Gutted primary cats, anybody done it?

[europower]

As the title states. I have done this on my E60 M5 with great results. With that car I saved a ton of money. With the M3 I wouldn't save too much, but I could still put a couple of hundred bucks in my supercharger fund... it also seems a lot easier then it was on the M5... Any experience with this? Thoughts?

[8k3]

Buy an xpipe. if you ever want to put your cats on for whatever reason (move to a state emission testing is required, sell the car, etc) you are in trouble. Xpipes are not that costly. I had a MS catless xpipe, loved it, but selling it because I moved to headers

[W Cole]

You're going to have to cut off the cats. Gut them and then weld back on, correct? I thought about going this route just so everything would look OEM but ended up buying a 2nd x pipe and doing test pipes.

[Bomiz]

Yeah you can find quite a few x pipes and test pipes used for pretty cheap.

[Dave07997S]

Not to mention you can always weld the OEM cats back on the OEM Xpipe.

Dave

[spool twice]

I did, turned out well.

[Sered]

Testpipes are pretty cheap. And its very easy to weld the oem parts back on if you remove them. Any exhaust shop can handle the work without issue.

[europower]

Originally Posted by spool twice

I did, turned out well.

How did you go about it? Any tips?

I'm aware of test pipes, x pipes. They are cheap and maybe a better alternative for some. The route I want to take is the best option for me, as it worked out great on the M5... why pay any money extra when to can have the same result (hp gain) this way...?
I'm not worried about emissions etc.

[europower]

Originally Posted by W Cole

You're going to have to cut off the cats. Gut them and then weld back on, correct? I thought about going this route just so everything would look OEM but ended up buying a 2nd x pipe and doing test pipes.

Along those lines, yes. I might just use the exhaust clamps to secure them back...

[spool twice]

Originally Posted by europower

How did you go about it? Any tips?

I'm aware of test pipes, x pipes. They are cheap and maybe a better alternative for some. The route I want to take is the best option for me, as it worked out great on the M5... why pay any money extra when to can have the same result (hp gain) this way...?
I'm not worried about emissions etc.

I had it done for free at a friends shop, so I wouldn't know how to. However, they are metallic cats, so you'd basically just drill the crap out of the core and take a wire brush to remove the remains.

[StealYourFace]

But test pips and take your oem cats to the junk yard and get 100 bucks ea for them. Pays for your mod

[Sered]

Originally Posted by europower

How did you go about it? Any tips?

I'm aware of test pipes, x pipes. They are cheap and maybe a better alternative for some. The route I want to take is the best option for me, as it worked out great on the M5... why pay any money extra when to can have the same result (hp gain) this way...?
I'm not worried about emissions etc.

You won't though. Cats even when gutted can cause a lot of flow turbulence due to the irregular shape; not only affecting the power output a little bit but also the sound. The reason it 'works' on your M5 is because the cats are part of the headers whereas on the M3 they are part of the X-pipe assembly. People gutted those cats because headers were major money. If they had a test-pipe option, you could bet that no one would gut their S85 cats at all. Permanently gutting your cats will make it harder to sell, it will smell worse than a straight test pipe, and more expensive to get back to stock. All to save a couple hundred dollars.