BCS decat vs sports cat

[Martin_jk]

Has anyone on here changed there BCS turbo back exhaust system with 200cel sports cat to a decat or the other way round? Reason I ask is I'd like to know if there is a big difference in noise level as I'm finding my decat system very noisy especially on tick over! It's a sport system which I know is the louder one of the two but didn't expect it to be as loud as it is, and before I go and spend money on a sports cat I need to know it will be quieter!


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[Flyingscotsman]

Not sure about noise, but the 200cell sports cat saves hassle at MOT time

[ROH ECHT]

Oem cat vs sport cat vs open/decat on a 3" turbo-back exhaust:

[Martin_jk]

Not sure about noise, but the 200cell sports cat saves hassle at MOT time

Yeah I did think that myself tbh mate, probably worth doing it for that alone!


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[Martin_jk]

Oem cat vs sport cat vs open/decat on a 3" turbo-back exhaust:

Thanks for the video mate, can tell the decat is deffo louder just hard to tell on tick over and normal driving! Might just have to take a gamble..


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[r5gtt]

Guaranteed the de cat is louder than the sport cat which should be obvious in sound as there's no restrictions with the de cat.

[AJP]

I wouldn't say a decat is necessarily louder than a sport cat, maybe a touch, but the main difference I notice is the tone of it. A decat has a more 'metallic' noise. A bit like if you took two identical music tracks and messed about with their frequencies - turn the higher 25% of frequencies down to zero but keep the mid and bass the same, and that's what going from a decat to sport cat is like. It'll seem quiter, but it's more a case of certain frequencies being muted. I wouldn't use the term 'restriction' generally; the better sport cats seem to flow just as well as their decat equivalent.

[r5gtt]

Do you think so AJP
I agree with the more metallic sound but Remembering the de cat is straight through and the sport cat has the gauze that doesn't allow gases to flow as quick imo so it is a restriction of some sort.

[Martin_jk]

Guaranteed the de cat is louder than the sport cat which should be obvious in sound as there's no restrictions with the de cat.

That was my thoughts too I assumed it would be louder with a decat as it is straight through pipe! Just really confused and don't want to spend out on a sports cat and still be too loud!


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[r5gtt]

Guaranteed the de cat is louder than the sport cat which should be obvious in sound as there's no restrictions with the de cat.

That was my thoughts too I assumed it would be louder with a decat as it is straight through pipe! Just really confused and don't want to spend out on a sports cat and still be too loud!


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have you got a resonator fitted before the back box?.

[Martin_jk]

I wouldn't say a decat is necessarily louder than a sport cat, maybe a touch, but the main difference I notice is the tone of it. A decat has a more 'metallic' noise. A bit like if you took two identical music tracks and messed about with their frequencies - turn the higher 25% of frequencies down to zero but keep the mid and bass the same, and that's what going from a decat to sport cat is like. It'll seem quiter, but it's more a case of certain frequencies being muted. I wouldn't use the term 'restriction' generally; the better sport cats seem to flow just as well as their decat equivalent.

Thanks for the reply AJP, so maybe it won't make much difference maybe I'll have to change the silencer to the prestige too! Nightmare lol it does sound awesome just can't live with it everyday!


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[Martin_jk]

Guaranteed the de cat is louder than the sport cat which should be obvious in sound as there's no restrictions with the de cat.

That was my thoughts too I assumed it would be louder with a decat as it is straight through pipe! Just really confused and don't want to spend out on a sports cat and still be too loud!


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have you got a resonator fitted before the back box?.

Yes I've got the powervalve sports system so it has 2 resonators, one with the valve and the other next to the down pipe!


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[ROH ECHT]

I removed the cat from my TB and it is noticeably louder and has that different tone spoken of. I do have one Borla so not terribly loud. If you think you might want to run it catless at times...you can install the cat with v-band...it just costs more. I live outside DEQ/MOT range for testing and have no need to swap back and forth to pass and run leaded race fuel...but if I lived within the range of testing I would run a cat.

[AJP]

I wouldn't say a decat is necessarily louder than a sport cat, maybe a touch, but the main difference I notice is the tone of it. A decat has a more 'metallic' noise. A bit like if you took two identical music tracks and messed about with their frequencies - turn the higher 25% of frequencies down to zero but keep the mid and bass the same, and that's what going from a decat to sport cat is like. It'll seem quiter, but it's more a case of certain frequencies being muted. I wouldn't use the term 'restriction' generally; the better sport cats seem to flow just as well as their decat equivalent.

Thanks for the reply AJP, so maybe it won't make much difference maybe I'll have to change the silencer to the prestige too! Nightmare lol it does sound awesome just can't live with it everyday!


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I reckon doing that would be a better option than changing the downpipe.

[AJP]

Do you think so AJP
I agree with the more metallic sound but Remembering the de cat is straight through and the sport cat has the gauze that doesn't allow gases to flow as quick imo so it is a restriction of some sort.

Yes, logically that would seem the case. Physics and that. But... going by my Stage 2 dyno, it made 345lb/ft on the stock pump and pretty much stock everything else. I haven't seen or heard of cars with the same setup but with a decat making significantly more peak or at least enough to say a decat is objectively better. Although there's a chance a decat might make a tiny bit more at higher revs. The Powervalve cats are oversize, to compensate for any inherent restriction. I'd imagine a sport cat that didn't benefit from a good design in order to compensate would indeed be more restrictive than its equivalent decat.

So maybe we're both right