Decats and the NCT

hey guys! thinking about decatting my B4! whether that be a H&S system delivered or a custom exhaust from the uk.

but what are the rules and regs with the NCT!? emissions? if the car came with a primary downpipe cat and a center pipe cat does i have to them for the NCT??

its not a problem if i do, ill just keep the standard in the shed and put it on prior!

thanks

you will need cat for nct......

and back box? what are the rules with loud back boxes?

less than 98db at two thirds max revs (about 5k) i think?????????????

[quote author=scoobyjoe link=topic=30324.msg350428#msg350428 date=1304449528]
you will need cat for nct......
[/quote]

one cat or two?? i have two! as above primary down and center

if i only need one i might just go for a center decat!

you say i need a cat, do you mean i will need it too keep emissions down? or need one physically there due to regs, regardless of emissions

i know with my impreza
i have to put the original don pipe with the cat inside every time i do a nct test to pass the emissions
and also now i will have to put the original exhaust on for noise reasons
although maybe a bung can be put in it instead

You need a cat installed in the car to pass emmissions. On the B4, the centre section alone will give you a pass. Throw some diptaine (from any motor factors) in for good measure when you are going and make sure the cat is well roasted when you get to the nct centre. Mine passed there recently with just the centre cat and i know of a few other with the same results. Saves major hassle having to replace the downpipe with seized bolts etc.

Put the standard centre back on with the standard backbox and noise will not be an issue. They won't even bother to test it because it won't be even close.

When replacing the exhaust, its probably easier to take the centre and backbox off in one piece, the backbox bolts will be corroded to shite so you'll be feckin ages trying to get them off. The spring loaded bolts holding the centre to the dowpipe are so much easier to deal with. Shouldn't take more than an hour to swap even on your first go

As for the straight through, definitely go for it .. I had a H&S full system on mine, lovely sound off them. Full straight through and specified that there was to be no narrowing in the pipe where the centre meets the backbox (No unnecessary restrictions thank you very much!!!). If you want to get the downpipe & centre pipe only, I have a 4.5" backbox there, 100% as it came from H&S, never even fitted to the car. I bought it to replace the 3.5" i had fitted but I sold the car on so now its just sitting there if you have any interest

hey bro!! thanks for the concise reply! thats the kind i was hoping for!!

it is my plan to go straight through, and by way of a full H&S system!

my problem is this! you say put back the standard center and backbox at the time of test, i dont have a standard one, the guy that had my car before me thought it a good idea to bodge on a Halfords special "Savage" universal backbox! and i mean REALLY bodge it one! if you saw the welding and scrap metal tube they used you would be sick! it has basically no sound deadening so is uber loud, so will fail the noise even before they rev the engine!

so in summery i need a new backbox (quite) for tests, unless i rip out the standard center pipe and chav backbox as a whole and then at test time put it back in with a bung in the backbox??

so what your saying is, with a primary decat with a center cat installed i should pass the emissions? will the standard center pipe bolt to a H&S decat primary down??

thanks for your knowledge mate

oh and how much do you want for the backbox??

You need to buy a 2nd hand centre section and back box.. for test use.. or get a loan of one.
Or you could buy a straight through system, with high flow cat in down pipe, and use a bung or bolt on a standard back box etc etc... you have few options... but you need some form of cat and not noisey exhaust regardless of how you do it....
Be carefull when decating.. Robbie or some Legacy head will know more but they may be a chance of over boost and fuel cut

already have the center pipe just the backbox is needed!! or as you say, a bung!

H&s Do bungs, it may be more expensive but a high flow cat is a fit and forget solution

murray motorsport
http://www.murraymotorsport.ie/products/hks-inner-muffler-silencer
someone else may know if this one works well
was thinking about getting one myself

[quote author=KENC link=topic=30324.msg350666#msg350666 date=1304541372]
H&s Do bungs, it may be more expensive but a high flow cat is a fit and forget solution
[/quote]

ALLOT more exspensive

[quote author=goosie208 link=topic=30324.msg350610#msg350610 date=1304529364]
my problem is this! you say put back the standard center and backbox at the time of test, i dont have a standard one, the guy that had my car before me thought it a good idea to bodge on a Halfords special "Savage" universal backbox! and i mean REALLY bodge it one! if you saw the welding and scrap metal tube they used you would be sick! it has basically no sound deadening so is uber loud, so will fail the noise even before they rev the engine!

so in summery i need a new backbox (quite) for tests, unless i rip out the standard center pipe and chav backbox as a whole and then at test time put it back in with a bung in the backbox??
[/quote]

Fook sake there are some dummies around .. If you go at the exhaust to take of the backbox, will you end up damaging the flange on the centre section? If you think you will, then I would just make a bung for the existing exhaust, there's no point in wrecking the centre section too and having to go buy a new centre and backbox. They are dead simple, I designed and got the lads in work to make one for my mate's type R, reduced the noise level from 110db to 55db. Or alternatively, you could buy one that might suit your exhaust but they are a very simple design so if you know anyone with metal fab experience, they could do it for you no bother.


