Gutting stock cats

[bmbmw66]

Hi guys, has anyone gutted the stock cats here before? Don’t feel like paying a ton for downpipes, and the offer I got for my stock cats was like $200 for both.

I’m thinking about just gutting the stock ones. I don’t care about needing them again. Is this a good idea?

My only concern is that the hollow pipe after gutting might be too wide at the center (where the old catalytic material was). Would this matter? Thanks

[m5rosco]

Originally Posted by bmbmw66

Hi guys, has anyone gutted the stock cats here before? Don’t feel like paying a ton for downpipes, and the offer I got for my stock cats was like $200 for both.

I’m thinking about just gutting the stock ones. I don’t care about needing them again. Is this a good idea?

My only concern is that the hollow pipe after gutting might be too wide at the center (where the old catalytic material was). Would this matter? Thanks

They make the best decats you can get! Guaranteed to fit perfectly, and the fact they are double walled means you don't hear the common waste gate rattle that often becomes apparent after fitting normal decat pipes.

I too was concerned about flow but my tuner told me he's done hundreds of m5's, some with gutted cats, some with "proper" decat pipes and it makes no difference at all, on the dyno or the road.

The only downside is not being able to be paid for scrapping them, but if they're only making $200 then I wouldn't worry. At one point here in the UK they were making the equivalent of $1500, apparently they're around $500 recently though.

[bmbmw66]

Originally Posted by m5rosco

They make the best decats you can get! Guaranteed to fit perfectly, and the fact they are double walled means you don't hear the common waste gate rattle that often becomes apparent after fitting normal decat pipes.

I too was concerned about flow but my tuner told me he's done hundreds of m5's, some with gutted cats, some with "proper" decat pipes and it makes no difference at all, on the dyno or the road.

The only downside is not being able to be paid for scrapping them, but if they're only making $200 then I wouldn't worry. At one point here in the UK they were making the equivalent of $1500, apparently they're around $500 recently though.

Thanks for the response man and I agree with your points. Do you have a gutted cat on yours? The double walled keeping the waste gate rattle is definitely great, but I’m wondering if it’ll also reduce the turbo spool
Sound that comes with downpipes. If you have it on yours or have heard it how does it compare?

[m5rosco]

Originally Posted by bmbmw66

Thanks for the response man and I agree with your points. Do you have a gutted cat on yours? The double walled keeping the waste gate rattle is definitely great, but I’m wondering if it’ll also reduce the turbo spool
Sound that comes with downpipes. If you have it on yours or have heard it how does it compare?

Yes I do have gutted stock cats on my f10 m5. This is my second f10 m5. My first had regular aftermarket decat downpipes. Both setups sound the same to me from an exhaust point of view. Plenty of turbo spool sounds. Only difference is there are no waste gate rattles on the current car!

[bmbmw66]

Originally Posted by m5rosco

Yes I do have gutted stock cats on my f10 m5. This is my second f10 m5. My first had regular aftermarket decat downpipes. Both setups sound the same to me from an exhaust point of view. Plenty of turbo spool sounds. Only difference is there are no waste gate rattles on the current car!

Sounds good man. Do you have videos of it?
And after going catless did you get any more pops / crackles? Anything else you noticed as to change in sound / performance before tuning ?