B test pipes, but I'm not really sure if it is the primaries or secondaries that typically get destroyed via extended WOT runs with pullied cars. Anyone know?
 

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Primary cats are the ones that let go, however, it’s very likely that the debris was collected up against your secondary cats.




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This^

I’d recommend just taking the cats off quickly an looking since you can’t drive anyway. It’s like 4 bolts. And gut them while your at it, B.B. test pipes don’t fit great and aren’t worth the 450 imo. I wouldn’t buy them again.
 

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This^

I’d recommend just taking the cats off quickly an looking since you can’t drive anyway. It’s like 4 bolts. And gut them while your at it, B.B. test pipes don’t fit great and aren’t worth the 450 imo. I wouldn’t buy them again.
Or just go full exhaust and call it a day. Never understood the test pipe thing. That's a lot of cash for some small sections of pipe.
 

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Discussion Starter #5
Car has a Corsa cat back on it. It was that way when I bought it. What’s the easiest way to gut the secondaries? The primaries seem easy enough. I really want to shove a .410 shotgun with rat shot in there and just blast it out. The substrate is brittle enough that it would likely break up into a million pieces (you guys just watch, my next post is gonna be: For Sale: 2009 CTS-V, hole in floorboard, clogged cats, leaky exhaust — make offer).


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Car has a Corsa cat back on it. It was that way when I bought it. What’s the easiest way to gut the secondaries? The primaries seem easy enough. I really want to shove a .410 shotgun with rat shot in there and just blast it out. The substrate is brittle enough that it would likely break up into a million pieces (you guys just watch, my next post is gonna be: For Sale: 2009 CTS-V, hole in floorboard, clogged cats, leaky exhaust — make offer).


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Well Corsa doesn't make a cat back for the V2 so either it's custom or just an axle back. Primarys are your biggest concern.
 

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Discussion Starter #7
Well Corsa doesn't make a cat back for the V2 so either it's custom or just an axle back. Primarys are your biggest concern.

That is correct: it is an axle back. The Corsa retains that nice crappy crimped mid-section with secondary cats.
 

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Headers FTW.

Just don't buy from Maryland speed. Ever.

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Discussion Starter #9 (Edited)
Well I pulled my exhaust off and checked and both the primary and secondary on Bank 2 were plugged solid. It looks like the primary started disintegrating and then packed up into the secondary. The ECM tried to compensate by making it as rich as it could and added soot to further cement it all together.

So now I have all 4 cats in place, but they are just a former shell of themselves.......

So my exhaust is factory pipes with hollow cats to Corsa mufflers. Man this thing is loud! I'll likely have to put resonators in.
 

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Discussion Starter #11 (Edited)
First I jacked up the car as high as I could and used 4 jack stands. I end up with the car about 30" off the ground. The primary cats are easy -- you don't even have to take the primary pipes off the car. Once you have removed the mid section, you can use a large screwdriver and a mallet to break up the substrate. Once you get them started coming apart, you can just keep poking them with the screwdriver and pieces will keep coming out. After it was all broken up, I fired it up and used the engine exhaust pressure to blowout the dust. Neighbors must have loved me at that point.

The secondaries were a bit more work. I ended up cutting off the curved section of pipe in front of the cats with a cut-off saw. I left about 3/4" of pipe still sticking out of the cats. Gutting them was very easy using the same previous hammer and screwdriver. When it came time to put the exhaust back together I put a 4 inch length of slightly larger diameter coupling pipe on the outside of where I sawed the pipe in two and used u-bolt clamps to hold it all together (until it can be welded). Since I will likely add resonators, I'll wait to have it welded when I have those installed. I could easily do it all myself, but my MIG welder is on the fritz and needs a new motor-driver board. I'll likely just go to a local muffler shop.

Total cost in parts was about $20 for the two little sections of coupler pipe and 4 u-bolt clamps. The whole job took about 4 hours.
 

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Will gutting the primary cats throw a code or light? Obviously, the code/light could be corrected with a tune, but I might do this sooner if there is no codes thrown..
 

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Will gutting the primary cats throw a code or light? Obviously, the code/light could be corrected with a tune, but I might do this sooner if there is no codes thrown..
yes, it likely will throw a code for catalyst efficiency
 

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I probably should've gutted my cats instead of doing test pipes. Now I have to argue with myself over buying ARH headers or gutting and reinstalling cats and selling the BB Test pipes.
 

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How or why did they clog?
 

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Discussion Starter #18 (Edited)
They overheat from pushing to much high temp exhaust through them due to the increased boost which makes increased exhaust and increased heat. They then start to melt a bit. Once they start to melt, they are no longer a nice honey comb, but instead turn into globs of melted material that further clogs them and makes them run hotter and hotter. Eventually, bits and pieces come apart and then they travel further down the line where they clog the secondaries. That's when you notice it, as the motor won't run right.
 

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New to the forum here. But this just happened to me last week. It was a hot outside and I had been in traffic for a bit then caught a break in traffic. At the same time a Porsche was coming by... You know the rest..

I run 2.38 upper, CAI, and E85 but at the time I was on pump gas. Once I got off the freeway I knew something was wrong. My car shut off in the driveway.

This post helped me figure out what was going on. Thanks guys.

I have some kooks green high flows on the way now. Any good recommendations for muffler shops in Houston, Tx?
 

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having cat over temp disabled in the tune likely speeds the melting along as well.
 
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