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  1. LSBasi

    LSBasi Registered User

    Thanks to people like like DannyRS3 and Tartaris, I now know which direction I’m going with Tuning+mods (DP+Midpipe+MRC map) and what colour to order my car in today (Java Green).

    My question is probably flogging a dead horse to most of you guys but I’ll ask it anyway.

    Apart from the usual MOT issues and voiding warranty, are their any other cons to a decat over a sports cat?

    Does anybody regret going decat?

    Are the fumes and smells that extreme when stationary that it stinks the car out with windows down or sunroof open?

    Would anyone advise me against going decat?
    DannyRS3 likes this.
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  3. DannyRS3

    DannyRS3 Registered User

    There is no reason not to except a more noise (and drone, rasp and rattle), but you seem very keen on maximum volume so that's not likely an issue. For a daily driver, for some that might be a bit OTT. Yes, you will smell unburned petrol when standing behind the car admiring the sound, but no big deal there. It's not going to get inside the car unless you're idling it in the garage. :) Only downsides are legality if you live I an area where police care about such things, and come MOT time as you said. Might be a good idea to find a decated RS3 you can listen to before pulling the trigger, even youtube might help there.

    That said, you won't sacrifice much if any performance with high flow cats, and you won't have to faff in 2 years time at MOT. It'll also be a bit more civil sounding, but plenty aggressive with a tune.
  4. Tristan

    Tristan Registered User


    Hi, I went from just decat downpipes fmic and intake w/ mrc stage 2 map TO all the stated plus milltek non res catback.

    With the downpipes fmic and intake setup, everything was fine there was a clear noticeable difference with pops and bangs with the car in dynamic.

    Going to comfort mode (with the decat downpipes) was basically the same as stock comfort mode. Switching from dynamic to comfort felt like pressing a mute button ideal for when you are approaching a destination or your own neigborhood.

    You will need a map to soften the harsh cold starts though but since you're looking to get a map I would say full steam ahead with the decat downpipes. The non res cat back would be a step too far for you because being in dynamic is almost identical minus the higher revs as being in comfort mode with the cat back.
  5. LSBasi

    LSBasi Registered User

    The car will be a weekend toy so a loud startup and lots of 5 cylinder noise sounds great. Don’t get me wrong guys, if it wasn’t for the glorious 5 cylinder I wouldn’t be overly keen on increasing the volume

    Danny, seems I got the wrong end of the stick with the decat fumes

    Do you guys reckon the RS3 would pass an MOT with sports cat and no GPF filters? If yes, I’ll 100% head down the sports cat path
  6. Beebee-one

    Beebee-one Registered User

    If you are contemplating going for decat downpipes then I would assume you are going to get the car mapped? Just needed to ask as some people seem to think they can just fit the decat exhaust and that's it job done.
    As for the cons you are asking about......
    Firstly it's not a cheap job to do as it involves around 3 to 4 hrs of workshop time to fit a downpipe. Some garages will drop the front subframe and leave you with the extra hassle (and cost) of having to get a wheel alignment check afterwards (MRC use pins to reposition it so it is usually not a problem). Obviously if you are keeping the car past MOT time then choose your exhaust system wisely. There are a number of them where you can retro fit a sports cat without having to remove the whole damn thing and refit the OEM part to pass an MOT.
    I have a Scorpion full decat downpipe (FL car) but also bought the 200 cell sports cat which can easily be swapped in and out again with just two bolted clamps (see pics below). Prior to the Scorpion I had a Milltek decat installed on the car which can also have the sports cat section retro fitted but it aint cheap.
    Noise: You have a certain amount of control over the noise (either ASBO loud or subdued) by using the Dynamic or Auto/Comfort modes. Be warned that by adding a downpipe it will amplify the wastegate tinny rattle you get at coldstart and below 2800rpm in Auto or Comfort mode. Dynamic mode and any engine revs above 4000rpm will open the exhaust flaps and give you (and surrounding population) the glorious 5 cylinder noise we all love.
    Smell: Yes there is a smell of pungent exhaust gas/unburnt fuel but only in certain circumstances such as idling or queuing in traffic, multi-storey car parks and other enclosed spaces. When the car is moving there is no noticeable smell in the cabin.

    The Scorpion decat DP....... the red circle is the decat section that can easily be removed and replaced with a sports cat (see other pic below)

    .....and the 200 cell sports cat that can be inserted inserted into the DP for MOT time or if you dont like the smell of the full decat exhaust.
  7. LSBasi

    LSBasi Registered User

    Yes I’m well aware I’ll need a map to remove the CEL after removing the cat lol

    That’s a smart bit of kit from Scorpion! Very clever.

    In all honestly would you not find it easier to slip your MOT man an extra 50 quid come MOT time?

    I think removing the OPF and a sports cat down pipe will be sufficient, along with the MRC remap.

    This Apr system is what I have in mind
  8. Beebee-one

    Beebee-one Registered User

    The APR DP is a pricey bit of kit but looks good.........whatever you fit has to be better than the stock DP (pic below).
    When I choose the downpipe I was unsure about the smell so rather than being stuck with it and trying to find an MOT guy who likes performance cars I went for the option of being able to swap out the sports cat.

    The stock DP (FL car). Not great gas flow and has the cat right next to the turbo outlet.....good for emissions but not so good for thermal management when mapping.
  9. LSBasi

    LSBasi Registered User

    It’s more an Mot guy that likes money rather that performance lol

    APR is pricey but all I’m buying is downpipe, midpipe and the APR panel filter (something about K&N panel filters look like they don’t catch the smaller partials). Then the MRC map. Once it’s all done I’d like to think I’ll never have to spend another penny on performance.

    Well I say that but gearbox mapping is something I know nothing about. I can’t see any reason to get this done as the RS3 I “THOROUGHLY” test drive gave me instant up and downshifts (Much better gearbox than on my M2 Comp)
  10. banny650

    banny650 Registered User

    Got an STM decat for my OPF car
    LSBasi likes this.
  11. LSBasi

    LSBasi Registered User

    How much difference to sound did they make?

    Was that the only hardware replaced?

    Who mapped your car, how were the results?


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