Anyone hollow out their cats
 

Im going to replace my exhaust manifold gaskets this weekend. and i was thining about hollowing out my cats, they already dont work and i have o2 extenders.

just wondering if anyone has removed all the honeycomb stuff inside and if they have and tips or trick to do it?

Thanks!!!

Yes, I did on another cars.

In my experience, I can tell you few things right away:
- it's not difficult to break inner stuff into pieces and shake it out. Pinch point crowbar well with this.
- without installing a spark arresters in place of cats you exhaust will sound rattling.
- without installing a spark arresters in place of cats you downpipe resonators and mufflers will quickly rust and burn holes.

But the problem is that there are no original spark arresters.
All universal aftermarket one require a lot of work to fit them into a place and weld them on the pipes.
Something like this: , but you need to match the ID on the inlet and outlet with original cats.
So the general idea - they need to be installed as close as possible to the place of the original cats.
As I did on the other cars, the original cats were cut off and then spark arrestors welded in the same place with a lot of efforts and swears.
You need a good muffler shop to do that.

Isn't it against the law to do this?

~20 y.o. cats won't do anything good for the car.
But we are not discussing this issue here, but a technical possibility.
It will do some bad things by restricting the flow of the exhaust gases and limiting the engine power.

So your saying if instead of gutting the cats I should get a spark arrestor in place ? I currently have no mufflers and the only reason I'm thinking about a cat delete is I already have a p0420 for my cats and that's why I have a o2 extender. So I'm thinking about just hollowing them out just to be safe in case they are starting to get clogged I rebuilt the motor about 30k ago but the whole car has 230k on it so I suspect the cats are going bad maybe even starting to be clogged. So it's as slow as other cars? I've done a few other cars they came right out and had no issues but I've also done a bike and that cat was so hard we ended up opening it up taking the stuff out and re welding it shut. I just didn't wanna start to get into this and it was super hard to break apart.

I don't know how hard it to break it to a pieces on this car.
I did it before on the another toyota car, and it was piece of cake.
What you mean you have no mufflers?
Is it straight pipes?

I just have the mufflers unbolted so the exhaust ends right after the rear axle.

But you still have middle cat. converter (#3) and two resonators.
I talked about them before, that they will go bad much faster after cats hollowing, because the sparks and temperature increase.

I too am thinking about hollowing out my two upper cats and deleting the third. I want to get headers and have the extra flow. Is there a stainless steel exhaust option that will help slow down the corrosion effects? Also, if the cats are hollowed out will it throw a code or cause any adverse o2 sensing ?

Without special work you will get check engine light with codes P0420 and P0430.

It sounds like it may be too much work for minimal gains.

Aside from the legal aspects, we do not recommend doing this because the big open chamber creates drone/vibration and causes the exhaust to cool and lose velocity.