gain in power by removing catalytic converter

[Wagner]

Originally Posted by codered

Thank you very much for the answer.

However, if the "cat" is defective, removing them still doesn't gain the extra hp I mentioned?
What about the sound? Will it be any different (eg close to 4,6is or 4,8is sound?)
What is the realistic hp gain from removing the cat?

There will be no noticeable gain, maybe 1-2 hp, nothing worth causing check lights. Sound will be barely different as your mufflers are still the same.

[Gary92]

Originally Posted by Wagner

There will be no noticeable gain, maybe 1-2 hp, nothing worth causing check lights. Sound will be barely different as your mufflers are still the same.

im pretty sure the sound would be completely different without a cat

[N S]

In the mustang world we have MIL eliminators for off-road x pipes that eliminate the cats. Essentially they just jump out the connection so the computer thinks everything is working as designed. Not sure if BMWs have something similar.

As for removing cats for performance gains - yes, there are gains to be had. Cats are extremely restrictive. A more environmentally friendly mod may be to find a set of "high-flow" cats that flow better.

IMO the gains don't justify the hassle though. Maybe on a street/strip car, but not on an X5.

[Wagner]

Originally Posted by N S

In the mustang world we have MIL eliminators for off-road x pipes that eliminate the cats. Essentially they just jump out the connection so the computer thinks everything is working as designed. Not sure if BMWs have something similar.

As for removing cats for performance gains - yes, there are gains to be had. Cats are extremely restrictive. A more environmentally friendly mod may be to find a set of "high-flow" cats that flow better.

IMO the gains don't justify the hassle though. Maybe on a street/strip car, but not on an X5.

Agree, with added modification. Cats alone are not worth it, no matter what you have.

[E61Silver]

Originally Posted by Gary92

im pretty sure the sound would be completely different without a cat

So that's a reason to do it

[Wagner]

Originally Posted by Gary92

im pretty sure the sound would be completely different without a cat

Pretty sure you're wrong unless by completely different you mean, crap. I've modified many cars [BMW M3s, X5s, 545, 645, 350Z, Mustangs, etc], unless the mufflers (which actually MUFFLE the sound) and pipes are changed the only difference will be noise, not a great sound

[codered]

Originally Posted by Wagner

Pretty sure you're wrong unless by completely different you mean, crap. I've modified many cars [BMW M3s, X5s, 545, 645, 350Z, Mustangs, etc], unless the mufflers (which actually MUFFLE the sound) and pipes are changed the only difference will be noise, not a great sound

By changing the "mufflers" you mean changing the entire exhaust system or just parts of it?
I'm guessing the mufflers are just the 4 metal pipes at the end of the exhaust? Will larger one make any difference?
Sorry about my poor understanding of english, I'm not a native speaker.In romanian dictionary "muffler" refers to the whole exhaust system which I suppose is wrong/incomplete.