Cat Removal question

Ciaran WRX

Ciaran WRX

Well-known member
ISDC Club Member
Hi Lads quick one for u stock 05 wrx (afterburner backbox and Cosworth panel filter) has 3 cats if i remove 1 will it still pass the nct? if it will which one should i remove its going for a remap soon and i dont wanta have to put em back on for test..

any help would be apreacited..
 
It should pass with just the main one in the downpipe (same as the jdm classics, so remove the center and up pipe cats
 
downpipe has x2 cats and is in x2 sections.

uppipe has one.

so best to get the decat downpipe in the 2 sections.

so fully decatted for map.

and nct time easy fit second cat section of downpipe back on.
 
or just get a sports cat and no messing come nct time . not a cheap item and not as free as full decat so its a compromise really
 
as dave said man get the downpipe and just remove for nct or ya could leave it with the cat in the up pipe as mine passed the nct with a decat downpipe so whatever is the best route for yourself :thumbsup:
 
Alright lads cheers fr info any idea who does sports cats? might just chuck her in for the remap the way she is upgrade the fuel pump ..she was right on the margin at last nct on emmisions with the 3 cats in so id say if i remove any it will fail next time
 
[quote author=Ciaran WRX link=topic=37237.msg426782#msg426782 date=1362677296]
Alright lads cheers fr info any idea who does sports cats? might just chuck her in for the remap the way she is upgrade the fuel pump ..she was right on the margin at last nct on emmisions with the 3 cats in so id say if i remove any it will fail next time
[/quote]

that might have been something else causing the emmisions to be high rather than the cats, could be an air leak on the exhaust/ inlet manifold
 
You aren't going to see much gain if you map it with cats, one could argue it will be a waste of money, you really won't even warrant a new pump.
 
yea know if i take out cats map will give me more bang per buck but as i said i dnt wanta have to go puttin cats back on at nct time is there no one else that thinks its a hassle haveing to take cats off then put back on?
any info on where sports cats can be bought would be great
i beleve that the sti dosent have the cat in uppipe? the one above the turbo so shurly if i got rid of that should still be legal with the other two cats in dwn pipe?
few mappers recon any cat removal and it wont pass emmisions?...
 
as i said above man i put my car in for the nct with a full decat down pipe and the cat still in the up pipe and it passed no bother i dont think its a hassle re fitting the cat come nct time not cnsidering the gains you get from doing it when it's fully mapped and running 110 % :thumbsup:
 
If you were running close to failing at nct time with the full std system then you've a possible proble you need diagnosed and fixed before goin mapping!

The lads above wont be leading you wrong with their advice!

I'd see about fixing the possible problem before mapping and wouldn't wast money mapping it standard!
 
Everyone is telling you the same thing but you dont want to hear it, Why bother mapping it if your not taking out the cats?
There is loads of bits around either here or the Uk, I seen an STI manifold and cat less up pipe for sale on another forum, think the sti up pipe was 50gbp.
You are at nothing just removing the one in uppipe on its own as you have opened up before turbo, but have restriction after the turbo.

If you re fit the downpipe cat on its own for nct that will pass emissions.

Japspeed UK sell sports cats.
But for the money you will pay, you would have a full straight though system bought 2nd hand..
Get involved in your car, dont be afraid of an hours work to fit a down pipe...
To me, in my opinion... 2 choices... Decat the car completely and map... or just leave it alone..
leaving the cats in and mapping Its like pain a hooker and only sucking her titty....:)
 
cheers lads im taking it all on board dnt worry i recon ill look into a down.pipe leave cat in up pipe and look into the fuel air sensor bussiness i think u got a point and hopefull with the cat still in uppipe it will pass nct
im.going to ask my mechanic how much to swap it out...
mabay a cobra dwn pipe or any other revomedations cat back pipe is stock at the moment...
 
Heres the last nct emissions

Lambda 1.02

Low idle co 0.06

High idle 0.06

1.03 Lambada is i fail is that right

any ideas lads..
 
Thanks for all the help lads u seriously know your stuff Yea ha kinda made sence when i typed it fr some reason i thought it was the high idle that was the problem so a dwn pipe removes two cats is that correct should be good on the co2 with the one left in the uppipe do u recon..was lookin on Scoobyworld Afterburner 2.5" Bore Wide Mouth De-cat Downpipe 2001-2005
£190.00 is this what u would get..

any ideas bout how to sort the lambda..
 
High lambda can be caused by a leaking exhaust and seeing as yours is just failing I'd say that is the issue or intake leaking
 
Cheers Dec

ive changed out that laser bb for a afterburner one after the nct so if it was the old exhaust new one will have it sorted
u dnt mean a leaking h gasket when u say leaking intake do u..
 
Also dec a slightly high lamda reading like that could be a failing lamda and will have it lean!
That's prob some of why your other results are so low! Although 3 cats will be helpin aswell!

Internet isn't really the place to diagnose it tho!
Check the full system for leaks (no matter how small they do matter) and if all is good then you possibly need to try a new lamda!

Having this right is important if goin mapping!
 
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