MK5 Golf GTI
All Things Mk5 => Mk5 General Area => Topic started by: Edition_30_P on March 13, 2011, 06:48:11 pm
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I'm stuck with whether I should stick with the decat Downpipe or get a hi flow sports cat? I've been doing some research and I've heard there isn't any benefits of a decat just hassle when it comes to MOT time?
Can anyone help me as I'm gonna pull my finger out and by next weekend have either one on my car!
Cheers,
Phil
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In all likelyhood a decat would fail the MOT.
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They mainly fail on cold start.... If warm they'll more than likely pass! Main thing I want to know is which would offer better performance and why?
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A decat WILL fail the MOT, but they do offer a performance advantage over a high-flow 'sports' cat. On stage2+ on a K04 based car we typically see 350-360hp but with a decat we have seen 370+. Logs show lower EGT's and the mapping usually allows a richer AFR with a few degrees more timing advance under full load.
However, I am yet to carry out a back to back test with both items on the same car.
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In all likelyhood a decat would fail the MOT.
....Most definitely: De-catting a car in the UK registered after 1993 is illegal as it will fail an emissions check.
Milltek offer a High-flow downpipe, not a de-cat (for legal road use).
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@PDT: thanks for that! I had PM'd you yesterday too!
@ Robin: Milltek do offer a decat system but, they obviously don't advertise it as they do with the hi flow sports cat!
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@ Robin: Milltek do offer a decat system but, they obviously don't advertise it as they do with the hi flow sports cat!
....I don't know for certain without asking them but think they probably do for competitive race cars only. I think they have more than one cell value available.
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I know a few guys running them on their S3's, TTRS's and Edition 30's! Just haven't seen them in action. Ompared to ones that are running hi flow sports cats! I've spoken to milltek with regards to this and they are very cheap too! I've done research and found that they are more likely to fail on an older car than say a car of about 10 years old! My mate at worl has a 2001 8L S3 with a decat milltek and his turbo sounds to spool a lot quicker than another mates milltek hi flow sports cat! They are actuallyalmost half the cost of the hi flow sports cat too!
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I had a Milltek 3" decat on a non res system - it wasn't so much any extra power I noticed compared to mate's sportscats, more that it revved like a bike! It spooled up and punched through to the redline so fast it was unreal.
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@ Tony_Danza: That sounds right up my street, mate :happy2: I've got the Decat sitting here ready to fit ans I've also located a 3" Hi Flow Sports Cat for the same money! Swaying towards keeping the Decat though :evilgrin:
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As long as you know the situation regarding the legality of it, then it's up to you.
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Of course!
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I'm in the same situation as you mate, a decat will fail the MOT - unless you have a friendly mechanic - but the sport cat is double the price! As far as performance goes as I understand the turbo will spool quicker with the decat and iirc hurdy posted some graphs which showed the power early on in the rev band was 90 bhp over the sports cat, and the torque curve was like Everest :surprised:
I will have a search and see if I can dig up the post. :happy2:
Edit: Have a butchers at this, particularly the second post by Hurdy. :happy2:
http://www.mk5golfgti.co.uk/forum/index.php/topic,10109.0.html
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Ceers, Pagey!!
Quickly read thru that and i'm 80% sold!
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Ceers, Pagey!!
Quickly read thru that and i'm 80% sold!
For 380 bhp I would sell my wifes soul to the devil! :signLOL:
I am having the precat filter removed from mine next month along with some other work, hopefully that should make an improvement over standard. :evilgrin:
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Decat certainly helped with an earlier spool up time on stage 1 map but I found it didn't really feel much different higher up the rpm. I would imagine a higher state of tune would make more use of it with the lower EGTs.
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For sure, you've got to have someone who understands the finest points of mapping to maximise the new-found flow's benefits.
Oh, and DSG bangs through a decat... :love:
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Thread resurrection!
Any one else gone down the route of sports cat or better still made the standard cat and decat removeable?
If so what have you done ecu map-wise ? Can you run the decat map with a cat safely ?
Also any one know the dimensions of the standard GTI exhaust ? Would it be much of a restriction for a stage 2, say if I get a 3" DP, decat mated to a standard system ? I'm not wanting any extra noise or drone. Been there, done that. Needs to be discrete.
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I've got a 3in Pipewerx downpipe& 200CEL sports cat with has a reducer and mated to my OEM cat back. It's soooo much more responsive, turbo lag between gears is pretty much non-existent.
I'm running stock map for now(only for another week) and it's fine, although long term I'd expect EML on the dash.
Decat will be louder and will give you a few more ponies, they also smell awful :sad1: (exhaust fumes). I'm more than happy with sports cat, and of course knowing it's legal.
Decat needs a stage 2 map to remove the EML and stop the car from overfuelling. Then there's the hassle at MOT time :sad1:
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For sure, you've got to have someone who understands the finest points of mapping to maximise the new-found flow's benefits.
Oh, and DSG bangs through a decat... :love:
+2
Niki from rtech mapped my R with a sportscat,he said if I go decat he can get around 20bhp more out of mine
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I had a 3" DP and 200 cel cat on my mk1 S3, it spooled up a lot quicker and held power better. Also improved the mpg on B road blasts and motorway runs, I was getting 33-34 mpg brim to brim figures, before it struggled to get low 30s. Sounded a lot deeper too. I monitored the EGTs and they were significantly lower.
I'm hoping for the same for my Mk5. Still not sure whether to get a cat bypass and make the cat removeable so it can be swapped out easily once a year. I have a limited budget, so will probably mate it to the standard exhaust. I'd get a BCS or Milltek otherwise. I also got plans for an uprated HPFP, IC and Helix clutch ..... but that's the best part of £2k :laugh: