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Discussion Starter #1
Can anyone please help with advantages or issues I may have with De - catting my FN2.

Heard a few stories of it makes it run worse than stock ? And engine lights coming on etc ?

Is it very restrictive the cat on the FN2 or are they high flow sports cats anyway ?

After little but more noise and free up the gases on the way out ?

Is it worth or leave it ?

Cheers guys !
 

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Premium Member
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Discussion Starter #3
Sounds like that's a No then LOL !

Do you know mate if the FN2 runs a sports style cat as standard, I've been told there not too restrictive and are a high flow cat anyway ?

Cheers
 

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Don't give up so easily! First of all a decat pipe alone is pointless. But a proper decat race header with flash pro and a remap or even the generic group M map will give it some noticable mid range power. It's not illegal but then you have the dilemma of fitting a cat each year for the MOT to pass emissions. Some know friendly testers who will give a fake reading. Otherwise fitting a removable cat in the cat back is an option, you really need a milltek or something like that. If you just want a bit of power then you could always get a cat back instead a long with flash pro. It wouldn't gain as much power.


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I can tell you my experience with decated Tegiwa.
To me, it's all about your expectations - whether you prefer relative comfort or maximum performance. I thought I wanted the latter, so my Fn2 is, for now, equipped with Tegiwa decatted, followed by 3 inch single exit custom made exhaust. My plan is to supercharge, so my thinking was: "Let's prepare the car for bigger power"
And it's...inbearable. Motorway is hell, loud as f#@*(It's wonderfull for quick blasts, though :p)
Seriously, if you plan on using your car on daily basis, I strongly advise against anything bigger than 2.75. There is no reason for it anyway, my mechanic had built one of the fastest n/a FN2 in it's time, stroked k24/k20, and he did not find 2.75 dual exit to be restrictive at all.
As for decatting - i don't know whether it's noticable difference in performance, but you can certainly smell it, and other drivers around you can as well...my mate has been driving behind me the other day, and said that it smells like an old 2 stroke Wartburg :D And there is also the issue with MOT and police inspections.

I am srsly contemplating on getting rid of this drain pipe of an exhaust, losing (?) 3 bhp, and have a pleasent, stealthy hot HATCH again.
 

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I can tell you my experience with decated Tegiwa.
To me, it's all about your expectations - whether you prefer relative comfort or maximum performance. I thought I wanted the latter, so my Fn2 is, for now, equipped with Tegiwa decatted, followed by 3 inch single exit custom made exhaust. My plan is to supercharge, so my thinking was: "Let's prepare the car for bigger power"
And it's...inbearable. Motorway is hell, loud as f#@*(It's wonderfull for quick blasts, though :p)
Seriously, if you plan on using your car on daily basis, I strongly advise against anything bigger than 2.75. There is no reason for it anyway, my mechanic had built one of the fastest n/a FN2 in it's time, stroked k24/k20, and he did not find 2.75 dual exit to be restrictive at all.
As for decatting - i don't know whether it's noticable difference in performance, but you can certainly smell it, and other drivers around you can as well...my mate has been driving behind me the other day, and said that it smells like an old 2 stroke Wartburg :D And there is also the issue with MOT and police inspections.

I am srsly contemplating on getting rid of this drain pipe of an exhaust, losing (?) 3 bhp, and have a pleasent, stealthy hot HATCH again.

@musegroove :flute:
 

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250bhp.... finally :)
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How many silencers have you got mate?

The two silencer one is god awful loud and droney but the third was added on the tailpipe and quietens it down a fair bit from what I've heard. Also heard the K24 bottom end completely changes the exhaust note drastically (sounds deeper which may be why it's droning so much too; mixed with a 3").

I'm hoping with two silencers and a 200 CELL cat it will be loud but not abusively loud. Thankfully I don't do many miles @flashy so motorway drone won't be much of an issue, it drones like sh** at 4k anyway with the FD2 pump and mount inserts so I cruise at 60 lol :D
 

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Its pretty much a fact that I have the quietest custom 2.5" single exit ever made, by solid fabrications. As quiet as mine is, with a decat manifold I'm confident that a 3" version replica of mine could be made. But it needs to be planned and discussed with your custom exhaust fabricator, because otherwise you're typical 3" will. E very loud with a decat. The guy above is right, when you've had a loud exhaust it's truly wonderful to have a quiet and refined driving experience once again.


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Mine has got 2 silencers, one of which was 'restored' - filled with some kind of deadening material before exhaust was mounted;
About the third one - might be, but that would further restrict whole system, right? So why bother with such diameter in a first place. I have been told that 3" is fine on the track, where noise does not matter.
In city driving, you can live with it, if you want to keep it "quiet", you can feather the throttle and keep the rpm down due to low speeds.
But we both how responsive k20 is at ~ 2k rpm, so...you wind it up, and then it starts shouting.

Worst is 70-80 mph and throttle position more than 5%, cause it's just noise, it's not roar, it's not sporty burble, it's just headache.

That k24 was stroked to 2.6 or 2.7, and well over 300 bhp, so it moght have sounded different than internally stock k20, granted ;)
 

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250bhp.... finally :)
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Sounds alright then lol :)

I can't do 70-80mph with the FD2 pump as that range makes your ears bleed anyway.
Also won't mention that I'd kill for a K24 let alone a stroked one xD
 

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Not surprised 3 inch plus decat manifold is loud.

Even adding a sport cat probably won't quieten it down.

Adding a silencer shouldn't harm power. It's that or go 2.5 inch diameter. Only small power loss N/A maybe more of an issue when u supercharge, but better lose power than have a headache.
 

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Nobody read my post ! If you replicate my design then you can get solid fab to make a reasonably quiet 3", even with decat. 3 silencers is a must but you have to emphasise that they're as large as possible. Remind him of mine if you need some guidance. My main backbox is a bit larger than his typical 3" super silent back boxes. He's very good at getting silencers in the smallest places. Tracks do have limits and most 3" with decat would fail !




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