[quote author=goosie208 link=topic=30324.msg350610#msg350610 date=1304529364]
so what your saying is, with a primary decat with a center cat installed i should pass the emissions? will the standard center pipe bolt to a H&S decat primary down??
[/quote]

Yes, you will pass emmissions providing the centre cat is in reasonably good condition. Still throw some diptaine in for good meaure at the time of the test.

On the B4 the centre pipe actually bolts to the secondary downpipe which end in a kind of a Y-shape. The primary downpipe bolts from the turbo on to the secondary downpipe and the centre pipe attaches to the secondary then. So really it won't be a problem, the primary H&S decat dowpipe is a perfect fit from the turbo to the secondary downpipe so no problems there.

As a side note, just FYI, a standard backbox won't bolt to a straight through H&S centre pipe as the flange is offset so the bolt holes don't meet up. It will only meet up with a H&S straight through backbox. If you get a standard replacement centre decat (i.e. with the narrowing) then that will fit to other standard fit backboxes but there's no point in that as it restricts the exhaust flow to 2" at the narrowing.

I assume if you are going full decat, then you'll be getting someone to map it? You can decat the centre and backbox completely with no problem but if you decat the downpipe, then you will need a map as it will cause boost spikes.

Looking for €280ono for the backbox as I know I won't ever get the money i paid for it, even if it is brand new & unused. They are £310 sterling(£260 plus VAT) plus shipping from H&S

Hope that helps

yeah i plan , and in very big inverted commas say "plan" on getting Bob Rawle to do it! weather that be at STI Tuning for a rediculass sum of money! (not their fault its just falling victim to circumstances) or get it done in the UK at BR Developments if and when im over there in the car,

you last post was a vital one! i hadn't realised that if i changed the center pipe i would HAVE to change to a H&S backbox! i was more concerned about the primary downpipe, but now you have explained that i can see exactly what your saying!

very interesting! thanks, ill have to see if the GF will allow such extravagant spending's at this time lol

It really depends on what you want, you have 2 options for the centre section:

1. If you get a straight through 2.5" centre pipe without a narrowing, then you will need the backbox which also has a 2.5" straight through pipe.

2. If you get a decat centre pipe as a standard replacement with the narrowing, then you can use a standard backbox. However, you will suffer performance losses as the narrowing means the pipe goes down to 2" at the joint which causes a big restriction.

As you will need a backbox anyway, I would go with the full 2.5" straight through system for that extra little bit of grunt

[quote author=goosie208 link=topic=30324.msg350610#msg350610 date=1304529364]
my problem is this! you say put back the standard center and backbox at the time of test, i dont have a standard one, the guy that had my car before me thought it a good idea to bodge on a Halfords special "Savage" universal backbox! and i mean REALLY bodge it one! if you saw the welding and scrap metal tube they used you would be sick! it has basically no sound deadening so is uber loud, so will fail the noise even before they rev the engine!
[/quote]

Snap! I had the exact same thing on my WRX when I bought it...Savage performance exhausts it said on a sticker on the backbox and it looked like it had been welded on by a blind man!!

Sorry to be the grim reaper but, the plod are shortly being issued with SPL testers (noise meters) that are to be used at the roadside so the whole swapping the system out for the NCT may not be viable much longer. Along with this they are also being issued with a device to determine the level of tint on the windows. I think it would be wise to see that one of the side effects of this is that they can stop you more easily than before. I'm not aware of the penalties but I suspect it will be in the form of fines, maybe to recoup the cost of the equipement or even as a revenue generating exercise. Suffice to say, when they roll it out it will be all over the forums.

They already have them!!

I was pulled over at the weekend for a go with this new technology. Was followed by a squad car down a street for about half a mile and then got the blue lights and pulled in. Guard told me about new limit of 99db and new meter for on the spot test. They hooked it up and I had to rev to 3,750rpm. It measured at 82.5 at tick over and at about 103 each time it reached 3,750 – we gave it 3 goes because the guard wanted to do one himself with his hand pressing down the accelerator!!!

I just said “Yes guard, no guard, 3 bags full guard” because I could see it was going to work out ok. I asked a few questions around why it had to be 3,750rpm and where they were placing the equipment, but I didn’t even get out to look as my wife was with me so wanted to keep it hassle free. At the end of it they told me I “would have to get something done about it”. I told him I had a bung at home that I had never used and that would make a huge difference. I have to have it sorted before I’m next in the place where it happened (about 90 miles from home)!!

My car has a full decat with Ninja II backbox from scoobyworld. The backbox was quiet when I got it, it’s the decat that made it loud. I was going to put it through the NCT with just the OEM downpipe back on, not using the bung!

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