MK5 Golf GTI
All Things Mk5 => Mk5 General Area => Topic started by: Martin_jk on October 26, 2016, 06:49:42 pm
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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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Not sure about noise, but the 200cell sports cat saves hassle at MOT time
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Oem cat vs sport cat vs open/decat on a 3" turbo-back exhaust:
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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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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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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.
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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.
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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.
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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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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?.
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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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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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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.
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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.
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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
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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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wow and you're still saying it's too loud?.
I have a BCS DP and sport cat linked with a link pipe into milltek catback and I'm finding it way too loud as there's no resonator on the cat back.
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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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wow and you're still saying it's too loud?.
I have a BCS DP and sport cat linked with a link pipe into milltek catback and I'm finding it way too loud as there's no resonator on the cat back.
Yeah still too loud, heard so many people say this system is slightly louder than stock just a nice deep rumble when driving normal but mines a lot louder and very intrusive in the car, but everyone that has said that have had the sports cat fitted on theirs that's what made me think it might make the difference!
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You could do with having a ride in a car with a sport cat Powervalve system fitted. One man's 'loud' is another man's 'subtle'.
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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 
yeah the BCS are massive compared to other cats on the market so possibly compensate for the restrictions and again are loud :signLOL: the de cat would still be less restrictive as you've mentioned giving more peak power as I've learnt over the years imho that is. :happy2:
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You could do with having a ride in a car with a sport cat Powervalve system fitted. One man's 'loud' is another man's 'subtle'.
I think that is exactly what I need mate! Would solve this in an instance lol will have to see if there's anyone in the Nottingham area with that set up!
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What system is louder prestige or powervalve I had a tb prestige system on my old car with sport cat not loud at all.
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What system is louder prestige or powervalve I had a tb prestige system on my old car with sport cat not loud at all.
The prestige power valve is the quieter one mate, I've got the sport power valve system but is decat not sports cat so wasn't sure wether that was the reason for being so loud or wether it was because it has the smaller silencer being the sport system. That might be my option to go prestige just trying to save the cost of buying a sports cat and a silencer!
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Ok mate thanks for that.
Like said above best seeing if someone can take you out in there car first before taking the plunge and wasting your money. Good luck
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Ok mate thanks for that.
Like said above best seeing if someone can take you out in there car first before taking the plunge and wasting your money. Good luck
Yeah I think that's my best option isn't it, cheers mate!
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Hi all, just thought I'd say after meeting up with a forum member today I can say a decat is ALOT louder than sports cat on the Bcs sports powervalve system, just thought I would say just in case anyone else is in the same boat as me! Thanks for all the help from people who replied :)
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De cat is obviously louder as it's just common sense as I'll say it again, there's no restriction but thank you for that information as others will find this a great deal of help deciding what they want :happy2:
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De cat is obviously louder as it's just common sense as I'll say it again, there's no restriction but thank you for that information as others will find this a great deal of help deciding what they want :happy2:
Yeah I did think that from the start tbh and then when you said it too I was pretty certain just wasn't sure how much difference in noise it made was really surprised, don't get me wrong it sounds awesome on a decat just not practical as a daily! I nearly bought a prestige silencer but changed my order to a sports cat after hearing a forum members system, sounds perfect!
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De cat is obviously louder as it's just common sense as I'll say it again, there's no restriction but thank you for that information as others will find this a great deal of help deciding what they want :happy2:
Yeah I did think that from the start tbh and then when you said it too I was pretty certain just wasn't sure how much difference in noise it made was really surprised, don't get me wrong it sounds awesome on a decat just not practical as a daily! I nearly bought a prestige silencer but changed my order to a sports cat after hearing a forum members system, sounds perfect!
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im lucky to have the milltek 2.75" or I bet mine would sound even louder than it is now :surprised: but still going to resonate it as I don't like the noise as my daily or in general eitherand that's mho :smiley: